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102-417: Hives frequently occur following an infection or as a result of an allergic reaction such as to medication, insect bites , or food. Psychological stress , cold temperature, or vibration may also be a trigger. In half of cases the cause remains unknown . Risk factors include having conditions such as hay fever or asthma . Diagnosis is typically based on appearance. Patch testing may be useful to determine

204-503: A TH2 -mediated immune response. Many bacteria and viruses elicit a TH1 -mediated immune response, which down-regulates TH2 responses. The first proposed mechanism of action of the hygiene hypothesis was that insufficient stimulation of the TH1 arm of the immune system leads to an overactive TH2 arm, which in turn leads to allergic disease. In other words, individuals living in too sterile an environment are not exposed to enough pathogens to keep

306-474: A runny nose , shortness of breath , or swelling. Note that food intolerances and food poisoning are separate conditions. Common allergens include pollen and certain foods. Metals and other substances may also cause such problems. Food, insect stings , and medications are common causes of severe reactions. Their development is due to both genetic and environmental factors. The underlying mechanism involves immunoglobulin E antibodies (IgE), part of

408-530: A T helper 2 (TH2)-predominant response driven by suppression of interleukin 12 by both the autonomic nervous system and the hypothalamic–pituitary–adrenal axis . Stress management in highly susceptible individuals may improve symptoms. Allergic diseases are more common in industrialized countries than in countries that are more traditional or agricultural, and there is a higher rate of allergic disease in urban populations versus rural populations, although these differences are becoming less defined. Historically,

510-1042: A benign condition called dermatographic urticaria . Hives can also be classified by the purported causative agent. Many different substances in the environment may cause hives, including medications, food and physical agents. In perhaps more than 50% of people with chronic hives of unknown cause, it is due to an autoimmune reaction. Risk factors include having conditions such as hay fever or asthma . Drugs that have caused allergic reactions evidenced as hives include codeine , sulphate of morphia , dextroamphetamine , aspirin , ibuprofen , penicillin , clotrimazole , trichazole, sulfonamides , anticonvulsants , cefaclor , piracetam , vaccines , and antidiabetic drugs . The antidiabetic sulphonylurea glimepiride , in particular, has been documented to induce allergic reactions manifesting as hives. The most common food allergies in adults are shellfish and nuts . The most common food allergies in children are shellfish , nuts, eggs , wheat , and soy . One study showed Balsam of Peru , which

612-413: A country grows more affluent and, it is presumed, cleaner. The use of antibiotics in the first year of life has been linked to asthma and other allergic diseases. The use of antibacterial cleaning products has also been associated with higher incidence of asthma, as has birth by caesarean section rather than vaginal birth. Chronic stress can aggravate allergic conditions. This has been attributed to

714-414: A day. Common side effects include headache, nausea, and dizziness. Serious side effects may include low blood sugar . Use during pregnancy and breastfeeding is not recommended. It works predominantly by increasing the amount of insulin released from the pancreas . It is classified as a second-generation sulfonylurea . Glimepiride was patented in 1979 and approved for medical use in 1995. It

816-401: A few days and without leaving any long-lasting skin changes. Cases of long duration are more common in females. Cases of short duration are more common among children while cases of long duration are more common among those who are middle aged. Fewer than 5% of cases last for more than six weeks. The condition frequently recurs. In half of cases of hives, the cause remains unknown . Angioedema

918-537: A first line therapy as they block both brain and peripheral H1 receptors, causing sedation. Second-generation antihistamines , such as loratadine , cetirizine , fexofenadine or desloratadine , selectively antagonize peripheral H1 receptors, and are less sedating, less anticholinergic , and generally preferred over the first-generation antihistamines. Fexofenadine, a new-generation antihistamine that blocks histamine H1 receptors, may be less sedating than some second-generation antihistamines. People who do not respond to

1020-424: A hard surface, etc. The areas of the body most commonly affected are the hands, feet, trunk, abdomen, buttocks, legs and face. Although this appears to be very similar to dermatographism, the cardinal difference is that the swelled skin areas do not become visible quickly and tend to last much longer. This form of the skin disease is, however, rare. Cholinergic urticaria (CU) is one of the physical urticaria which

1122-427: A hasty drop in body temperature. Regular antihistamines are not generally efficacious. One particular antihistamine, cyproheptadine (Periactin), has been found to be useful. The tricyclic antidepressant doxepin has been found to be effective blocking agents of histamine. Finally, a medication named ketotifen, which keeps mast cells from discharging histamine, has also been employed with widespread success. This form of

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1224-525: A hitherto unsuspected symbiosis is at work. For more information on this topic, see Helminthic therapy . In the initial stages of allergy, a type I hypersensitivity reaction against an allergen encountered for the first time and presented by a professional antigen-presenting cell causes a response in a type of immune cell called a T H 2 lymphocyte , a subset of T cells that produce a cytokine called interleukin-4 (IL-4). These T H 2 cells interact with other lymphocytes called B cells , whose role

1326-428: A large local reaction may occur in the form of an area of skin redness greater than 10 cm in size that can last one to two days. This reaction may also occur after immunotherapy . Risk factors for allergies can be placed in two broad categories, namely host and environmental factors. Host factors include heredity , sex, race , and age, with heredity being by far the most significant. However, there has been

