View source for Allergen

{{short description|Type of antigen that produces an abnormally vigorous immune response}}
{{about|the antigen|the Irish-registered pharmaceutical company|Allergan}}
{{Use dmy dates|date=August 2015}}
{{cs1 config|name-list-style=vanc|display-authors=6}}
An '''allergen''' is an otherwise harmless substance that triggers an [[allergic reaction]] in sensitive individuals by stimulating an [[immune response]].

In technical terms, an allergen is an [[antigen]] that is capable of stimulating a [[type-I hypersensitivity]] reaction in [[atopy|atopic]] individuals through [[immunoglobulin E]] (IgE) responses.<ref>{{cite book | vauthors = Goldsby RA, Kindt TJ, Kuby J, Osborne BA |title=Immunology |date=2003 |publisher=W.H. Freeman |location=New York |isbn=978-0-7167-4947-9 |edition=5th}}</ref> Most humans mount significant immunoglobulin E responses only as a defense against [[parasitic infection]]s. However, some individuals may respond to many common environmental antigens. In atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity.{{citation needed|date=March 2022}}

Sensitivities vary widely from one person (or from one animal) to another. A very broad range of substances can be allergens to sensitive individuals.

== Examples ==

[[File:Misc pollen.jpg|thumb|240px|right|[[Scanning electron microscope|SEM]] of miscellaneous plant pollens. Pollens are very common allergens.]]

[[File:House Dust Mite.jpg|thumb|240px|right|The [[house dust mite]], its feces and [[chitin]] are common allergens]]

Allergens can be found in a variety of sources, such as [[dust mite]] excretion, [[pollen]], pet [[dander]], or even [[royal jelly]].<ref>{{cite journal | vauthors = Rosmilah M, Shahnaz M, Patel G, Lock J, Rahman D, Masita A, Noormalin A | title = Characterization of major allergens of royal jelly Apis mellifera | journal = Tropical Biomedicine | volume = 25 | issue = 3 | pages = 243–251 | date = December 2008 | pmid = 19287364 }}</ref> Food allergies are not as common as [[food sensitivity]], but some foods such as [[peanut]]s (a [[legume]]), [[Nut (fruit)|nut]]s, [[seafood]] and [[shellfish]] are the cause of serious allergies in many people.<ref>{{Cite journal |last1=Francis |first1=Olivia L. |last2=Wang |first2=Kathleen Y. |last3=Kim |first3=Edwin H. |last4=Moran |first4=Timothy P. |date=2020-09-01 |title=Common food allergens and cross-reactivity |journal=Journal of Food Allergy |language=en |volume=2 |issue=1 |pages=17–21 |doi=10.2500/jfa.2020.2.200020 |issn=2689-0267 |pmc=11250430 |pmid=39022146}}</ref>

The United States [[Food and Drug Administration]] recognizes nine foods as major food allergens: peanuts, tree nuts, eggs, milk, shellfish, fish, wheat, soy, and most recently sesame,<ref>{{Cite web | work = Center for Food Safety and Applied Nutrition |date=2023-01-10 |title=Food Allergies |url=https://www.fda.gov/food/food-labeling-nutrition/food-allergies |archive-url=https://web.archive.org/web/20201110155745/https://www.fda.gov/food/food-labeling-nutrition/food-allergies |archive-date=10 November 2020 |access-date=2023-12-23 |publisher = U.S. Food and Drug Administration (FDA) |language=en}}</ref> as well as sulfites (chemical-based, often found in flavors and colors in foods) at 10ppm and over.{{Citation needed|date=December 2023}} 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.<ref>{{cite web|url=http://www.inspection.gc.ca/english/fssa/labeti/allerg/20110216inde.shtml |title = Revised Labelling Regulations for Food Allergens, Gluten Sources and Sulphites (Amendments to the Food and Drug Regulations) | work = Canadian Food Inspection Agency (CFIA) |access-date=28 February 2011 |archive-url=https://web.archive.org/web/20110222005144/http://www.inspection.gc.ca/english/fssa/labeti/allerg/20110216inde.shtml |archive-date=22 February 2011 }}</ref> The [[European Union]] additionally recognizes other [[gluten|gluten-containing cereals]] as well as celery and [[lupinus|lupin]].<ref>{{Cite web |title=Food Allergens - European Union | work = Food Allergy Research and Resource Program (FARRP) | publisher = University of Nebraska–Lincoln |url=https://farrp.unl.edu/ref-sit-eu |access-date=2024-06-23 }}</ref>

