Causes
By Mayo Clinic staffDuring a process called sensitization, your immune system mistakenly identifies a harmless airborne substance as something harmful. Your immune system then starts producing antibodies to this harmless substance. The next time you come in contact with the substance, these antibodies recognize it and signal your immune system to release chemicals such as histamine into your bloodstream. These immune system chemicals cause a reaction that leads to the irritating signs and symptoms of hay fever.
Seasonal hay fever triggers include:
- Tree pollen, common in the spring
- Grass pollen, common in the late spring and summer
- Weed pollen, common in the fall
- Spores from fungi and molds, which can be worse during warm-weather months
Year-round hay fever triggers include:
- Dust mites or cockroaches
- Dander (dried skin flakes and saliva) from pets such as cats, dogs or birds
- Spores from indoor and outdoor fungi and molds
Hay fever doesn't mean you're allergic to hay. Despite its name, hay fever is almost never triggered by hay, and it doesn't cause a fever.
- Weber RW. Allergic rhinitis. Primary Care Clinics in Office Practice. 2008;35:1.
- Eapen RJ, et al. Allergic rhinitis — History and presentation. Otolaryngology Clinics of North America. 2008;41:325.
- deShazo RD, et al. Patient information: Allergic rhinitis (seasonal allergies). http://www.uptodate.com/home/index.html. Accessed Feb. 19, 2010.
- Practice parameters for managing allergic rhinitis. American Family Physician. http://www.aafp.org/afp/2009/0701/p79.html. Accessed Feb. 25, 2010.
- deShazo RD, et al. Pharmacotherapy of allergic rhinitis. http://www.uptodate.com/home/index.html. Accessed Feb. 19, 2010.
- Rabago D, et al. Saline nasal irrigation for upper respiratory conditions. American Family Physician. 2009;80:1117.
- Tips to remember: Indoor allergens. American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/publicedmat/tips/indoorallergens.stm. Accessed Feb. 19, 2010.
- Tips to remember: Outdoor allergens. American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/publicedmat/tips/outdoorallergens.stm. Accessed Feb. 19, 2010.
- Herbs and other dietary supplements. In: Bauer B. Mayo Clinic Book of Alternative Medicine. 2nd ed. New York, N.Y.: Time Inc.; 2010:173.
- Man L. Complementary and alternative medicine for allergic rhinitis. Current Opinion in Otolaryngology & Head and Neck Surgery. 2009;17:226.
- Naegleria FAQs. Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/naegleria/faqs.html. Accessed Dec. 30, 2011.

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