1428-449: A licensed health care provider ( e.g. , an allergy specialist) or general practitioner. Unlike skin-prick testing, a blood test can be performed irrespective of age, skin condition, medication, symptom, disease activity, and pregnancy. Adults and children of any age can get an allergy blood test. For babies and very young children, a single needle stick for allergy blood testing is often gentler than several skin pricks. An allergy blood test

1530-418: A milk allergy will have a reaction to beef. Lactose intolerance, a common reaction to milk, is not a form of allergy at all, but due to the absence of an enzyme in the digestive tract . Those with tree nut allergies may be allergic to one or to many tree nuts , including pecans , pistachios , and walnuts . In addition, seeds , including sesame seeds and poppy seeds , contain oils in which protein

1632-401: A parasitic infection, such as blastocystosis and strongyloidiasis among others. The rash that develops from poison ivy , poison oak , and poison sumac contact is commonly mistaken for urticaria. This rash is caused by contact with urushiol and results in a form of contact dermatitis called urushiol-induced contact dermatitis . Urushiol is spread by contact but can be washed off with

1734-423: A patient in for evaluation, some allergists will prefer an initial blood test prior to performing the skin prick test. Skin tests may not be an option if the patient has widespread skin disease or has taken antihistamines in the last several days. Patch testing is a method used to determine if a specific substance causes allergic inflammation of the skin. It tests for delayed reactions. It is used to help ascertain

1836-454: A person with cholinergic urticaria will develop the characteristic small hives, especially on the neck and chest. The immediate symptoms of this type are treated with antihistamines, epinephrine and airway support. Taking antihistamines prior to exercise may be effective. Ketotifen is acknowledged to stabilise mast cells and prevent histamine release, and has been effective in treating this hives disorder. Avoiding exercise or foods that cause

1938-445: A process called degranulation , during which they release histamine and other inflammatory chemical mediators ( cytokines , interleukins , leukotrienes , and prostaglandins ) from their granules into the surrounding tissue causing several systemic effects, such as vasodilation , mucous secretion, nerve stimulation, and smooth muscle contraction. This results in rhinorrhea , itchiness, dyspnea, and anaphylaxis. Depending on

2040-440: A recent increase in the incidence of allergic disorders that cannot be explained by genetic factors alone. Four major environmental candidates are alterations in exposure to infectious diseases during early childhood, environmental pollution , allergen levels, and dietary changes. Dust mite allergy, also known as house dust allergy, is a sensitization and allergic reaction to the droppings of house dust mites . The allergy

2142-411: A reduction in their symptoms. Those with a longer disease duration typically have a worse prognosis, with greater symptom severity. Chronic urticaria is often accompanied by an intense pruritus, and other symptoms associated with a reduced quality of life and a high burden of co-morbid psychiatric conditions such as anxiety and depression. Chronic urticaria is usually seen in those older than 40 years, it

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2244-518: A strong grease- or oil-dissolving detergent and cool water and rubbing ointments. Dermatographic urticaria (also known as dermatographism or "skin writing") is marked by the appearance of weals or welts on the skin as a result of scratching or firm stroking of the skin. Seen in 4–5% of the population, it is one of the most common types of urticaria, in which the skin becomes raised and inflamed when stroked, scratched, rubbed, and sometimes even slapped. The skin reaction usually becomes evident soon after

2346-437: A systemic allergic response that is also called anaphylaxis; multiple organ systems can be affected, including the digestive system , the respiratory system , and the circulatory system . Depending on the severity, anaphylaxis can include skin reactions, bronchoconstriction, swelling , low blood pressure , coma, and death. This type of reaction can be triggered suddenly, or the onset can be delayed. The nature of anaphylaxis

2448-489: A vibrating device such as a laboratory vortex machine against the forearm for four minutes. Speedy swelling of the whole forearm extending into the upper arm is also noted later. The principal treatment is avoidance of vibratory stimulants. Antihistamines have also been proven helpful. The mainstay of therapy for both acute and chronic hives is education, avoiding triggers and using antihistamines. Chronic hives can be difficult to treat and lead to significant disability. Unlike

2550-428: Is inherited and related to an irregularity in the immune system, but the specific allergen is not. The risk of allergic sensitization and the development of allergies varies with age, with young children most at risk. Several studies have shown that IgE levels are highest in childhood and fall rapidly between the ages of 10 and 30 years. The peak prevalence of hay fever is highest in children and young adults and

2652-419: Is a concern in severe cases, as angioedema of the throat can be fatal. This very rare form of angioedema develops in response to contact with vibration. In vibratory angioedema, symptoms develop within two to five minutes after contact with a vibrating object and abate after about an hour. People with this disorder do not experience dermographism or pressure urticaria. Vibratory angioedema is diagnosed by holding

2754-459: Is a life-threatening condition. Treatment guidelines for the management of chronic hives have been published. According to the 2014 American practice parameters, treatment involves a stepwise approach. Step 1 consists of second generation, H1 receptor blocking antihistamines. Systemic glucocorticoids can also be used for episodes of severe disease but should not be used for long term due to their long list of side effects. Step 2 consists of increasing