Another allergen is [[urushiol]], a resin produced by [[poison-ivy (plant)|poison ivy]] and [[poison oak]], which causes the skin rash condition known as [[urushiol-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 board|MDF]] etc. can also cause mild to severe allergy symptoms through touch or inhalation of sawdust such as asthma and skin rash.<ref>{{cite web |url=http://www.wood-database.com/wood-articles/wood-allergies-and-toxicity/ |title=Wood Allergies and Toxicity |publisher=The Wood Database |access-date=24 April 2014 |url-status=live |archive-url=https://web.archive.org/web/20140502174208/http://www.wood-database.com/wood-articles/wood-allergies-and-toxicity |archive-date=2 May 2014 }}</ref>

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 are [[wasp]],<ref>{{cite journal | vauthors = dos Santos-Pinto JR, dos Santos LD, Arcuri HA, da Silva Menegasso AR, Pêgo PN, Santos KS, Castro FM, Kalil JE, De-Simone SG, Palma MS | title = B-cell linear epitopes mapping of antigen-5 allergen from Polybia paulista wasp venom | journal = The Journal of Allergy and Clinical Immunology | volume = 135 | issue = 1 | pages = 264–267 | date = January 2015 | pmid = 25129676 | doi = 10.1016/j.jaci.2014.07.006 | doi-access = free | hdl = 11449/129399 | hdl-access = free }}</ref> [[fire ant]]<ref>{{cite journal | vauthors = Zamith-Miranda D, Fox EG, Monteiro AP, Gama D, Poublan LE, de Araujo AF, Araujo MF, Atella GC, Machado EA, Diaz BL | title = The allergic response mediated by fire ant venom proteins | journal = Scientific Reports | volume = 8 | issue = 1 | article-number = 14427 | date = September 2018 | pmid = 30258210 | pmc = 6158280 | doi = 10.1038/s41598-018-32327-z | bibcode = 2018NatSR...814427Z }}</ref> and [[bee]] stings,<ref>{{Cite journal| vauthors = de Lima PR, Brochetto-Braga MR |date=2003|title=Hymenoptera venom review focusing on Apis mellifera|journal=Journal of Venomous Animals and Toxins Including Tropical Diseases|volume=9|issue=2|doi=10.1590/S1678-91992003000200002|issn=1678-9199|doi-access=free}}</ref> [[penicillin]],<ref>{{Cite web| vauthors = Solensky R | veditors = Phillips EJ, Feldweg AM | title = Penicillin allergy: Immediate reactions | url= https://www.uptodate.com/contents/penicillin-allergy-immediate-reactions| work = UpToDate |access-date=2019-06-25}}</ref> and [[Latex allergy|latex]].<ref>{{Cite journal |last1=Nucera |first1=Eleonora |last2=Aruanno |first2=Arianna |last3=Rizzi |first3=Angela |last4=Centrone |first4=Michele |date=2020-09-28 |title=Latex Allergy: Current Status and Future Perspectives |journal=Journal of Asthma and Allergy |language=English |volume=13 |pages=385–398 |doi=10.2147/JAA.S242058|doi-access=free |pmid=33061465 |pmc=7532063 |hdl=10807/161325 |hdl-access=free }}</ref>  An extremely serious form of an allergic reaction is called [[anaphylaxis]].<ref>{{Citation |last1=McLendon |first1=Kevin |title=Anaphylaxis |date=2025 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK482124/ |access-date=2025-01-21 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29489197 |last2=Sternard |first2=Britni T.}}</ref> One form of treatment is the administration of sterile [[epinephrine]] 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.<ref>{{Citation |last1=McLendon |first1=Kevin |title=Anaphylaxis |date=2025 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK482124/ |access-date=2025-01-21 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29489197 |last2=Sternard |first2=Britni T.}}</ref>

Although allergic reactions typically require prior sensitization to a specific allergen, clinical symptoms can sometimes occur upon first exposure to a food or substance; this is explained by IgE cross-reactivity, where prior sensitization to structurally homologous proteins from other sources leads the immune system to recognize similar proteins in the new allergen as triggers, even though the affected individual has never previously consumed or contacted it.<ref>{{Cite journal |title=IgE-based analysis of sensitization and cross-reactivity to yellow mealworm and edible insect allergens before their widespread dietary introduction |author=Majsiak, Emilia; Choina, Magdalena; Gromek, Weronika; Wykrota, Julia; Kozłowska, Danuta; Swadźba, Jakub; Cukrowska, Bożena; Kowal, Krzysztof |journal=Scientific Reports |year=2025 |volume=15 |issue=1 |article-number=1466 |doi=10.1038/s41598-024-83645-4 |pmid=39789064 |pmc=11718154 |bibcode=2025NatSR..15.1466E }}</ref>

