Type of antigen that produces an abnormally vigorous immune response
This article is about the antigen. For the Irish-registered pharmaceutical company, seeAllergan.
Anallergen is an otherwise harmless substance that triggers anallergic reaction in sensitive individuals by stimulating animmune response.
In technical terms, an allergen is anantigen that is capable of stimulating atype-I hypersensitivity reaction inatopic individuals throughimmunoglobulin E (IgE) responses.[1] Most humans mount significant Immunoglobulin E responses only as a defense againstparasitic infections. However, some individuals may respond to many common environmental antigens. This hereditary predisposition is calledatopy. In atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity.[citation needed]
Sensitivities vary widely from one person (or from one animal) to another. A very broad range of substances can be allergens to sensitive individuals.
The United StatesFood and Drug Administration recognizes nine foods as major food allergens: peanuts, tree nuts, eggs, milk, shellfish, fish, wheat, soy, and most recently sesame,[4] as well as sulfites (chemical-based, often found in flavors and colors in foods) at 10ppm and over.[citation needed] In other countries, due to differences in the genetic profiles of their citizens and different levels of exposure to specific foods, the official allergen lists will vary. Canada recognizes all nine of the allergens recognized by the US as well as mustard.[5] TheEuropean Union additionally recognizes othergluten-containing cereals as well as celery andlupin.[6]
Another allergen isurushiol, a resin produced bypoison ivy andpoison oak, which causes the skin rash condition known asurushiol-induced contact dermatitis by changing a skin cell's configuration so that it is no longer recognized by the immune system as part of the body. Various trees and wood products such as paper, cardboard, MDF etc. can also cause mild to severe allergy symptoms through touch or inhalation of sawdust such as asthma and skin rash.[7]
An allergic reaction can be caused by any form of direct contact with the allergen—consuming food or drink one is sensitive to (ingestion), breathing in pollen, perfume or pet dander (inhalation), or brushing a body part against an allergy-causing plant (direct contact). Other common causes of serious allergy arewasp,[8]fire ant[9] andbee stings,[10]penicillin,[11] andlatex.[12] An extremely serious form of an allergic reaction is calledanaphylaxis.[13] One form of treatment is the administration of sterileepinephrine to the person experiencing anaphylaxis, which suppresses the body's overreaction to the allergen, and allows for the patient to be transported to a medical facility.[14]
Seasonal allergy symptoms are commonly experienced during specific parts of the year, usually during spring, summer or fall when certain trees or grasses pollinate. This depends on the kind of tree or grass. For instance, some trees such asoak,elm, andmaple pollinate in the spring, while grasses such asBermuda, timothy and orchard pollinate in the summer.
Grass allergy is generally linked to hay fever because their symptoms and causes are somehow similar to each other. Symptoms includerhinitis, which causessneezing and arunny nose, as well asallergic conjunctivitis, which includes watering and itchy eyes.[17] Also an initial tickle on the roof of the mouth or in the back of the throat may be experienced.
Also, depending on the season, the symptoms may be more severe and people may experiencecoughing,wheezing, and irritability. A few people even become depressed, lose theirappetite, or have problems sleeping.[18] Moreover, since thesinuses may also become congested, some people experienceheadaches.[19]
If both parents have had allergies in the past, there is a 66% chance for the individual to experience seasonal allergies, and the risk lowers to 60% if just one parent has had allergies.[20] The immune system also has strong influence on seasonal allergies, because it reacts differently to diverse allergens like pollen. When an allergen enters the body of an individual that is predisposed to allergies, it triggers an immune reaction and the production of antibodies. These allergen antibodies migrate to mast cells lining the nose, eyes, and lungs. When an allergen drifts into the nose more than once, mast cells release a slew of chemicals or histamines that irritate and inflame the moist membranes lining the nose and produce the symptoms of an allergic reaction: scratchy throat, itching, sneezing and watery eyes. Some symptoms that differentiate allergies from a cold include:[21]
No fever.
Mucous secretions are runny and clear.
Sneezes occurring in rapid and several sequences.
Itchy throat, ears and nose.
These symptoms usually last longer than 7–10 days.