2856-408: Is a related condition (also from allergic and nonallergic causes), though fluid leakage is from much deeper blood vessels in the subcutaneous or submucosal layers. Individual hives that are painful, last more than 24 hours, or leave a bruise as they heal are more likely to be a more serious condition called urticarial vasculitis . Hives caused by stroking the skin (often linear in appearance) are due to

2958-418: Is a sulfone antimicrobial agent and is thought to suppress prostaglandin and leukotriene activity. It is helpful in therapy-refractory cases and is contraindicated in people with G6PD deficiency. Sulfasalazine, a 5-ASA derivative, is thought to alter adenosine release and inhibit IgE mediated mast cell degranulation, Sulfasalazine is a good option for people with anemia who cannot take dapsone. Hydroxychloroquine

3060-533: Is also useful. For cases that last more than six weeks long term antihistamine therapy is indicated. Immunosuppressants such as omalizumab or cyclosporin may also be used. About 20% of people are affected at some point in their lives. Cases of short duration occur equally in males and females while cases of long duration are more common in females. Cases of short duration are more common among children while cases of long duration are more common among those who are middle aged. Hives have been described at least since

3162-808: Is an allergic contact dermatitis, a delayed hypersensitive reaction appearing as dry, crusted lesions. This reaction usually lasts 48–96 hours. Sweating or rubbing the area under the glove aggravates the lesions, possibly leading to ulcerations. Anaphylactic reactions occur most often in sensitive patients who have been exposed to a surgeon's latex gloves during abdominal surgery, but other mucosal exposures, such as dental procedures, can also produce systemic reactions. Latex and banana sensitivity may cross-react. Furthermore, those with latex allergy may also have sensitivities to avocado , kiwifruit, and chestnut. These people often have perioral itching and local urticaria . Only occasionally have these food-induced allergies induced systemic responses. Researchers suspect that

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3264-834: Is an antimalarial agent that suppresses T lymphocytes. It has a low cost however it takes longer than dapsone or sulfasalazine to work. Omalizumab was approved by the FDA in 2014 for people with hives 12 years old and above with chronic hives. It is a monoclonal antibody directed against IgE. Significant improvement in pruritus and quality of life was observed in a phase III, multicenter, randomized control trial. Immunosuppressants used for CU include cyclosporine, tacrolimus, sirolimus, and mycophenolate. Calcineurin inhibitors, such as cyclosporine and tacrolimus, inhibit cell responsiveness to mast cell products and inhibit T cell activity. They are preferred by some experts to treat severe symptoms. Sirolimus and mycophenolate have less evidence for their use in

3366-513: Is available as a generic medication . In 2022, it was the 64th most commonly prescribed medication in the United States, with more than 10   million prescriptions. Glimepiride is indicated to treat type 2 diabetes ; its mode of action is to increase insulin secretion by the pancreas. However it requires adequate insulin synthesis as prerequisite to treat appropriately. It is not used for type 1 diabetes because in type 1 diabetes

3468-414: Is available through most laboratories . A sample of the patient's blood is sent to a laboratory for analysis, and the results are sent back a few days later. Multiple allergens can be detected with a single blood sample. Allergy blood tests are very safe since the person is not exposed to any allergens during the testing procedure. Glimepiride Glimepiride is an antidiabetic medication within

3570-401: Is common and can trigger allergic reactions such as asthma, eczema , or itching .The mite's gut contains potent digestive enzymes (notably peptidase 1 ) that persist in their feces and are major inducers of allergic reactions such as wheezing . The mite's exoskeleton can also contribute to allergic reactions. Unlike scabies mites or skin follicle mites, house dust mites do not burrow under

3672-405: Is complete, with no interference from meals. Significant absorption can occur within one hour, and distribution is throughout the body, 99.5% bound to plasma protein. Metabolism is by oxidative biotransformation, it is hepatic and complete. First, the medication is metabolized to M 1 metabolite by CYP2C9 . M 1 possesses about 1 ⁄ 3 of pharmacological activity of glimepiride, yet it

3774-434: Is diagnosed by applying pressure by stroking or scratching the skin. The hives should develop within a few minutes. Unless the skin is highly sensitive and reacts continually, treatment is not needed. Taking antihistamines can reduce the response in cases that are annoying to the person. This type of hives can occur right away, precisely after a pressure stimulus or as a deferred response to sustained pressure being enforced to

3876-539: Is hereditary and becomes evident as hives all over the body 9 to 18 hours after cold exposure. The common form of cold urticaria demonstrates itself with the rapid onset of hives on the face, neck, or hands after exposure to cold. Cold urticaria is common and lasts for an average of five to six years. The population most affected is young adults, between 18 and 25 years old. Many people with the condition also have dermographism and cholinergic hives. Severe reactions can be seen with exposure to cold water; swimming in cold water

3978-472: Is identified. Diagnosis is typically based on the appearance. The cause of chronic hives can rarely be determined. Patch testing may be useful to determine the allergy. In some cases regular extensive allergy testing over a long period of time is requested in hopes of getting new insight. No evidence shows regular allergy testing results in identification of a problem or relief for people with chronic hives. Regular allergy testing for people with chronic hives