== Common ==
[[File:Peanuts, Egg, and Milk (33000737773).jpg|thumb|Common food allergens]]
{{main|List of allergens}}
{{div col|colwidth=20em}}
In addition to foreign proteins found in foreign serum (from [[blood transfusion]]s) and [[vaccine]]s, common allergens include:
* Animal products
** [[Fel d 1]] ([[allergy to cats]])
** [[fur]] and [[dander]]
** [[cockroach]] [[calyx (zoology)#Insects|calyx]]
** [[wool]]
** [[dust mite]] excretion
* [[Drug allergy|Drug]]s
** [[penicillin]]
** [[Sulfonamide (medicine)|sulfonamides]]
** [[salicylate]]s (also found naturally in numerous [[fruit]]s)
* [[Food allergy|Food]]s
** [[celery]] and [[celeriac]]<ref>{{cite journal | vauthors = Bublin M, Radauer C, Wilson IB, Kraft D, Scheiner O, Breiteneder H, Hoffmann-Sommergruber K | title = Cross-reactive N-glycans of Api g 5, a high molecular weight glycoprotein allergen from celery, are required for immunoglobulin E binding and activation of effector cells from allergic patients | journal = FASEB Journal | volume = 17 | issue = 12 | pages = 1697–1699 | date = September 2003 | pmid = 12958180 | doi = 10.1096/fj.02-0872fje | url = http://www.fasebj.org/cgi/content/full/17/12/1697 | url-status = live | s2cid = 22253513 | doi-access = free | archive-url = https://web.archive.org/web/20070104224624/http://www.fasebj.org/cgi/content/full/17/12/1697 | archive-date = 4 January 2007 | url-access = subscription }}</ref>
** [[maize|corn]] or [[maize]]
** [[egg allergy|egg]]s (typically [[Egg white|albumen]], the egg white)
** [[fruit allergy|fruit]]
*** [[pumpkin]], [[eggplant]]
** [[legume]]s
*** [[bean]]s
*** [[pea]]s
*** [[peanut allergy|peanut]]s
*** [[soybean]]s
** [[milk allergy|milk]]
** [[seafood allergy|seafood]]
** [[sesame]]
** [[soy allergy|soy]]
** [[nut allergy|tree nut]]s
*** [[pecan]]s
*** [[almond]]s
** [[wheat allergy|wheat]]
* [[Insect sting allergy|Insect sting]]s
** [[bee]] sting [[venom (poison)|venom]]
** [[wasp]] sting venom
** [[mosquito]] bites
* Mold [[spore]]s
* Top 5 allergens discovered in [[patch test]]s in 2005–06:
** [[nickel sulfate]] (19.0%)
** [[balsam of Peru]] (11.9%)
** [[fragrance]] mix I (11.5%)
** [[quaternium-15]] (10.3%), and
** [[neomycin]] (10.0%).<ref name="autogenerated2005">{{cite journal | vauthors = Zug KA, Warshaw EM, Fowler JF, Maibach HI, Belsito DL, Pratt MD, Sasseville D, Storrs FJ, Taylor JS, Mathias CG, Deleo VA, Rietschel RL, Marks J | title = Patch-test results of the North American Contact Dermatitis Group 2005-2006 | journal = Dermatitis: Contact, Atopic, Occupational, Drug | volume = 20 | issue = 3 | pages = 149–60 | date = 2009 | pmid = 19470301 | doi = | url = }}</ref>
* Metals
** [[nickel]]
** [[chromium]]
* Other
** [[latex allergy|latex]]
** [[wood]]
* Plant [[pollen]]s ([[hay fever]])
** [[grass]]{{snd}}[[ryegrass]], [[timothy-grass]]
** [[weed]]s{{snd}}[[ragweed]], [[plantago]], [[Urtica|nettle]], ''[[Artemisia vulgaris]]'', ''[[Chenopodium album]]'', [[sorrel]]
** [[tree]]s{{snd}}[[birch]], [[alder]], [[hazel]], [[hornbeam]], ''[[Aesculus]]'', [[willow]], [[Populus|poplar]], ''[[Platanus]]'', ''[[Tilia]]'', ''[[Olea]]'', [[Ashe juniper]], ''Alstonia scholaris''
{{Div col end}}

