Most humans mount significant Immunoglobulin E (IgE) responses only as a defense against parasitic infections. However, some individuals mount an IgE response against common environmental antigens. This hereditory predisposition is called atopy. In atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity. Sensitivities vary from one person to another and it is possible to be allergic to an extraordinary range of substances.
Types of allergies
Dust mite excretion, pollen and pet dander are all common allergens, but it is possible to be allergic to anything from chlorine to perfume to royal jelly. Food allergies are not as common as food sensitivity, but some foods such as peanuts (a legume), nuts, seafood and shellfish are the cause of serious allergies in many people.
Officially, the Food and Drug Administration does recognize eight foods as being common for allergic reactions in a large segment of the sensitive population, which includes peanuts, tree nuts, eggs, milk, shellfish, fish, wheat and their derivatives, soy and their derivatives, and sulfites (chemical based, often found in flavors and colors in foods) at 10ppm and over. See the FDA website for complete details. It should be noted that other countries, due to differences in the genetic profiles of its citizens and different levels of exposure to different foods, the "official" allergen list will change. Canada recognizes all eight of the allergens recognized by the US, and also recognizes sesame seeds.
A few people have been recorded to be allergic to certain chemicals found in almost all water, and even water itself (see Aquagenic pruritus).
Another type of allergen is urushiol, a resin produced by poison ivy and poison oak. It 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. A little over half of North Americans are known to be allergic to urushiol and repeated exposure can increase one's sensitivity to the allergen.
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, generally resulting in hives). Other common causes of serious allergy are wasp, fire ant and bee stings, penicillin, and latex. An extremely serious form of an allergic reaction is called anaphylaxis. 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.
In 1952 basidiospores were described as being possible airborne allergens and were linked to asthma in 1969. Basidiospore are the dominant airborne fungal allergens. Fungal allergy is associated with seasonal asthma. They are considered to be a major source of airborne allergens. The basidospore family include mushrooms, rusts, smuts, 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 percent of those with allergic disorder, but it is believed to be less than 1 percent of food allergies. Heavy rainfall (which increases fungal spore release) is associated with increased hospital admissions of children with asthma. A study in New Zealand found that 22 percent of patients with respiratory allergic disorders tested positive for basidiospores allergies. 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. 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. It has been found that of basidiomycete cap, mycelia, and spore extracts that spore extracts are the most reliable extract for diagnosing basidiomycete allergy.
In Canada, 8% of children attending allergy clinics were found to be allergic to Ganoderma which is a basidiospore. Pleurotus ostreatus, cladosporium, and calvatia cyathiformis are significant airborne spores. Other significant fungal allergens include aspergillus and alternaria-penicillin families. In India fomes pectinatis is a predominant air bourne allergen effecting up to 22 percent of patients with respiratory allergies. Some fungal air-bourne allergens such as coprinus comatus are associated with worsening of eczematous skin lesions. Children who are born during autumn months (during fungal spore season) are more likely to develop asthmatic symptoms later in life.
In addition to foreign proteins found in foreign serum (from blood transfusions) and vaccines, common allergens include:
- Animal products
- Fel d 1 (cat allergy)
- and dander
- cockroach calyx
- dust mite excretion
- salicylates (also found naturally in numerous fruits)
- local anaesthetics
- celery and celeriac 
- corn or maize
- eggs (typically albumen, the white)
- tree nuts
- tree nuts
- Insect stings
- bee sting venom
- wasp sting venom
- mosquito stings
- Mold spores
- Plant pollens (hay fever)
- grass — ryegrass, timothy-grass
- weeds — ragweed, plantago, nettle, artemisia vulgaris, chenopodium album, sorrel
- trees — birch, alder, hazel, hornbeam, aesculus, willow, poplar, platanus, tilia, olea, Ashe juniper
Seasonal allergy symptoms are commonly experienced part 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 Bermuda, 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 include rhinitis, which causes sneezing and a runny nose, as well as allergic conjunctivitis, which includes watering and itchy eyes. 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. Moreover, since the sinuses may also become congested, some people experience headaches.
Treatment includes over-the-counter medications, 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. Some over-the-counter options are Benadryl and Tavist. 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, difficulty with urination, confusion, and light-headedness.