4080-409: Is in many processed foods, to be the most common cause of immediate contact urticaria. Another food allergy that can cause hives is alpha-gal allergy , which may cause sensitivity to milk and red meat. A less common cause is exposure to certain bacteria, such as Streptococcus species or possibly Helicobacter pylori . Hives including chronic spontaneous hives can be a complication and symptom of

4182-415: Is limited evidence for their efficacy. Oral glucocorticoids are effective in controlling symptoms of chronic hives. However, they have an extensive list of adverse effects, such as adrenal suppression, weight gain, osteoporosis, hyperglycemia, etc. Therefore, their use should be limited to a couple of weeks. In addition, one study found that systemic glucocorticoids combined with antihistamines did not hasten

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4284-479: Is more common in women. The prevalence of chronic urticaria is 0.23% in the United States. Allergy Allergies , also known as allergic diseases , are various conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever , food allergies , atopic dermatitis , allergic asthma , and anaphylaxis . Symptoms may include red eyes , an itchy rash , sneezing , coughing ,

4386-542: Is not itself a protein, acts as a hapten and chemically reacts with, binds to, and changes the shape of integral membrane proteins on exposed skin cells. The immune system does not recognize the affected cells as normal parts of the body, causing a T-cell -mediated immune response . Of these poisonous plants, sumac is the most virulent. The resulting dermatological response to the reaction between urushiol and membrane proteins includes redness, swelling, papules , vesicles , blisters , and streaking. Estimates vary on

4488-435: Is not recommended. Acute and chronic hives are visually indistinguishable on visual inspection alone. Angioedema is similar to hives, but in angioedema, the swelling occurs in a lower layer of the dermis than in hives, as well as in the subcutis. This swelling can occur around the mouth, eyes, in the throat, in the abdomen, or in other locations. Hives and angioedema sometimes occur together in response to an allergen , and

4590-631: Is not the causative factor. The condition was first distinguished in 1980. People with exercise urticaria (EU) experience hives, itchiness, shortness of breath and low blood pressure five to 30 minutes after beginning exercise. These symptoms can progress to shock and even sudden death. Jogging is the most common exercise to cause EU, but it is not induced by a hot shower, fever, or with fretfulness. This differentiates EU from cholinergic urticaria. EU sometimes occurs only when someone exercises within 30 minutes of eating particular foods, such as wheat or shellfish. For these individuals, exercising alone or eating

4692-455: Is often guided by relevant literature. In general, a positive response is interpreted when the wheal of an antigen is ≥3mm larger than the wheal of the negative control (eg, saline or glycerin). Some patients may believe they have determined their own allergic sensitivity from observation, but a skin test has been shown to be much better than patient observation to detect allergy. If a serious life-threatening anaphylactic reaction has brought

4794-453: Is often the practice for determining whether allergy to milk, egg, soy, and wheat have been outgrown, and the testing interval is extended to 2–3 years for allergy to peanut, tree nuts, fish, and crustacean shellfish. Results of follow-up testing can guide decision-making regarding whether and when it is safe to introduce or re-introduce allergenic food into the diet. Skin testing is also known as "puncture testing" and "prick testing" due to

4896-420: Is present, which may elicit an allergic reaction. Allergens can be transferred from one food to another through genetic engineering ; however, genetic modification can also remove allergens. Little research has been done on the natural variation of allergen concentrations in unmodified crops. Latex can trigger an IgE-mediated cutaneous, respiratory, and systemic reaction. The prevalence of latex allergy in

4998-512: Is presumed, exposed to more infectious agents through their siblings, than in children from families with only one child. It is used to explain the increase in allergic diseases that have been seen since industrialization, and the higher incidence of allergic diseases in more developed countries. The hygiene hypothesis has now expanded to include exposure to symbiotic bacteria and parasites as important modulators of immune system development, along with infectious agents. Epidemiological data support

5100-417: Is production of antibodies. Coupled with signals provided by IL-4, this interaction stimulates the B cell to begin production of a large amount of a particular type of antibody known as IgE. Secreted IgE circulates in the blood and binds to an IgE-specific receptor (a kind of Fc receptor called FcεRI ) on the surface of other kinds of immune cells called mast cells and basophils , which are both involved in

5202-439: Is provoked during sweating events such as exercise, bathing, staying in a heated environment, or emotional stress. The hives produced are typically smaller than classic hives and are generally shorter-lasting. Multiple subtypes have been elucidated, each of which require distinct treatment. The cold type of urticaria is caused by exposure of the skin to extreme cold, damp and windy conditions; it occurs in two forms. The rare form

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5304-466: Is saline or glycerin; positive is histamine). A small plastic or metal device is used to puncture or prick the skin. Sometimes, the allergens are injected "intradermally" into the patient's skin, with a needle and syringe. Common areas for testing include the inside forearm and the back. If the patient is allergic to the substance, then a visible inflammatory reaction will usually occur within 30 minutes. This response will range from slight reddening of

5406-453: Is such that the reaction can seem to be subsiding but may recur throughout a period of time. Substances that come into contact with the skin, such as latex , are also common causes of allergic reactions, known as contact dermatitis or eczema. Skin allergies frequently cause rashes , or swelling and inflammation within the skin, in what is known as a " weal and flare" reaction characteristic of hives and angioedema . With insect stings,