== Seasonal ==
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 as [[oak]], [[elm]], and [[maple]] pollinate in the spring, while grasses such as [[Cynodon dactylon|Bermuda]], [[Timothy (grass)|timothy]] and [[Orchard grass|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 include [[rhinitis]], which causes [[sneezing]] and a [[runny nose]], as well as [[allergic conjunctivitis]], which includes watering and itchy eyes.<ref name="Seasonal Allergy">{{cite web |url=http://seasonalallergies.us/ |title=Seasonal Allergy — What to Know | work = Seasonal Allergy |access-date=9 April 2010 |archive-url=https://web.archive.org/web/20100414063236/http://seasonalallergies.us/ |archive-date=14 April 2010 }}</ref> 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 experience [[coughing]], [[wheezing]], and irritability. A few people even become depressed, lose their [[appetite]], or have problems sleeping.<ref>{{cite journal | pmc=9618478 | date=2022 | title=Efficacy of Proactive Topical Antihistamine Use in Patients with Seasonal Allergic Conjunctivitis | journal=Advances in Therapy | volume=39 | issue=12 | pages=5568–5581 | doi=10.1007/s12325-022-02324-w | pmid=36244054 | vauthors = Fukushima A, Miyazaki D, Kishimoto H, Ebihara N }}</ref> Moreover, since the [[sinuses]] may also become congested, some people experience [[headaches]].<ref name="Merck">{{cite web | vauthors = Fernandez J | work =The Merck Manual | publisher = Merck & Co., Inc. | location = Rahway, NJ, USA |url=http://www.merck.com/mmhe/sec16/ch185/ch185b.html |title=Seasonal Allergies
|access-date=9 April 2010| archive-url= https://web.archive.org/web/20100412052011/http://www.merck.com/mmhe/sec16/ch185/ch185b.html| archive-date= 12 April 2010 | url-status= live}}</ref>

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.<ref>{{Cite journal |last1=Ober |first1=Carole |last2=Yao |first2=Tsung-Chieh |date=2011 |title=The genetics of asthma and allergic disease: a 21st century perspective |journal=Immunological Reviews |language=en |volume=242 |issue=1 |pages=10–30 |doi=10.1111/j.1600-065X.2011.01029.x |issn=1600-065X |pmc=3151648 |pmid=21682736}}</ref> 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:<ref>{{cite web | url = https://www.cbc.ca/news/health/seasonal-allergies-something-to-sneeze-at-1.930532 | title = Seasonal allergies: Something to sneeze at | archive-url = https://web.archive.org/web/20100902081131/http://www.cbc.ca/health/story/2010/03/19/f-seasonal-allergies-symptoms.html | archive-date = 2 September 2010 | work = CBS News | url-status = live | access-date = 31 August 2010 }}</ref>
* 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]], [[Fraxinus|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]].<ref>{{cite web | url = http://www.seasonalallergies.us/ | title = Seasonal Allergies: What to know | archive-url = https://web.archive.org/web/20100414063236/http://seasonalallergies.us/ | archive-date=14 April 2010 | work = Seasonal Allergy | access-date = 31 August 2010 }}</ref>
Recent research has suggested that humans might develop allergies as a defense to fight off parasites. According to Yale University Immunologist [[Ruslan Medzhitov]], protease allergens cleave the same sensor proteins that evolved to detect proteases produced by the parasitic worms.<ref>{{cite web | url = http://www.abc.net.au/science/articles/2010/04/12/2870397.htm/ | title = Parasites behind seasonal allergies | archive-url = https://web.archive.org/web/20100908113331/http://www.abc.net.au/science/articles/2010/04/12/2870397.htm | archive-date=8 September 2010 | work = ABC Science | date = 12 April 2010 | access-date = 31 August 2010 }}</ref> 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.<ref>{{cite web | vauthors = Weinmann A | date = 14 April 2010 | url = http://www.nwf.org/News-and-Magazines/Media-Center/News-by-Topic/Global-Warming/2010/04-14-10-Seasonal-Allergies-Getting-Worse-From-Climate-Change.aspx/ | title = Seasonal allergies getting worse from Climate Change | archive-url = https://web.archive.org/web/20100806132853/http://www.nwf.org/News-and-Magazines/Media-Center/News-by-Topic/Global-Warming/2010/04-14-10-Seasonal-Allergies-Getting-Worse-From-Climate-Change.aspx | archive-date=6 August 2010 | work = National Wildlife Federation. Media Center.| access-date = 31 August 2010 }}</ref> 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.<ref>{{cite web | url = http://www.asthma.ca/allergies/asthmaandallergiessymptoms.html/ | title = Asthma and Allergies: The Symptoms | archive-url = https://web.archive.org/web/20100917191419/http://asthma.ca/allergies/asthmaandallergiessymptoms.html | archive-date=17 September 2010 | work = Asthma Society of Canada | access-date = 31 August 2010 }}</ref>

=== Diagnosis ===

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. Two 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.<ref>{{cite web | url = http://kidshealth.org/parent/medical/allergies/seasonal_allergies.html/ | title = Seasonal Allergies | archive-url = https://web.archive.org/web/20100516031605/http://kidshealth.org/parent/medical/allergies/seasonal_allergies.html | archive-date=16 May 2010 | work = Kids Health | access-date = 31 August 2010 }}</ref>

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.<ref>{{Cite web | vauthors = Liesveld J |title=Eosinophilia - Hematology and Oncology |url=https://www.merckmanuals.com/professional/hematology-and-oncology/eosinophilic-disorders/eosinophilia |access-date=2022-06-01 |website=Merck Manuals Professional Edition |language=en-US}}</ref>

