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Causes

By Mayo Clinic staff

Allergies occur when your immune system reacts to a foreign substance such as pollen, bee venom or pet dander.

Your immune system produces proteins known as antibodies. These antibodies protect you from unwanted invaders that could make you sick or cause an infection. When you have allergies, your immune system makes antibodies that identify your particular allergen as something harmful, even though it isn't. When you inhale the allergen or come into contact with it, your immune system responds and produces an inflammatory response in your nasal passages or lungs. Prolonged or regular exposure to the allergen can cause the ongoing (chronic) inflammation associated with asthma.

Cats and dogs
Allergens from cats and dogs are found in skin cells the animals shed (dander), in saliva and on hairs. Dander is a particular problem because it is very small and can remain airborne for long periods of time with the slightest bit of air circulation. It also collects easily in upholstered furniture and sticks to your clothes.

Pet saliva can stick to carpets, bedding, furniture and clothing. Dried saliva can become airborne.

A so-called hypoallergenic dog may shed less fur than a shedding dog, but no dog breed is truly hypoallergenic.

Rodents and rabbits
Rodent pets include mice, gerbils, hamsters and guinea pigs. Allergens from rodents are usually present in hair, dander, saliva and urine. Dust from litter or sawdust in the bottom of cages may contribute to airborne allergens from rodents.

Rabbit allergens are present in dander, hair and saliva.

Other pets
Pet allergy is rarely caused by animals that don't have fur, such as fish and reptiles.

Risk factors Symptoms
References
  1. Platts-Mills, TAE. Indoor allergens. In: Adkinson NF, et al. Middleton's Allergy: Principles and Practice. 7th ed. St. Louis, Mo.: Mosby; 2008. http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-0-323-05659-5..00033-4--cesec40&isbn=978-0-323-05659-5&sid=1049616576&type=bookPage&sectionEid=4-u1.0-B978-0-323-05659-5..00033-4--cesec41&uniqId=217729073-3#4-u1.0-B978-0-323-05659-5..00033-4--cesec41. Accessed Sept. 8, 2010.
  2. Atkins D, et al. Diagnosis of allergic disease. In: Kliegman RM, et al. Nelson Textbook of Pediatrics, 18th ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/das/book/body/217729073-4/1049619087/1608/434.html#4-u1.0-B978-1-4160-2450-7..50142-0--cesec3_3369. Accessed Sept. 8, 2010.
  3. Balkissoon RC, et al. Disorders of the upper airways. In: Mason RJ, et al. Murray & Nadel's Textbook of Respiratory Medicine, 5th ed. Philadelphia, Pa.: Saunders Elsevier; 2010. http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-1-4160-4710-0..00043-2--s0015&isbn=978-1-4160-4710-0&sid=1049622658&type=bookPage&sectionEid=4-u1.0-B978-1-4160-4710-0..00043-2--s0055&uniqId=217729073-5#4-u1.0-B978-1-4160-4710-0..00043-2--s0055. Accessed Sept. 8, 2010.
  4. DeShazo RD, et al. Diagnosis of allergic rhinitis (rhinosinusitis). http://www.uptodate.com/home/index.html. Accessed Sept. 8, 2010.
  5. DeShazo RD, et al. Clinical manifestations and epidemiology of allergic rhinitis (rhinosinusitis). http://www.uptodate.com/home/index.html. Accessed Sept. 8, 2010.
  6. DeShazo RD, et al. Pharmacotherapy of allergic rhinitis. http://www.uptodate.com/home/index.html. Accessed Sept. 8, 2010.
  7. Managing indoor allergen culprits. American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/elements/2009/12/1209_elements.pdf. Accessed Sept. 8, 2010.
  8. Battling pet allergies. American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/just4kids/pet_allergies.asp. Accessed Sept. 8, 2010.
  9. Ferguson BJ. Environmental controls of allergies. Otolaryngologic Clinics of North America. 2008;41:411.
  10. Tips to remember: Allergy testing. American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/publicedmat/tips/whatisallergytesting.stm. Accessed Sept. 8, 2010.
  11. Tips to remember: Allergy shots. American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/publicedmat/tips/whatareallergyshots.stm. Accessed Sept. 8, 2010.
  12. Wegienka GR, et al. Pet ownership is good for the soul, but is it good for the immune system? American Academy of Allergy, Asthma & Immunology. http://www.aaaai.org/patients/jaci/content.asp?contentid=9995. Accessed Sept. 8, 2010.
  13. Pet allergy. American College of Allergy, Asthma & Immunology. http://www.acaai.org/patients/resources/allergies/Pages/pet-allergy.aspx. Accessed Sept. 8, 2010.
  14. Pet allergies. Asthma and Allergy Foundation of America. http://www.aafa.org/display.cfm?id=8&sub=16&cont=63. Accessed Sept. 15, 2010.
  15. Li JT (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 16, 2010.
DS00859 Nov. 17, 2010

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