5508-762: Is termed scombroid food poisoning . Ingestion of free histamine released by bacterial decay in fish flesh may result in a rapid-onset, allergic-type symptom complex which includes hives. However, the hives produced by scombroid is reported not to include wheals. Chronic idiopathic hives has been anecdotally linked to stress since the 1940s. A large body of evidence demonstrates an association between this condition and both poor emotional well-being and reduced health-related quality of life . A link between stress and this condition has also been shown. Some cases have been thought to be due to stress, including an association between post-traumatic stress and chronic idiopathic hives. In most cases of chronic idiopathic urticaria , no cause

5610-449: Is termed an "allergic" reaction (which usually refers to type I hypersensitivity), its pathophysiology involves a reaction that more correctly corresponds to a type IV hypersensitivity reaction. In type IV hypersensitivity, there is activation of certain types of T cells (CD8+) that destroy target cells on contact, as well as activated macrophages that produce hydrolytic enzymes . Effective management of allergic diseases relies on

5712-494: Is the most common cause of a severe reaction. This can cause a massive discharge of histamine, resulting in low blood pressure, fainting, shock and even loss of life. Cold urticaria is diagnosed by dabbing an ice cube against the skin of the forearm for 1 to 5 minutes. A distinct hive should develop if a person has cold urticaria. This is different from the normal redness that can be seen in people without cold urticaria. People with cold urticaria need to learn to protect themselves from

5814-549: Is useful for some types of allergies such as hay fever and reactions to insect bites. Its use in food allergies is unclear. Allergies are common. In the developed world, about 20% of people are affected by allergic rhinitis, about 6% of people have at least one food allergy, and about 20% have or have had atopic dermatitis at some point in time. Depending on the country, about 1–18% of people have asthma. Anaphylaxis occurs in between 0.05–2% of people. Rates of many allergic diseases appear to be increasing. The word "allergy"

5916-485: Is usually to proteins in the white , rather than the yolk . Milk-protein allergies —distinct from lactose intolerance —are most common in children. Approximately 60% of milk-protein reactions are immunoglobulin E –mediated, with the remaining usually attributable to inflammation of the colon . Some people are unable to tolerate milk from goats or sheep as well as from cows, and many are also unable to tolerate dairy products such as cheese. Roughly 10% of children with

6018-502: The lungs , shortness of breath , coughing, and wheezing. Aside from these ambient allergens, allergic reactions can result from foods, insect stings , and reactions to medications like aspirin and antibiotics such as penicillin . Symptoms of food allergy include abdominal pain, bloating , vomiting, diarrhea , itchy skin, and hives . Food allergies rarely cause respiratory (asthmatic) reactions, or rhinitis . Insect stings, food, antibiotics , and certain medicines may produce

6120-407: The sulfonylurea class, primarily prescribed for the management of type 2 diabetes . It is regarded as a second-line option compared to metformin , due to metformin's well-established safety and efficacy. Use of glimepiride is recommended in conjunction with lifestyle modifications such as diet and exercise. It is taken by mouth, reaching a peak effect within three hours and lasting for about

6222-1011: The ability to make an accurate diagnosis. Allergy testing can help confirm or rule out allergies. Correct diagnosis, counseling, and avoidance advice based on valid allergy test results reduce the incidence of symptoms and need for medications, and improve quality of life. To assess the presence of allergen-specific IgE antibodies, two different methods can be used: a skin prick test, or an allergy blood test . Both methods are recommended, and they have similar diagnostic value. Skin prick tests and blood tests are equally cost-effective, and health economic evidence shows that both tests were cost-effective compared with no test. Early and more accurate diagnoses save cost due to reduced consultations, referrals to secondary care, misdiagnosis, and emergency admissions. Allergy undergoes dynamic changes over time. Regular allergy testing of relevant allergens provides information on if and how patient management can be changed to improve health and quality of life. Annual testing

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6324-410: The acute form, 50–80% of people with chronic hives have no identifiable triggers. But 50% of people with chronic hives will experience remission within 1 year. Overall, treatment is geared towards symptomatic management. Individuals with chronic hives may need other medications in addition to antihistamines to control symptoms. People who experience hives with angioedema require emergency treatment as this

6426-506: The acute inflammatory response. The IgE-coated cells, at this stage, are sensitized to the allergen. If later exposure to the same allergen occurs, the allergen can bind to the IgE molecules held on the surface of the mast cells or basophils. Cross-linking of the IgE and Fc receptors occurs when more than one IgE-receptor complex interacts with the same allergenic molecule and activates the sensitized cell. Activated mast cells and basophils undergo

6528-423: The allergy. Prevention is by avoiding whatever it is that causes the condition. Treatment is typically with antihistamines , with the second generation antihistamines such as fexofenadine , loratadine and cetirizine being preferred due to less risk of sedation and cognitive impairment. In refractory cases, corticosteroids or leukotriene inhibitors may also be used. Keeping the environmental temperature cool