Another laboratory test is the blood test for IgE (immunoglobulin production), such as the [[radioallergosorbent 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.<ref>{{cite news | url = http://health.nytimes.com/health/guides/disease/allergic-rhinitis/diagnosis.html | title = Allergic Rhinitis | archive-url = https://web.archive.org/web/20100904064016/http://health.nytimes.com/health/guides/disease/allergic-rhinitis/diagnosis.html | archive-date=4 September 2010 | work = New York Times Health Guide | access-date = 31 August 2010 }}</ref>

== Fungal ==
In 1952 [[Basidiospore|basidiospores]] were described as being possible airborne allergens<ref>{{cite journal | vauthors = Gregory PH, Hirst JM | title = Possible role of basidiospores as air-borne allergens | journal = Nature | volume = 170 | issue = 4323 | page = 414 | date = September 1952 | pmid = 12993181 | doi = 10.1038/170414a0 | s2cid = 4205965 | bibcode = 1952Natur.170..414G | doi-access = free }}</ref> and were linked to asthma in 1969.<ref>{{cite journal | vauthors = Herxheimer H, Hyde HA, Williams DA | title = Allergic asthma caused by basidiospores | journal = Lancet | volume = 2 | issue = 7612 | pages = 131–133 | date = July 1969 | pmid = 4183245 | doi = 10.1016/s0140-6736(69)92441-6 }}</ref> Basidiospores are the dominant airborne fungal allergens. Fungal allergies are associated with seasonal asthma.<ref>{{cite journal | vauthors = Hasnain SM, Wilson JD, Newhook FJ | title = Fungal allergy and respiratory disease | journal = The New Zealand Medical Journal | volume = 98 | issue = 778 | pages = 342–346 | date = May 1985 | pmid = 3858721 }}</ref><ref>{{cite journal | vauthors = Levetin E | title = Basidiospore identification | journal = Annals of Allergy | volume = 62 | issue = 4 | pages = 306–310 | date = April 1989 | pmid = 2705657 }}</ref> They are considered to be a major source of airborne allergens.<ref name="Horner-1991">{{cite journal | vauthors = Horner WE, Lopez M, Salvaggio JE, Lehrer SB | title = Basidiomycete allergy: identification and characterization of an important allergen from Calvatia cyathiformis | journal = International Archives of Allergy and Applied Immunology | volume = 94 | issue = 1–4 | pages = 359–361 | year = 1991 | pmid = 1937899 | doi = 10.1159/000235403 }}</ref> The basidiospore family include mushrooms, [[Rust (fungus)|rusts]], [[Smut fungi|smuts]], [[Polypore|brackets]], and [[puffballs]]. 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% of those with allergic disorder, but it is believed to be less than 1% of food allergies.<ref>{{cite journal | vauthors = Sprenger JD, Altman LC, O'Neil CE, Ayars GH, Butcher BT, Lehrer SB | title = Prevalence of basidiospore allergy in the Pacific Northwest | journal = The Journal of Allergy and Clinical Immunology | volume = 82 | issue = 6 | pages = 1076–1080 | date = December 1988 | pmid = 3204251 | doi = 10.1016/0091-6749(88)90146-7 }}</ref><ref>{{cite journal | vauthors = Koivikko A, Savolainen J | title = Mushroom allergy | journal = Allergy | volume = 43 | issue = 1 | pages = 1–10 | date = January 1988 | pmid = 3278649 | doi = 10.1111/j.1398-9995.1988.tb02037.x | doi-access = free }}</ref> Heavy rainfall (which increases fungal spore release) is associated with increased hospital admissions of children with asthma.<ref>{{cite journal | vauthors = Khot A, Burn R, Evans N, Lenney W, Storr J | title = Biometeorological triggers in childhood asthma | journal = Clinical Allergy | volume = 18 | issue = 4 | pages = 351–358 | date = July 1988 | pmid = 3416418 | doi = 10.1111/j.1365-2222.1988.tb02882.x | s2cid = 27600549 }}</ref> A study in New Zealand found that 22 percent of patients with respiratory allergic disorders tested positive for basidiospores allergies.<ref name="Hasnain-1985">{{cite journal | vauthors = Hasnain SM, Wilson JD, Newhook FJ, Segedin BP | title = Allergy to basidiospores: immunologic studies | journal = The New Zealand Medical Journal | volume = 98 | issue = 779 | pages = 393–396 | date = May 1985 | pmid = 3857522 }}</ref> 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.<ref>{{cite journal | vauthors = Santilli J, Rockwell WJ, Collins RP | title = The significance of the spores of the Basidiomycetes (mushrooms and their allies) in bronchial asthma and allergic rhinitis | journal = Annals of Allergy | volume = 55 | issue = 3 | pages = 469–471 | date = September 1985 | pmid = 4037433 }}</ref> A study found that 27% of patients were allergic to basidiomycete mycelia extracts and 32% were allergic to basidiospore extracts, thus demonstrating the high incidence of fungal sensitisation in individuals with suspected allergies.<ref>{{cite journal | vauthors = Lehrer SB, Lopez M, Butcher BT, Olson J, Reed M, Salvaggio JE | title = Basidiomycete mycelia and spore-allergen extracts: skin test reactivity in adults with symptoms of respiratory allergy | journal = The Journal of Allergy and Clinical Immunology | volume = 78 | issue = 3 Pt 1 | pages = 478–485 | date = September 1986 | pmid = 3760405 | doi = 10.1016/0091-6749(86)90036-9 | doi-access = free }}</ref> It has been found that out of basidiomycete caps, mycelia, and spore extracts, the spore extracts are the most reliable extract for diagnosing basidiomycete allergy.<ref>{{cite journal | vauthors = Weissman DN, Halmepuro L, Salvaggio JE, Lehrer SB | title = Antigenic/allergenic analysis of basidiomycete cap, mycelia, and spore extracts | journal = International Archives of Allergy and Applied Immunology | volume = 84 | issue = 1 | pages = 56–61 | year = 1987 | pmid = 3623711 | doi = 10.1159/000234398 }}</ref><ref>{{cite journal | vauthors = Liengswangwong V, Salvaggio JE, Lyon FL, Lehrer SB | title = Basidiospore allergens: determination of optimal extraction methods | journal = Clinical Allergy | volume = 17 | issue = 3 | pages = 191–198 | date = May 1987 | pmid = 3608137 | doi = 10.1111/j.1365-2222.1987.tb02003.x | s2cid = 45338948 }}</ref>

