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April 7, 2013

Cats, Kids & Asthma

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Mother to Child Immunity


Centers for Disease Control and Prevention - Asthma

Mailman School of Public Health

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Are cats good at preventing asthma? That's the finding of a group of scientists studying childhood allergies in houses with and without cats, as this ScienCentral video reports.

[If you cannot see the youtube video below, you can click here for a high quality mp4 video.]

Interviewee: Matt Perzanowski,
Mailman School of Public Health
Length: 1 min 33sec
Produced by Chris Bergendorff
Edited by Chris Bergendorff
Copyright © ScienCentral, Inc.

Feline Protection

Cats may be affectionate pets, but, for many of us, cat dander causes trouble—of the sneezy, wheezy kind. Being around cats can spark allergy attacks, and even lead to the development of asthmatic symptoms.

Now, Allergy Researcher Matt Perzanowski has good news: Cats may actually be protecting some kids from getting sick. This paradoxical finding means that while cat allergy and asthma often go hand in hand, in some cases allergen exposure over a long period of time at a young age can actually prevent or shield against asthma symptoms. "Being allergic to a cat was a strong risk factor for having asthma. Children who grew up with a cat are less likely to develop asthma," Perzanowski says.

Perzanowski discovered this result as part of his research into the swiftly rising number of asthma cases across the globe. The disease has reached epidemic proportions in the U.S., and is especially prevalent in low-income urban neighborhoods. Perzanowski says that kids living in these crowded inner city areas are most at risk. "Asthma prevalence is now between one in four and one in three kids, so a really large percentage of kids develop asthma and asthma symptoms early in life."

Perzanowski is just one of many researchers all over the world who are dedicated to getting to the bottom of this looming health crisis. Some are focusing on other populations that show a resistance to asthma, like children growing up on farms. Other researchers are looking at the many various sources of allergens that could be behind rising asthma cases, like dust mites and cockroaches.

Perzanowski decided to investigate the possible protective effect of cat allergen exposure after working on a similar study in Sweden six years ago. That study was one of the first to show that owning a cat could possibly be giving children a small protective effect against asthma. These findings encouraged Perzanowski to continue to investigate the issue when he returned to do research in the United States. He was especially intrigued by how these findings seemed to challenge the established wisdom of allergen exposure and development of asthma.

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.

       email to a friend by Christopher Bergendorff

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