6630-536: The blood. Certain microbe-sensing proteins , known as Toll-like receptors , found on the surface of cells in the body are also thought to be involved in these processes. Parasitic worms and similar parasites are present in untreated drinking water in developing countries, and were present in the water of developed countries until the routine chlorination and purification of drinking water supplies. Recent research has shown that some common parasites, such as intestinal worms (e.g., hookworms ), secrete chemicals into

6732-401: The body's immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine . Diagnosis is typically based on a person's medical history . Further testing of the skin or blood may be useful in certain cases. Positive tests, however, may not necessarily mean there is a significant allergy to

6834-403: The cause of skin contact allergy or contact dermatitis . Adhesive patches, usually treated with several common allergic chemicals or skin sensitizers, are applied to the back. The skin is then examined for possible local reactions at least twice, usually at 48 hours after application of the patch, and again two or three days later. An allergy blood test is quick and simple and can be ordered by

6936-857: The common cold. They usually appear three to five days after the cold has started, and may even appear a few days after the cold has resolved. Mechanisms other than allergen-antibody interactions are known to cause histamine release from mast cells. Many drugs, for example morphine , can induce direct histamine release not involving any immunoglobulin molecule. Also, a diverse group of signaling substances called neuropeptides , have been found to be involved in emotionally induced hives. Dominantly inherited cutaneous and neurocutaneous porphyrias ( porphyria cutanea tarda , hereditary coproporphyria , variegate porphyria and erythropoietic protoporphyria ) have been associated with solar urticaria . The occurrence of drug-induced solar urticaria may be associated with porphyrias. This may be caused by IgG binding, not IgE. This

7038-680: The cross-reactivity of latex with banana, avocado , kiwifruit , and chestnut occurs because latex proteins are structurally homologous with some other plant proteins. About 10% of people report that they are allergic to penicillin ; however, of that 10%, 90% turn out not to be. Serious allergies only occur in about 0.03%. One of the main sources of human allergies is insects. An allergy to insects can be brought on by bites, stings, ingestion, and inhalation. Another non-food protein reaction, urushiol-induced contact dermatitis , originates after contact with poison ivy , eastern poison oak , western poison oak , or poison sumac . Urushiol , which

7140-485: The delayed establishment of gut flora in infants . However, the research to support this theory is conflicting, with some studies performed in China and Ethiopia showing an increase in allergy in people infected with intestinal worms. Clinical trials have been initiated to test the effectiveness of certain worms in treating some allergies. It may be that the term 'parasite' could turn out to be inappropriate, and in fact

7242-508: The disease occurs on areas of the skin exposed to the sun; the condition becomes evident within minutes of exposure. This type of urticaria is also termed rare and occurs upon contact with water. The response is not temperature-dependent and the skin appears similar to the cholinergic form of the disease. The appearance of hives is within one to 15 minutes of contact with the water and can last from 10 minutes to two hours. This kind of hives does not seem to be stimulated by histamine discharge like

7344-642: The dose of the current antihistamine, adding other antihistamines, or adding a leukotriene receptor antagonist such as montelukast. Step 3 consists of adding or replacing the current treatment with hydroxyzine or doxepin. If the individual doesn't respond to steps 1–3 then they are considered to have refractory symptoms. At this point, anti-inflammatory medications (dapsone, sulfasalazine), immunosuppressants (cyclosporin, sirolimus) or other medications like omalizumab can be used. These options are explained in more detail below. First generation antihistamines, such as diphenhydramine or hydroxyzine , are not recommended as

7446-588: The general population is believed to be less than one percent. In a hospital study, 1 in 800 surgical patients (0.125 percent) reported latex sensitivity, although the sensitivity among healthcare workers is higher, between seven and ten percent. Researchers attribute this higher level to the exposure of healthcare workers to areas with significant airborne latex allergens, such as operating rooms, intensive-care units, and dental suites. These latex-rich environments may sensitize healthcare workers who regularly inhale allergenic proteins. The most prevalent response to latex

7548-466: The gut wall (and, hence, the bloodstream) that suppress the immune system and prevent the body from attacking the parasite. This gives rise to a new slant on the hygiene hypothesis theory—that co-evolution of humans and parasites has led to an immune system that functions correctly only in the presence of the parasites. Without them, the immune system becomes unbalanced and oversensitive. In particular, research suggests that allergies may coincide with

7650-460: The hygiene hypothesis. Studies have shown that various immunological and autoimmune diseases are much less common in the developing world than the industrialized world, and that immigrants to the industrialized world from the developing world increasingly develop immunological disorders in relation to the length of time since arrival in the industrialized world. Longitudinal studies in the third world demonstrate an increase in immunological disorders as

7752-462: The immune system busy. Since our bodies evolved to deal with a certain level of such pathogens, when they are not exposed to this level, the immune system will attack harmless antigens, and thus normally benign microbial objects—like pollen—will trigger an immune response. The hygiene hypothesis was developed to explain the observation that hay fever and eczema , both allergic diseases, were less common in children from larger families, which were, it

7854-496: The incidence of asthma is highest in children under 10. Ethnicity may play a role in some allergies; however, racial factors have been difficult to separate from environmental influences and changes due to migration . It has been suggested that different genetic loci are responsible for asthma, to be specific, in people of European , Hispanic , Asian , and African origins. Allergic diseases are caused by inappropriate immunological responses to harmless antigens driven by