In Canada, 8% of children attending allergy clinics were found to be allergic to ''[[Ganoderma]]'', a basidiospore.<ref>{{cite journal | vauthors = Tarlo SM, Bell B, Srinivasan J, Dolovich J, Hargreave FE | title = Human sensitization to Ganoderma antigen | journal = The Journal of Allergy and Clinical Immunology | volume = 64 | issue = 1 | pages = 43–49 | date = July 1979 | pmid = 447950 | doi = 10.1016/0091-6749(79)90082-4 | doi-access = free }}</ref> ''[[Pleurotus ostreatus]]'',<ref>{{cite journal | vauthors = Lopez M, Butcher BT, Salvaggio JE, Olson JA, Reed MA, McCants ML, Lehrer SB | title = Basidiomycete allergy: what is the best source of antigen? | journal = International Archives of Allergy and Applied Immunology | volume = 77 | issue = 1–2 | pages = 169–170 | year = 1985 | pmid = 4008070 | doi = 10.1159/000233775 | doi-access = free }}</ref> ''[[Cladosporium]]'',<ref>{{cite journal | vauthors = Stephen E, Raftery AE, Dowding P | title = Forecasting spore concentrations: a time series approach | journal = International Journal of Biometeorology | volume = 34 | issue = 2 | pages = 87–89 | date = August 1990 | pmid = 2228299 | doi = 10.1007/BF01093452 | s2cid = 30836940 | bibcode = 1990IJBm...34...87S }}</ref> and ''[[Calvatia cyathiformis]]'' are significant airborne spores.<ref name="Horner-1991"/> Other significant fungal allergens include ''[[Aspergillus]]'' and ''[[Alternaria]]''-''[[Penicillium]]'' families.<ref>{{cite journal | vauthors = Dhillon M | title = Current status of mold immunotherapy | journal = Annals of Allergy | volume = 66 | issue = 5 | pages = 385–392 | date = May 1991 | pmid = 2035901 }}</ref> In India, ''[[Fomes pectinatus]]'' is a predominant air-borne allergen affecting up to 22% of patients with respiratory allergies.<ref>{{cite journal | vauthors = Gupta SK, Pereira BM, Singh AB | title = Fomes pectinatis: an aeroallergen in India | journal = Asian Pacific Journal of Allergy and Immunology | volume = 17 | issue = 1 | pages = 1–7 | date = March 1999 | pmid = 10403002 }}</ref> Some fungal air-borne allergens such as ''[[Coprinus comatus]]'' are associated with worsening of [[eczema]]tous skin lesions.<ref name="Fischer-1999">{{cite journal | vauthors = Fischer B, Yawalkar N, Brander KA, Pichler WJ, Helbling A | title = Coprinus comatus (shaggy cap) is a potential source of aeroallergen that may provoke atopic dermatitis | journal = The Journal of Allergy and Clinical Immunology | volume = 104 | issue = 4 Pt 1 | pages = 836–841 | date = October 1999 | pmid = 10518829 | doi = 10.1016/S0091-6749(99)70295-2 | doi-access = free }}</ref> Children who are born during Autumn months (during fungal spore season) are more likely to develop asthmatic symptoms later in life.<ref>{{cite journal | vauthors = Harley KG, Macher JM, Lipsett M, Duramad P, Holland NT, Prager SS, Ferber J, Bradman A, Eskenazi B, Tager IB | title = Fungi and pollen exposure in the first months of life and risk of early childhood wheezing | journal = Thorax | volume = 64 | issue = 4 | pages = 353–358 | date = April 2009 | pmid = 19240083 | pmc = 3882001 | doi = 10.1136/thx.2007.090241 }}</ref>