There is also a newer second generation of antihistamines which are generally classified as the "non-sedating antihistamines" or anti-drowsy which include cetirizine, loratadine, and fexofenadine.
An example of nasal decongestants is pseudoephedrine and its side effects include insomnia, restlessness, and difficulty urinating. Some other nasal sprays are available by prescription, and they include: Azelastine, and Ipratropium. 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 wear contact lenses during episodes of conjunctivitis.
Allergy shots, also called immunotherapy, are also available and are especially recommended for people who cannot tolerate allergy medications or who experience severe symptoms, and also for those who develop asthma during pollen season.
Immunotherapy contains a small amount of the substance that triggers the allergic reactions  and it should start after the pollen season to get prepared for the next season.
- Eggshell skull
- Nose filter
- ↑ Goldsby, Richard A. et al.,Immunology. 5th ed. New York: W.H. Freeman and Company, 2000.
- ↑ Rosmilah, M; et al. (December 2008). "Characterization of major allergens of royal jelly Apis mellifera". Trop Biomed 25 (3): 243–51. PMID 19287364.
- ↑ "Health Canada: Food Allergies". http://www.hc-sc.gc.ca/fn-an/securit/allerg/index_e.html. Retrieved 2007-06-09.
- ↑ GREGORY, PH.; HIRST, JM. (Sep 1952). "Possible role of basidiospores as air-borne allergens.". Nature 170 (4323): 414. doi:10.1038/170414a0. PMID 12993181.
- ↑ Herxheimer, H.; Hyde, HA.; Williams, DA. (Jul 1969). "Allergic asthma caused by basidiospores.". Lancet 2 (7612): 131–3. PMID 4183245.
- ↑ Hasnain, SM.; Wilson, JD.; Newhook, FJ. (May 1985). "Fungal allergy and respiratory disease.". N Z Med J 98 (778): 342–6. PMID 3858721.
- ↑ Levetin, E. (Apr 1989). "Basidiospore identification.". Ann Allergy 62 (4): 306–10. PMID 2705657.
- ↑ 8.0 8.1 Horner, WE.; Lopez, M.; Salvaggio, JE.; Lehrer, SB. (1991). "Basidiomycete allergy: identification and characterization of an important allergen from Calvatia cyathiformis.". Int Arch Allergy Appl Immunol 94 (1-4): 359–61. doi:10.1159/000235403. PMID 1937899.
- ↑ Sprenger, JD.; Altman, LC.; O'Neil, CE.; Ayars, GH.; Butcher, BT.; Lehrer, SB. (Dec 1988). "Prevalence of basidiospore allergy in the Pacific Northwest.". J Allergy Clin Immunol 82 (6): 1076–80. doi:10.1016/0091-6749(88)90146-7. PMID 3204251.
- ↑ Koivikko, A.; Savolainen, J. (Jan 1988). "Mushroom allergy.". Allergy 43 (1): 1–10. doi:10.1111/j.1398-9995.1988.tb02037.x. PMID 3278649.
- ↑ Khot, A.; Burn, R.; Evans, N.; Lenney, W.; Storr, J. (Jul 1988). "Biometeorological triggers in childhood asthma.". Clin Allergy 18 (4): 351–8. doi:10.1111/j.1365-2222.1988.tb02882.x. PMID 3416418.
- ↑ Hasnain, SM.; Wilson, JD.; Newhook, FJ.; Segedin, BP. (May 1985). "Allergy to basidiospores: immunologic studies.". N Z Med J 98 (779): 393–6. PMID 3857522.
- ↑ Santilli, J.; Rockwell, WJ.; Collins, RP. (Sep 1985). "The significance of the spores of the Basidiomycetes (mushrooms and their allies) in bronchial asthma and allergic rhinitis.". Ann Allergy 55 (3): 469–71. PMID 4037433.
- ↑ Lehrer, SB.; Lopez, M.; Butcher, BT.; Olson, J.; Reed, M.; Salvaggio, JE. (Sep 1986). "Basidiomycete mycelia and spore-allergen extracts: skin test reactivity in adults with symptoms of respiratory allergy.". J Allergy Clin Immunol 78 (3 Pt 1): 478–85. doi:10.1016/0091-6749(86)90036-9. PMID 3760405.
