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Owning a Cat in Childhood May Lower Adult Allergies

From the WebMD Archives

Dec. 6, 1999 (Atlanta) -- A dog is man's best friend, but for infants, it may be a cat.

A new study published in the November issue of The Journal of Allergy and Clinical Immunology shows that exposure to "furred" pets, particularly cats, during childhood may help ward off allergic sensitivities to the animals as an adult, and perhaps to other respiratory ailments as well. Unfortunately, the same doesn't hold true if one decides to start owning a pet later in life.

Researchers from Switzerland and the United Kingdom joined forces to compile data from more than 13,000 people in 16 countries. They were all blood tested for antibodies to cat allergens, which would show an allergic sensitivity to cats. The researchers also determined who among those people actually developed allergic symptoms, or who had other respiratory conditions such as asthma.

"There is evidence that if you have animals, cats and dogs, in childhood, also during pregnancy, this will have an influence on the immune system, the developing immune system of the infant," Hans-Peter Roost, PhD, the study's lead author, tells WebMD.

Roost says his study did not include information about whether pets were kept during pregnancy, and "clearly it is not advisable to start the keeping of pets, such as cats, during pregnancy because of the risks," such as toxoplasmosis, an infection that can lead to birth defects and that is potentially brought on by contact with certain animals. He also says people who know they're allergic to cats should avoid them.

But ownership of a cat before becoming pregnant may induce some immunity in the mother, which could then protect the infant, according to Roost, who is an immunologist with the federal office of public health in Switzerland. He says the topic of pregnancy requires further study.

The relationship between cats and asthma also requires further study, says Roost. He and his colleagues write, "The current study focuses on sensitization to cat which was shown [in a previous study] to be an important risk factor for the development of asthma."

Roost tells WebMD, "About 70% of asthmatics have one or more sensitivities to multiple kinds of allergens; it [cats] is really a strong risk factor. It doesn't explain the disease completely, but it's really a risk factor for asthma as well."

The study counters some earlier suggestions, Roost and colleagues write, that cat ownership as a child would increase that person's risk of being extra-sensitive to the animals as an adult. "The whole story goes like this," Roost tells WebMD. "It goes to the direction of antigenic stimulation. Today we are living in a society where the hygiene has taken over, but actually the immune system needs a certain microbiological stimulation to develop. So it has probably gone a little too much in the other direction, too much hygiene, and what we find in a newer study ... that is if children grow up on a farm they have a very strong effect of being protected from allergies and asthma. If you live on a farm, you have multiple animal contacts and you have a lot of bacteria around, and this obviously has a beneficial effect in regard to allergy and asthma."

Roost says his study shows "it's a different story" for people who decide to begin keeping cats as adults. For them, the researchers say, "Results demonstrate a significant risk of [developing] sensitization to cats when they are allowed indoors." If cats are kept outdoors, the risk decreases greatly ... for the owner.

Cats, as domestic animals go, induce allergic symptoms far more frequently than other animals, for two main reasons. They tend to invade the home space more completely, and they groom by licking, so their shed skin, or allergy-inducing "dander," has saliva added into the mix. Saliva is full of allergens.

So where does that leave people who either love or loathe cats? Somewhere in the middle: Cats can cause allergies to people inside and outside of the home, but being around a feline as an infant may lead to less itching and sniffing as an adult, according to the study.

Elaine Gonsior, MD, an allergist with Kansas State University, did not mince words in an interview with WebMD seeking objective commentary. She says, "Basically, what it sounds like ... they did the study so people could just justify having pets. So it sounds to me like [if] you have a family with six to eight kids in the family, between the family size and the facts that the kids were exposed to cats, those kids should be scot-free [from risk of allergies] when they're 25 or 35. But I don't think it works that way."

Vital Information:

  • Owning a cat can cause allergies in adults, but infants who are exposed to the animals are less likely to develop allergies to them later in life.
  • The developing immune system needs a certain amount of microbiological stimulation, such as contact with bacteria, which it may not be getting in today's hygiene-conscious society.
  • This study did not look at the effects of pet ownership during pregnancy, but this would not be encouraged in anyone because of the associated risks.