7956-459: The individual, allergen, and mode of introduction, the symptoms can be system-wide (classical anaphylaxis) or localized to specific body systems. Asthma is localized to the respiratory system and eczema is localized to the dermis . After the chemical mediators of the acute response subside, late-phase responses can often occur. This is due to the migration of other leukocytes such as neutrophils , lymphocytes , eosinophils , and macrophages to

8058-441: The initial site. The reaction is usually seen 2–24 hours after the original reaction. Cytokines from mast cells may play a role in the persistence of long-term effects. Late-phase responses seen in asthma are slightly different from those seen in other allergic responses, although they are still caused by release of mediators from eosinophils and are still dependent on activity of T H 2 cells. Although allergic contact dermatitis

8160-449: The injuring food without exercising produces no symptoms. EU can be diagnosed by having the person exercise and then observing the symptoms. This method must be used with caution and only with the appropriate resuscitative measures at hand. EU can be differentiated from cholinergic urticaria by the hot water immersion test. In this test, the person is immersed in water at 43 °C (109.4 °F). Someone with EU will not develop hives, while

8262-480: The maximum dose of H1 antihistamines may benefit from increasing the dose further, then to switching to another non-sedating antihistamine, then to adding a leukotriene antagonist , then to using an older antihistamine, then to using systemic steroids and finally to using ciclosporin or omalizumab . Steroids are often associated with rebound hives once discontinued. H2-receptor antagonists are sometimes used in addition to H1-antagonists to treat urticaria, but there

8364-440: The mentioned symptoms is very important. In particular circumstances, tolerance can be brought on by regular exercise, but this must be under medical supervision. The skin lesions of urticarial disease are caused by an inflammatory reaction in the skin, causing leakage of capillaries in the dermis , and resulting in an edema which persists until the interstitial fluid is absorbed into the surrounding cells. Hives are caused by

8466-415: The most common food allergy in adults or children. Severe or life-threatening reactions may be triggered by other allergens and are more common when combined with asthma. Rates of allergies differ between adults and children. Children can sometimes outgrow peanut allergies. Egg allergies affect one to two percent of children but are outgrown by about two-thirds of children by the age of 5. The sensitivity

8568-470: The other physical hives. Most researchers believe this condition is actually skin sensitivity to additives in the water, such as chlorine. Water urticaria is diagnosed by dabbing tap water and distilled water to the skin and observing the gradual response. Aquagenic urticaria is treated with capsaicin (Zostrix) administered to the chafed skin. This is the same treatment used for shingles . Antihistamines are of questionable benefit in this instance since histamine

8670-410: The pancreas is not able to produce insulin. Its use is contraindicated in patients with hypersensitivity to glimepiride or other sulfonylureas. Side effects from taking glimepiride include gastrointestinal tract (GI) disturbances, occasional allergic reactions, and rarely blood production disorders including thrombocytopenia , leukopenia , and hemolytic anemia . In the initial weeks of treatment,

8772-493: The population fraction that will have an immune system response. Approximately 25% of the population will have a strong allergic response to urushiol. In general, approximately 80–90% of adults will develop a rash if they are exposed to 0.0050 mg (7.7 × 10  gr) of purified urushiol, but some people are so sensitive that it takes only a molecular trace on the skin to initiate an allergic reaction. Allergic diseases are strongly familial ; identical twins are likely to have

8874-679: The release of histamine and other mediators of inflammation ( cytokines ) from cells in the skin. This process can be the result of an allergic or nonallergic reaction, differing in the eliciting mechanism of histamine release. Histamine and other proinflammatory substances are released from mast cells in the skin and tissues in response to the binding of allergen -bound IgE antibodies to high-affinity cell surface receptors. Basophils and other inflammatory cells are also seen to release histamine and other mediators, and are thought to play an important role, especially in chronic urticarial diseases. Over half of all cases of chronic idiopathic hives are

8976-618: The release of insulin by pancreatic beta cells and by inducing increased activity of intracellular insulin receptors. Not all secondary sulfonylureas have the same risk of hypoglycemia. Glibenclamide (glyburide) is associated with an incidence of hypoglycemia of up to 20–30%, compared to as low as 2% to 4% with glimepiride. Glibenclamide also interferes with the normal homeostatic suppression of insulin secretion in reaction to hypoglycemia, whereas glimepiride does not. Also, glibenclamide diminishes glucagon secretion in reaction to hypoglycemia, whereas glimepiride does not. Gastrointestinal absorption

9078-512: The result of an autoimmune trigger. Roughly 50% of people with chronic urticaria spontaneously develop autoantibodies directed at the receptor FcεRI located on skin mast cells. Chronic stimulation of this receptor leads to chronic hives. People with hives often have other autoimmune conditions, such as autoimmune thyroiditis , celiac disease , type 1 diabetes , rheumatoid arthritis , Sjögren's syndrome or systemic lupus erythematosus . Hive-like rashes commonly accompany viral illnesses, such as