=== Treatment ===
Treatment includes [[over-the-counter medication]]s, [[antihistamines]], [[nasal decongestants]], [[allergy shots]], and [[alternative medicine]]. In the case of nasal symptoms, antihistamines are normally the first option. They may be taken together with [[pseudoephedrine]] to help relieve a stuffy nose and they can stop the itching and sneezing. Over-the-counter options include [[clemastine]]. 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 [[dry mouth]], [[blurred vision]], [[constipation]], [[Dysuria|difficulty with urination]], confusion, and [[lightheadedness]].<ref name="PDR">{{cite web|url=http://www.pdrhealth.com/disease/disease-mono.aspx?contentFileName=BHG01AL10.xml&contentName=Seasonal+allergies&contentId=134&sectionMonograph=ht4 |title=Seasonal Allergies | work = Physician's Desk Reference |access-date=9 April 2010| archive-url= https://web.archive.org/web/20100415194735/http://www.pdrhealth.com/disease/disease-mono.aspx?contentFileName=BHG01AL10.xml&contentName=Seasonal+allergies&contentId=134&sectionMonograph=ht4| archive-date= 15 April 2010 | url-status= live}}</ref> There is also a newer second generation of antihistamines that are generally classified as [[non-sedating antihistamines]] or anti-drowsy, which include [[cetirizine]], [[loratadine]], and [[fexofenadine]].<ref name="Hay Fever Pharmacy">{{cite web |url=http://www.hayfeverpharmacy.co.nz/products/antihistamine-tablets |title=Non-Sedating or Anti-Drowsy Antihistamine Tablets | work = Hayfever Pharmacy | location = New Zealand |access-date=9 April 2010 |archive-url=https://web.archive.org/web/20100411083410/http://www.hayfeverpharmacy.co.nz/products/antihistamine-tablets |archive-date=11 April 2010 }}</ref>

An example of nasal decongestants is pseudoephedrine and its side-effects include [[insomnia]], [[anxiety (mood)|restlessness]], and difficulty urinating. Some other [[nasal spray]]s are available by prescription, including [[azelastine]] and [[ipratropium bromide]]. Some of their side-effects include drowsiness. For eye symptoms, it is important to first bathe the eyes with plain eyewash to reduce irritation. People should not wear [[contact lenses]] during episodes of [[conjunctivitis]].

[[Allergen immunotherapy]] treatment involves administering doses of allergens to accustom the body to induce specific long-term tolerance.<ref>Van Overtvelt L. et al. Immune mechanisms of allergen-specific sublingual immunotherapy. Revue française d'allergologie et d'immunologie clinique. 2006; 46: 713–720.</ref> Allergy immunotherapy can be administered orally (as [[sublingual tablets]] or sublingual drops), or by injections under the skin ([[Subcutaneous administration|subcutaneous]]).<ref>{{Cite web |date=2024-03-03 |title=Oral Immunotherapy (OIT) in Practice - FoodAllergy.org |url=https://www.foodallergy.org/resources/oral-immunotherapy-oit-practice |access-date=2024-03-03 |archive-url=https://web.archive.org/web/20240303043507/https://www.foodallergy.org/resources/oral-immunotherapy-oit-practice |archive-date=3 March 2024 }}</ref><ref>{{Cite web |title=Allergy Shots (Subcutaneous Immunotherapy) {{!}} Allergy Treatment |url=https://acaai.org/allergies/management-treatment/allergy-immunotherapy/allergy-shots/ |access-date=2024-03-03 | work = American College of Allergy, Asthma & Immunology (ACAAI) |language=en-US}}</ref> Immunotherapy contains a small amount of the substance that triggers the allergic reactions.<ref name="Mayo Clinic">{{cite web|url=http://www.mayoclinic.com/health/allergy-shots/MY01158 |title=Allergy shots | work = Mayo Clinic |access-date=9 April 2010| archive-url= https://web.archive.org/web/20100422142754/http://www.mayoclinic.com/health/allergy-shots/MY01158| archive-date= 22 April 2010 | url-status= live}}</ref>