Among seasonal allergies, there are some allergens that fuse together and produce a new type of allergy. For instance, grass pollen allergens cross-react with food allergy proteins in vegetables such as onion, lettuce, carrots, celery, and corn. Besides, the cousins of birch pollen allergens, like apples, grapes, peaches, celery, and apricots, produce severe itching in the ears and throat. The cypress pollen allergy brings a cross reactivity between diverse species like olive, privet, ash and Russian olive tree pollen allergens. In some rural areas, there is another form of seasonal grass allergy, combining airborne particles of pollen mixed with mold.[22]Recent research has suggested that humans might develop allergies as a defense to fight off parasites. According to Yale University ImmunologistRuslan Medzhitov, protease allergens cleave the same sensor proteins that evolved to detect proteases produced by the parasitic worms.[23] Additionally, a new report on seasonal allergies called "Extreme allergies and Global Warming", have found that many allergy triggers are worsening due to climate change. 16 states in the United States were named as "Allergen Hotspots" for large increases in allergenic tree pollen if global warming pollution keeps increasing. Therefore, researchers on this report claimed that global warming is bad news for millions of asthmatics in the United States whose asthma attacks are triggered by seasonal allergies.[24] Seasonal allergies are one of the main triggers for asthma, along with colds or flu, cigarette smoke and exercise. In Canada, for example, up to 75% of asthmatics also have seasonal allergies.[25]
Based on the symptoms seen on the patient, the answers given in terms of symptom evaluation and a physical exam, doctors can make a diagnosis to identify if the patient has a seasonal allergy. After performing the diagnosis, the doctor is able to tell the main cause of the allergic reaction and recommend the treatment to follow. 2 tests have to be done in order to determine the cause: a blood test and a skin test. Allergists do skin tests in one of two ways: either dropping some purified liquid of the allergen onto the skin and pricking the area with a small needle; or injecting a small amount of allergen under the skin.[26]
Alternative tools are available to identify seasonal allergies, such as laboratory tests, imaging tests, and nasal endoscopy. In the laboratory tests, the doctor will take a nasal smear and it will be examined microscopically for factors that may indicate a cause: increased numbers of eosinophils (white blood cells), which indicates an allergic condition. If there is a high count of eosinophils, an allergic condition might be present.[27]
Another laboratory test is the blood test for IgE (immunoglobulin production), such as theradioallergosorbent test (RAST) or the more recent enzyme allergosorbent tests (EAST), implemented to detect high levels of allergen-specific IgE in response to particular allergens. Although blood tests are less accurate than the skin tests, they can be performed on patients unable to undergo skin testing. Imaging tests can be useful to detect sinusitis in people who have chronic rhinitis, and they can work when other test results are ambiguous. There is also nasal endoscopy, wherein a tube is inserted through the nose with a small camera to view the passageways and examine any irregularities in the nose structure. Endoscopy can be used for some cases of chronic or unresponsive seasonal rhinitis.[28]
In 1952basidiospores were described as being possible airborne allergens[29] and were linked to asthma in 1969.[30] Basidiospores are the dominant airborne fungal allergens. Fungal allergies are associated with seasonal asthma.[31][32] They are considered to be a major source of airborne allergens.[33] The basidospore family include mushrooms, rusts, smuts, brackets, andpuffballs. The airborne spores from mushrooms reach levels comparable to those of mold and pollens. The levels of mushroom respiratory allergy are as high as 30 percent of those with allergic disorder, but it is believed to be less than 1 percent of food allergies.[34][35] Heavy rainfall (which increases fungal spore release) is associated with increased hospital admissions of children with asthma.[36] A study in New Zealand found that 22 percent of patients with respiratory allergic disorders tested positive for basidiospores allergies.[37] Mushroom spore allergies can cause either immediate allergic symptomatology or delayed allergic reactions. Those with asthma are more likely to have immediate allergic reactions and those with allergic rhinitis are more likely to have delayed allergic responses.[38] A study found that 27 percent of patients were allergic to basidiomycete mycelia extracts and 32 percent were allergic to basidiospore extracts, thus demonstrating the high incidence of fungal sensitisation in individuals with suspected allergies.[39] It has been found that of basidiomycete cap, mycelia, and spore extracts that spore extracts are the most reliable extract for diagnosing basidiomycete allergy.[40][41]
In Canada, 8% of children attending allergy clinics were found to be allergic toGanoderma, a basidiospore.[42]Pleurotus ostreatus,[43]cladosporium,[44] andCalvatia cyathiformis are significant airborne spores.[33] Other significant fungal allergens includeaspergillus andalternaria-penicillin families.[45] In IndiaFomes pectinatus is a predominant air-borne allergen affecting up to 22 percent of patients with respiratory allergies.[46] Some fungal air-borne allergens such asCoprinus comatus are associated with worsening ofeczematous skin lesions.[47] Children who are born during autumn months (during fungal spore season) are more likely to develop asthmatic symptoms later in life.[48]
Treatment includesover-the-counter medications,antihistamines,nasal decongestants,allergy shots, andalternative medicine. In the case of nasal symptoms,antihistamines are normally the first option. They may be taken together withpseudoephedrine to help relieve a stuffy nose and they can stop the itching and sneezing. Some over-the-counter options areBenadryl andTavist. However, these antihistamines may cause extreme drowsiness, therefore, people are advised to not operate heavy machinery or drive while taking this kind of medication. Other side effects include drymouth, blurred vision,constipation, difficulty withurination, confusion, and light-headedness.[49] There is also a newersecond generation of antihistamines that are generally classified as the "non-sedating antihistamines" or anti-drowsy, which includecetirizine,loratadine, andfexofenadine.[50]
An example ofnasal decongestants is pseudoephedrine and its side-effects includeinsomnia,restlessness, and difficulty urinating. Some othernasal sprays are available by prescription, includingAzelastine andIpratropium. Some of their side-effects include drowsiness. For eye symptoms, it is important to first bath the eyes with plain eyewashes to reduce the irritation. People should not wearcontact lenses during episodes of conjunctivitis.
