Cat allergy is the most common animal allergy and is a strong risk factor for asthma.   In fact, cat allergy was found to account for almost a third of all asthma
cases in a 2007 study performed by the National Institute of Health.    

What causes cat allergy?
A common misconception is that cat allergic individuals are allergic to cat hair and long haired cats are more allergenic than short haired cats.    However,  
this is no the case.    Cat allergy does not come from the hair itself, but from proteins that stick on the hair.   The hair particles then become airborne and are
subsequently inhaled into the nose and lungs, resulting in allergy symptoms.

The major cat allergen is a tiny protein found in saliva and sweat called Fel d 1.    Another important cat allergen is cat albumin (called Fel d 2) which is found
in cat urine and skin dander.   As the cat grooms itself, it will spread the allergens over its fur by licking itself.   All cats produce allergens, although some cats
produce more than others.    Overall, male cats produce more allergens than female cats, but the difference is not significant enough to make a difference for
individuals allergic to cats.   

Cat allergens are transferred from place to place by floating in the air and by sticking on clothing and hair, making them detectable in locations where cats are
not normally found, such as shopping malls, movie theaters, hotels, and doctor offices, so it is nearly impossible to avoid cat allergen exposure.   In fact,
several studies showed that:
  • 56% of homes that never had cats contained levels of cat allergens high enough to sensitize people to cat allergy.
  • 16% of homes that never had cats contained levels of cat allergens high enough to cause asthma symptoms.
  • Within 3 weeks, new mattresses in stores had the same level of cat allergens as those in houses where cats used to live.
  • It may take up to 6 months after removal of a cat for the bulk of cat allergens to disappear from the home.
  • It can take up to 5 years for cat allergens in mattresses to decrease to levels found in homes without cats.

How to minimize cat allergens in the home
Removing the cat from the house is the best way to improve cat allergies.   Keeping the cat out of the bedroom is not very effective since cat allergen is
transferred from room to room by the owner’s clothing.   Remember that it can take a good 6 months before the cat allergen levels are low enough that they
will not longer be a problem.

If removing the cat from the house is not possible, some studies demonstrate that doing all the following measures
together may help
  • Minimize carpeting.    Go for linoleum, tile, or hardwood floors.
  • Minimize upholstered furniture.  Go for leather furniture.
  • Vacuum floors, carpets, and furniture weekly.   Make sure the vacuum has a HEPA filter.
  • Wet mop floors weekly
  • Wipe walls and furniture weekly.   Dust cleaners such as the Swiffer® and Grab-It™ dust cloths work quite well.
  • Wash the cat at least weekly – this will help decrease the allergens on the skin and hair.  
  • Wash bedding at 130˚ F (60˚ C) weekly
  • Keep the cat out of all bedrooms
  • Close closets at all times when not in use

Diagnosis of Cat allergy
Cat allergy is diagnosed with a skin or blood test.

Treatment of cat allergy
Along with avoidance, medications such as antihistamines (Benadryl, Allegra, Claritin, Zyrtec,…) and steroid nose sprays (Flonase, Nasonex, Rhinocort,…)
can help minimize allergy symptoms.    
Allergy shots (immunotherapy) has been demonstrated to be effective for the long term treatment of cat allergies.   


updated 20 April 2010

Sources:
Arbes S et al.  Asthma cases attributable to atopy: Results from the Third National Health and Nutrition Examination Survey  
J Allergy Clin Immunol 207;
120:1139-45.
Custovic A et al. Controlling indoor allergens
Ann Allergy Asthma Immunol 2002;88:432-442.
Björnsdottir US et al. The Effect of reducing levels of cat allergen (Fel d 1) on clinical symptoms in patients with cat allergy.
Ann Allergy Asthma Immunol
2003:91:189-194.
Egmar AC et al. Deposition of cat, dog, and horse allergen over time in public environments-a model of dispersion.  
Allergy 1998;53:957-961.
Wood RA et al. The effect of cat removal on allergen content in the household dust samples.
J Allergy Clin Immunol 1989;83:730-734.
Allergen immunotherapy: A practice parameter second update  
J Allergy Clin Immunol 2007;120:s26-s85

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Cat Allergy