(Medical Xpress) -- According to a new study published in The Journal of Allergy and Clinical Immunology, getting a cat for the first time as an adult can nearly double your chances of developing allergies to the cat dander.

The new study, led by Dr. Mario Olivieri from the University Hospital of Verona in Italy, looked at 6,000 adult Europeans over the course of nine years. At the beginning of the study, all participants received blood tests to look for sensitivity to animal dander. None of the participants had this sensitivity at the beginning of the study.

Over the course of nine years, about three percent of the participants that did not have a cat developed sensitivity to dander. Of those that did acquire a cat, five percent developed an allergy.

Of those that developed a sensitivity, four out of 10 also experienced allergy symptoms such as wheezing, itchy eyes and sneezing.

The study also looked at adults who had cats as children. The results showed that these individuals had a much smaller risk of developing sensitivity. Getting a cat as a child can prove to be protective against developing allergies later in adulthood.

However, the interesting part of this study revealed that where your cat lives and spends his time can also make a difference in the development of an allergy. Those cat owners who did not allow their cats into their bedroom did not become sensitized at all.

The researchers recommend that if you have a cat, keep him out of your bedroom and consider a HEPA filter to reduce the amount of dander in the environment. If you become allergic, they advise finding a new home for the pet. If this is not an option, there are medical treatments such as shots or immunotherapy.

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More information: Risk factors for new-onset cat sensitization among adults: A population-based international cohort study, The Journal of Allergy and Clinical Immunology, Article in Press, Risk factors for new-onset cat sensitization among adults: A population-based international cohort study,, Article in Press, www.jacionline.org/article/S0091-6749 %2811%2901741-6/abstract Abstract

Background. Cat exposure during childhood has been shown to increase the risk of developing cat sensitization, while the effect of cat exposure in adulthood has not yet been established.

Objective. To evaluate new-onset sensitization to cat in adulthood in relation to changes in cat keeping.

Methods. A total of 6292 European Community Respiratory Health Survey I (ECRHS I) participants aged 20 to 44 years from 28 European centers, who were not sensitized to cat, were reevaluated 9 years later in ECRHS II. Present and past cat ownership and total and specific IgE levels were assessed in both surveys. Allergen-specific sensitization was defined as a specific serum IgE level of 0.35 kU/L or more.

Results. A total of 4468 subjects did not have a cat in ECRHS I or ECRHS II, 473 had a cat only at baseline, 651 acquired a cat during the follow-up, and 700 had a cat at both evaluations. Two hundred thirty-one subjects (3.7%) became sensitized to cat. In a 2-level multivariable Poisson regression model, cat acquisition during follow-up was significantly associated with new-onset cat sensitization (relative risk = 1.85, 95% CI 1.23-2.78) when compared with those without a cat at both surveys. Preexisting sensitization to other allergens, a history of asthma, nasal allergies and eczema, and high total IgE level were also significant risk factors for developing cat sensitization, while cat ownership in childhood was a significant protective factor.

Conclusion. Our data support that acquiring a cat in adulthood nearly doubles the risk of developing cat sensitization. Hence, cat avoidance should be considered in adults, especially in those sensitized to other allergens and reporting a history of allergic diseases.

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