Ask Dr. Richards: 04/05

I have a friend who wants to get a cat, but shes slightly allergic. Does a longhaired cat cause a worse allergic reaction than a shorthaired cat? Or is it something besides the hair itself that causes allergies? Also, are female cats easier on allergies than male cats?

Doctors who treat human allergies routinely suggest that their cat-allergic patients not seek felines as pets – advice that often goes unheeded, as evidenced by your friend.

An even more difficult situation arises when an allergic person is advised by her physician to get rid of a cat already in the household. Wise or not, these folks may choose to get rid of the physician instead.

However, some severely allergic patients do indeed find new homes for their cats; my now-deceased Himalayan, Sherpa, found his way into my home when his former humans young child developed severe allergies. But many ailurophiles with less severe symptoms simply refuse to remove their beloved cats from their households (I know who you are). Instead, they opt to suffer the consequences.

Allergenic protein
Fel d 1, a protein produced by various parts of cats bodies – including the anal sacs, salivary glands and sebaceous glands of the skin – is the major allergen (that is, the substance capable of provoking an allergic response) that causes problems in allergic people. Fel d 1 is distributed widely on a cats body and released into the environment, often on tiny flecks of dander, where it can remain for months to years. Studies have shown that its virtually ubiquitous in indoor areas, even in homes and public places like schools, offices and public transport vehicles where cats have never been present.

Interestingly, a recent study of over 800 homes – half of which housed no cats – demonstrated allergy-provoking levels of Fel d 1 present in almost all of them. The researchers speculated that the allergen was carried into the cat-less homes on the clothing of cat-owning visitors. (Other studies have shown that clothing harbors large quantities of the Fel d 1.)

High levels of Fel d 1 are associated with increased symptoms – asthma and runny itchy eyes and nose – in allergic people. Logically, then, reducing quantities of Fel d 1 that cat-allergic people are exposed to in their homes should be helpful. Vigorous housecleaning as recommended by a physician (to remove old allergen) and not having a kitty cat (to help prevent introducing new allergen) are best. But…what if you want to get a cat?

Selecting a cat
Might it be possible to get a cat that produces less Fel d 1?

What about longhairs vs. shorthairs, or black cats vs. white? A recent study from New Zealand showed that Fel d 1 levels found in peoples living rooms were not related to either the coat color or hair length. Lesson? Dont worry about color or length of fur. 

Male vs. female? Sex hormones play a role in Fel d 1 production. Un-neutered males produce higher levels of Fel d 1 than do un-spayed females. Also, females in heat produce a lot more allergen, and males produce a lot less once theyve been neutered. Although Ive seen no studies comparing spayed females with neutered males, I suspect their allergen production is similar. Lesson? Regardless of the gender, make sure to spay or neuter.

Are there any hypoallergenic cats? Some purport that certain cat breeds (Cornish rex, Devon rex and sphynx cats in particular) are inherently less allergenic than others, but Ive seen no data to support the claims. Lesson? Buyer beware. (As an aside, some researchers are trying to genetically engineer cats that dont make Fel d 1.  Ethical considerations aside, no one knows yet if this is possible.)

Having said this, though, some people swear that their allergic symptoms are less severe with certain cats than with others, so its possible that a specific cat (or breed?) may be less allergenic to a specific allergic person. Ive seen no studies to support this and I admit my skepticism. If this is true, it may be wise for an allergic person to cautiously spend some time with several potential feline housemates before adoption, just to see if one provokes milder symptoms.