Allergen immunotherapy treatment involves administering doses of allergens to accustom the body to induce specific long-term tolerance.[51] Allergy immunotherapy can be administered orally (as sublingual tablets or sublingual drops), or by injections under the skin (subcutaneous).[52][53] Immunotherapy contains a small amount of the substance that triggers the allergic reactions.[54]
Ladders are also used for egg and milk allergies as a home-based therapy mainly for children.[55][56] Such methods cited in the UK involve the gradual introduction of the allergen in a cooked form where the protein allergenicity has been reduced to become less potent.[57][58][59] By reintroducing the allergen from a fully cooked, usually baked, state research suggests that a tolerance can emerge to certain egg and milk allergies under the supervision of a dietitian or specialist.[60][61][55] The suitability of this treatment is debated between UK and North American experts.[55]
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^Rosmilah M, Shahnaz M, Patel G, Lock J, Rahman D, Masita A, et al. (December 2008). "Characterization of major allergens of royal jelly Apis mellifera".Tropical Biomedicine.25 (3):243–251.PMID19287364.
^Zug KA, Warshaw EM, Fowler JF, Maibach HI, Belsito DL, Pratt MD, et al. (2009). "Patch-test results of the North American Contact Dermatitis Group 2005-2006".Dermatitis: Contact, Atopic, Occupational, Drug.20 (3):149–60.PMID19470301.
^Fernandez J."Seasonal Allergies".The Merck Manual. Rahway, NJ, USA: Merck & Co., Inc.Archived from the original on 12 April 2010. Retrieved9 April 2010.
^Hasnain SM, Wilson JD, Newhook FJ (May 1985). "Fungal allergy and respiratory disease".The New Zealand Medical Journal.98 (778):342–346.PMID3858721.
^Levetin E (April 1989). "Basidiospore identification".Annals of Allergy.62 (4):306–310.PMID2705657.
^abHorner WE, Lopez M, Salvaggio JE, Lehrer SB (1991). "Basidiomycete allergy: identification and characterization of an important allergen from Calvatia cyathiformis".International Archives of Allergy and Applied Immunology.94 (1–4):359–361.doi:10.1159/000235403.PMID1937899.
^Sprenger JD, Altman LC, O'Neil CE, Ayars GH, Butcher BT, Lehrer SB (December 1988). "Prevalence of basidiospore allergy in the Pacific Northwest".The Journal of Allergy and Clinical Immunology.82 (6):1076–1080.doi:10.1016/0091-6749(88)90146-7.PMID3204251.
^Hasnain SM, Wilson JD, Newhook FJ, Segedin BP (May 1985). "Allergy to basidiospores: immunologic studies".The New Zealand Medical Journal.98 (779):393–396.PMID3857522.
^Santilli J, Rockwell WJ, Collins RP (September 1985). "The significance of the spores of the Basidiomycetes (mushrooms and their allies) in bronchial asthma and allergic rhinitis".Annals of Allergy.55 (3):469–471.PMID4037433.
^Weissman DN, Halmepuro L, Salvaggio JE, Lehrer SB (1987). "Antigenic/allergenic analysis of basidiomycete cap, mycelia, and spore extracts".International Archives of Allergy and Applied Immunology.84 (1):56–61.doi:10.1159/000234398.PMID3623711.
^Dhillon M (May 1991). "Current status of mold immunotherapy".Annals of Allergy.66 (5):385–392.PMID2035901.
^Gupta SK, Pereira BM, Singh AB (March 1999). "Fomes pectinatis: an aeroallergen in India".Asian Pacific Journal of Allergy and Immunology.17 (1):1–7.PMID10403002.
^Van Overtvelt L. et al. Immune mechanisms of allergen-specific sublingual immunotherapy. Revue française d'allergologie et d'immunologie clinique. 2006; 46: 713–720.
^Bloom KA, Huang FR, Bencharitiwong R, Bardina L, Ross A, Sampson HA, et al. (December 2014). "Effect of heat treatment on milk and egg proteins allergenicity".Pediatric Allergy and Immunology.25 (8):740–746.doi:10.1111/pai.12283.PMID25251921.
^Venter C, Meyer R, Ebisawa M, Athanasopoulou P, Mack DP (January 2022). Eigenmann PA (ed.). "Food allergen ladders: A need for standardization".Pediatric Allergy and Immunology.33 (1): e13714.doi:10.1111/pai.13714.PMID34882843.
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