9180-581: The risk of hypoglycemia may be increased. Alcohol consumption and exposure to sunlight should be restricted because they can worsen side effects. Nonsteroidal anti-inflammatory drugs (such as salicylates ), sulfonamides , chloramphenicol , coumadin and probenecid may potentiate the hypoglycemic action of glimepiride. Thiazides , other diuretics , phothiazides, thyroid products, oral contraceptives, and phenytoin tend to produce hyperglycemia . Like all sulfonylureas , glimepiride acts as an insulin secretagogue . It lowers blood sugar by stimulating

9282-479: The same allergic diseases about 70% of the time; the same allergy occurs about 40% of the time in non-identical twins . Allergic parents are more likely to have allergic children and those children's allergies are likely to be more severe than those in children of non-allergic parents. Some allergies, however, are not consistent along genealogies ; parents who are allergic to peanuts may have children who are allergic to ragweed . The likelihood of developing allergies

9384-404: The scratching and disappears within 30 minutes. Dermatographism is the most common form of a subset of chronic hives, acknowledged as "physical hives". It stands in contrast to the linear reddening that does not itch seen in healthy people who are scratched. In most cases, the cause is unknown, although it may be preceded by a viral infection, antibiotic therapy, or emotional upset. Dermatographism

9486-408: The series of tiny punctures or pricks made into the patient's skin. Tiny amounts of suspected allergens and/or their extracts ( e.g. , pollen, grass, mite proteins, peanut extract) are introduced to sites on the skin marked with pen or dye (the ink/dye should be carefully selected, lest it cause an allergic response itself). A negative and positive control are also included for comparison (eg, negative

9588-537: The skin and are not parasitic. A wide variety of foods can cause allergic reactions, but 90% of allergic responses to foods are caused by cow's milk, soy , eggs, wheat, peanuts, tree nuts , fish, and shellfish. Other food allergies, affecting less than 1 person per 10,000 population, may be considered "rare". The most common food allergy in the US population is a sensitivity to crustacea . Although peanut allergies are notorious for their severity, peanut allergies are not

9690-435: The skin to a full-blown hive (called "wheal and flare") in more sensitive patients similar to a mosquito bite . Interpretation of the results of the skin prick test is normally done by allergists on a scale of severity, with +/− meaning borderline reactivity, and 4+ being a large reaction. Increasingly, allergists are measuring and recording the diameter of the wheal and flare reaction. Interpretation by well-trained allergists

9792-524: The skin. In the deferred form, the hives only appear after about six hours from the initial application of pressure to the skin. Under normal circumstances, these hives are not the same as those witnessed with most urticariae. Instead, the protrusion in the affected areas is typically more spread out. The hives may last from eight hours to three days. The source of the pressure on the skin can happen from tight fitted clothing, belts, clothing with tough straps, walking, leaning against an object, standing, sitting on

9894-405: The substance in question. Early exposure of children to potential allergens may be protective. Treatments for allergies include avoidance of known allergens and the use of medications such as steroids and antihistamines . In severe reactions, injectable adrenaline (epinephrine) is recommended. Allergen immunotherapy , which gradually exposes people to larger and larger amounts of allergen,

9996-732: The time of Hippocrates . The term urticaria is from the Latin urtica meaning " nettle ". Hives, or urticaria, is a form of skin rash with red, raised, itchy bumps. They may also burn or sting. Hives can appear anywhere on the surface of the skin. Whether the trigger is allergic or not, a complex release of inflammatory mediators, including histamine from cutaneous mast cells , results in fluid leakage from superficial blood vessels. Hives may be pinpoint in size or several inches in diameter, they can be individual or confluent, coalescing into larger forms. About 20% of people are affected. Cases of short duration occur equally in males and females, lasting

10098-611: The time to symptom control compared with antihistamines alone. Leukotrienes are released from mast cells along with histamine. The medications, montelukast and zafirlukast block leukotriene receptors and can be used as add on treatment or in isolation for people with CU. It is important to note that these medications may be more beneficial for people with NSAID induced CU. Other options for refractory symptoms of chronic hives include anti-inflammatory medications, omalizumab, and immunosuppressants. Potential anti-inflammatory agents include dapsone, sulfasalazine, and hydroxychloroquine. Dapsone

10200-404: The treatment of chronic hives but reports have shown them to be efficacious. Immunosuppressants are generally reserved as the last line of therapy for severe cases due to their potential for serious adverse effects. In those with chronic urticaria, defined as either continuous or intermittent symptoms lasting longer than 6 weeks, 35% of people are symptom free 1 year after treatment, while 29% have

10302-548: The trees planted in urban areas were predominantly male to prevent litter from seeds and fruits, but the high ratio of male trees causes high pollen counts, a phenomenon that horticulturist Tom Ogren has called " botanical sexism ". Alterations in exposure to microorganisms is another plausible explanation, at present, for the increase in atopic allergy . Endotoxin exposure reduces release of inflammatory cytokines such as TNF-α , IFNγ , interleukin-10 , and interleukin-12 from white blood cells ( leukocytes ) that circulate in

10404-413: Was first used by Clemens von Pirquet in 1906. Many allergens such as dust or pollen are airborne particles. In these cases, symptoms arise in areas in contact with air, such as the eyes, nose, and lungs. For instance, allergic rhinitis, also known as hay fever, causes irritation of the nose, sneezing, itching, and redness of the eyes. Inhaled allergens can also lead to increased production of mucus in

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