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Growing up with pets helps reduce allergies

Dog? Cat? Why not both? A study published in the Journal of Allergy and Clinical Immunology found that a reduced risk of developing allergies occurred in those individuals that had both cats and dogs growing up.

For the study, the researchers looked at survey responses from parents of over 1000 children born in 1972 to 1973 from New Zealand. If the children were reported as having had a cat or dog in the home at nine years old or less, then they were considered in the group of having lived with animals in childhood. Children were first assessed at three years of age and again at five, seven, nine, 11, 13, 15, 18, 21, 26, and 32 years old. Skin prick tests were done at thirteen and thirty-two years old to test for possible allergies. The skin test was chosen to be done at 13 years of age because that is when most children report developing symptoms of nasal allergies. The allergens tested for included dog, cat, and horse hair, as well as other common nasal allergens such as dust mites, grass, and wool.

Both are better than one

A reduced risk of developing allergies at age 13 years was seen in children who had both a cat and a dog at home by nine years of age. Interestingly, the researchers found that the combination of both cat and dog, or even multiple animals, is more helpful in reducing allergies than exposure to just a cat or dog alone. Almost 50% (49.4%) of children who had neither a cat or dog before age nine had allergies to what was tested for, whereas only 37% of children who had both dogs and cats growing up had allergies. These findings stayed true even at the followup at age 32; those who had both cats and dogs suffered from allergies less.

It is important to note that according to the survey results, having a history of allergies in the family did not affect the possibility of parents having pets in the house while their children were young. For example, parents with a history of asthma or hay fever were no less likely to have cats or dogs in the house at the time of the child’s birth and were no more or less likely to acquire or get rid of a cat or dog in the first 9 years of the child’s life.

Possible reasons why pets protect children from allergies

Although it still isn’t clear why the combination of both dogs and cats helps protect against allergies, the researchers give possible explanations that they hope can be further explored in future studies. One explanation may be that children exposed to both cats and dogs are likewise exposed to two different types of allergens, since dogs and cats carry different biochemical characteristics. More exposure to various allergens could mean increased tolerance for a greater variety of allergens. Furthermore, living with animals also increases exposure to various forms of bacteria. Thus, it is possible that having both animals results in a wider range of exposure to bacteria, strengthening the child’s immune system.

These suggestions are strengthened by other studies that have found that children, who, for example, had more exposure to other children due to day care attendance or siblings, had lower risks of nasal allergies. The same was found for children growing up on a farm, supporting the hypothesis that more exposure to various bacteria early on may help build up a tolerance for allergens.

Maybe it's time to consider introducing some new furry family members into the home.

For more information about allergies, take a look at the following pages:

 Ali Elliott
Editorial Intern, AboutKidsHealth

7/26/2011

Mandane P, Sears M, Poulton R, et al. "Cats and Dogs and the Risk of Atopy in Childhood and Adulthood". Journal of Allergy and Clinical Immunology. 2009;124:745-50

Matheson M, Dharmage S, Abramson M, et al. "Early-life risk factors and incidence of rhinitis: Results from the European Community Respiratory Health Study - an international population-based cohort study". Journal of Allergy and Clinical Immunology. 2011





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