Adults who get their first cat double their risk of cat allergy -- especially if the cat is allowed in the bedroom. But adults who had cats as kids are less likely to become allergic to their new feline pets, a large European study finds. An adult’s risk of developing a new cat allergy over a nine-year period “was nearly doubled in those acquiring a cat,” report Mario Olivieri, MD, of the University of Verona, Italy, and colleagues. “Interestingly, this effect was confined to those allowing a cat in the bedroom.”