Gradual introduction is also used for egg and milk allergies as a home-based therapy mainly for children.<ref name="Dietary Advancement Therapy Using M">{{cite journal | vauthors = Gallagher A, Cronin C, Heng TA, McKiernan A, Tobin C, Flores L, McGinley AM, Loughnane C, Velasco R, O'B Hourihane J, Trujillo J | title = Dietary Advancement Therapy Using Milk and Egg Ladders Among Children With a History of Anaphylaxis | journal = The Journal of Allergy and Clinical Immunology. In Practice | volume = 12 | issue = 8 | pages = 2135–2143 | date = August 2024 | pmid = 38729302 | doi = 10.1016/j.jaip.2024.04.057 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Chomyn A, Chan ES, Yeung J, Vander Leek TK, Williams BA, Soller L, Abrams EM, Mak R, Wong T | title = Canadian food ladders for dietary advancement in children with IgE-mediated allergy to milk and/or egg | journal = Allergy, Asthma, and Clinical Immunology | volume = 17 | issue = 1 | article-number = 83 | date = August 2021 | pmid = 34353372 | pmc = 8340453 | doi = 10.1186/s13223-021-00583-w | doi-access = free }}</ref> 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.<ref>{{cite journal | vauthors = Bloom KA, Huang FR, Bencharitiwong R, Bardina L, Ross A, Sampson HA, Nowak-Węgrzyn A | title = Effect of heat treatment on milk and egg proteins allergenicity | journal = Pediatric Allergy and Immunology | volume = 25 | issue = 8 | pages = 740–746 | date = December 2014 | pmid = 25251921 | doi = 10.1111/pai.12283 }}</ref><ref>{{cite journal | vauthors = Shin M, Han Y, Ahn K | title = The influence of the time and temperature of heat treatment on the allergenicity of egg white proteins | language = English | journal = Allergy, Asthma & Immunology Research | volume = 5 | issue = 2 | pages = 96–101 | date = March 2013 | pmid = 23450247 | pmc = 3579098 | doi = 10.4168/aair.2013.5.2.96 }}</ref><ref>{{cite journal | vauthors = Cronin C, McGinley AM, Flores L, McKiernan A, Velasco R, O'B Hourihane J, Trujillo J | title = Primary care as a setting for introducing milk using the milk ladder in children with IgE-mediated cow's milk protein allergy | journal = Clinical and Translational Allergy | volume = 13 | issue = 7 | article-number = e12286 | date = July 2023 | pmid = 37488730 | pmc = 10351366 | doi = 10.1002/clt2.12286 }}</ref> 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.<ref>{{cite journal | vauthors = Cotter S, Lad D, Byrne A, Hourihane JO | title = Home-based graded exposure to egg to treat egg allergy | journal = Clinical and Translational Allergy | volume = 11 | issue = 8 | article-number = e12068 | date = October 2021 | pmid = 34667590 | pmc = 8506942 | doi = 10.1002/clt2.12068 }}</ref><ref>{{cite journal | vauthors = Venter C, Meyer R, Ebisawa M, Athanasopoulou P, Mack DP | title = Food allergen ladders: A need for standardization | journal = Pediatric Allergy and Immunology | volume = 33 | issue = 1 | article-number = e13714 | date = January 2022 | pmid = 34882843 | doi = 10.1111/pai.13714 | veditors = Eigenmann PA }}</ref><ref name="Dietary Advancement Therapy Using M"/> The suitability of this treatment is debated between British and North American experts.<ref name="Dietary Advancement Therapy Using M"/>

== See also ==
* [[Asthma]]
* [[Asthmagen]]
* [[Bioaerosol]]
* [[Eczema]]
* [[Eggshell skull]]
* [[Hypoallergenic]]
* [[Immunodiagnostics]]
* [[List of allergies]]
* [[Nose filter]]
* [[Oral allergy syndrome]]
* [[Toxin]]

== References ==
{{reflist|30em}}

== External links ==
* {{cite web | url = http://www.hon.ch/Library/Theme/Allergy/Glossary/allergy.html | title = General information on allergy and allergens | work = Health On the Net (HON) Foundation | archive-url = https://web.archive.org/web/20170306063403/http://www.hon.ch/Library/Theme/Allergy/Glossary/allergy.html | archive-date=6 March 2017 }}
* [http://www.allermatch.org Allermatch — Sequence comparison to allergenic proteins]
* [http://fermi.utmb.edu/SDAP/ SDAP — Structural database of allergenic proteins]
* [http://www.allergome.org/script/about.php Allergome Database]
* [http://www.allergen.org Allergen Nomenclature]
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[[Category:Immune system]]
[[Category:Immunology]]
[[Category:Allergology]]