As he puts it, "Previously we had thought that being exposed to those things that you are allergic to, or being exposed to things that make you allergic, make your more likely to become asthmatic. But what this sort of demonstrated was that maybe very high levels of exposure, or something else associated with being exposed to a cat would make you less likely to develop asthma." Perzanowski was determined to see if these results could be replicated in the United States.
As they wrote in the Journal of Allergy and Clinical Immunology, Perzanowski and colleagues at Columbia University's Mailman School of Public Health studied a group of children living in New York City, measuring allergen levels in each home and comparing it with kids' allergy and asthma history. They found that by age five, kids who grew up around high levels of cat allergens were far less likely to show allergy or asthma symptoms.
But what is causing the protective effect in the first place? Perzanowski doesn't have any definitive answers yet, but he believes the key lies in the sheer volume of allergen exposure that living with a cat leads to. He says that, "People with cats at home are exposed to especially high levels of cat allergen, probably to the order of a hundred times greater than homes without cats. And maybe that higher level of exposure is what's causing this protective effect." This theory is similar to the "Hygiene Hypothesis", which proposes that exposure to bacteria and viral agents can actually be beneficial, since it gives the immune system an opportunity to respond to these pathogens, and therefore build up immunities. But more research is needed before scientists can pin down what is behind this effect.
And what does all this mean for cat owners who are worried about their children developing asthma? Perzanowski says that "we don't need to avoid pets to prevent asthma… at least, before the asthma has set… before symptoms have developed." Meaning that unless your child already shows signs of an allergic response or asthmatic symptoms around cats, there's no need to second-guess the decision to buy them a feline companion.
However, Perzanowski warns that buying a cat won't necessarily help your kids, and if they already have asthma, cats are something to avoid. The protective effect was only shown in children who had lived with a cat from birth to age five, and there is currently no data to indicate whether the effect continues past those early years of exposure. But if you own a cat and have a baby on the way, it's possible that your pet could keep your child asthma free.
This research was published in the April 2008 issue of the Journal of Allergy and Clinical Immunology, and was funded by the National Institute of Environmental Health Sciences and the U.S. Environmental Protection Agency.