- ↑ Weissman, DN.; Halmepuro, L.; Salvaggio, JE.; Lehrer, SB. (1987). "Antigenic/allergenic analysis of basidiomycete cap, mycelia, and spore extracts.". Int Arch Allergy Appl Immunol 84 (1): 56–61. doi:10.1159/000234398. PMID 3623711.
- ↑ Liengswangwong, V.; Salvaggio, JE.; Lyon, FL.; Lehrer, SB. (May 1987). "Basidiospore allergens: determination of optimal extraction methods.". Clin Allergy 17 (3): 191–8. doi:10.1111/j.1365-2222.1987.tb02003.x. PMID 3608137.
- ↑ Tarlo, SM.; Bell, B.; Srinivasan, J.; Dolovich, J.; Hargreave, FE. (Jul 1979). "Human sensitization to Ganoderma antigen.". J Allergy Clin Immunol 64 (1): 43–9. doi:10.1016/0091-6749(79)90082-4. PMID 447950.
- ↑ Lopez, M.; Butcher, BT.; Salvaggio, JE.; Olson, JA.; Reed, MA.; McCants, ML.; Lehrer, SB. (1985). "Basidiomycete allergy: what is the best source of antigen?". Int Arch Allergy Appl Immunol 77 (1-2): 169–70. doi:10.1159/000233775. PMID 4008070.
- ↑ Stephen, E.; Raftery, AE.; Dowding, P. (Aug 1990). "Forecasting spore concentrations: a time series approach.". Int J Biometeorol 34 (2): 87–9. doi:10.1007/BF01093452. PMID 2228299.
- ↑ Dhillon, M. (May 1991). "Current status of mold immunotherapy.". Ann Allergy 66 (5): 385–92. PMID 2035901.
- ↑ Gupta, SK.; Pereira, BM.; Singh, AB. (Mar 1999). "Fomes pectinatis: an aeroallergen in India.". Asian Pac J Allergy Immunol 17 (1): 1–7. PMID 10403002.
- ↑ Fischer, B.; Yawalkar, N.; Brander, KA.; Pichler, WJ.; Helbling, A. (Oct 1999). "Coprinus comatus (shaggy cap) is a potential source of aeroallergen that may provoke atopic dermatitis.". J Allergy Clin Immunol 104 (4 Pt 1): 836–41. doi:10.1016/S0091-6749(99)70295-2. PMID 10518829.
- ↑ Harley, KG.; Macher, JM.; Lipsett, M.; Duramad, P.; Holland, NT.; Prager, SS.; Ferber, J.; Bradman, A. et al. (Apr 2009). "Fungi and pollen exposure in the first months of life and risk of early childhood wheezing.". Thorax 64 (4): 353–8. doi:10.1136/thx.2007.090241. PMID 19240083.
- ↑ Bublin M; Radauer C; Wilson IBH; Kraft D; Scheiner O; Breiteneder H; Hoffmann-Sommergruber K (2003). "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". FASEB 17 (12): 1697–1699. doi:10.1096/fj.02-0872fje. PMID 12958180. http://www.fasebj.org/cgi/content/full/17/12/1697
- ↑ "Seasonal Allergy - What to Know". http://seasonalallergies.us/. Retrieved 2010-04-09.
- ↑ "Seasonal Allergies". http://www.merck.com/mmhe/sec16/ch185/ch185b.html. Retrieved 2010-04-09.
- ↑ "Seasonal Allergies". http://www.pdrhealth.com/disease/disease-mono.aspx?contentFileName=BHG01AL10.xml&contentName=Seasonal+allergies&contentId=134§ionMonograph=ht4. Retrieved 2010-04-09.
- ↑ "Non-Sedating or Anti-Drowsy Antihistamine Tablets". http://www.hayfeverpharmacy.co.nz/products/antihistamine-tablets. Retrieved 2010-04-09.
- ↑ "Allergy shots". http://www.mayoclinic.com/health/allergy-shots/MY01158. Retrieved 2010-04-09.