Millions of people are allergic to cats. Symptoms range from eye irritation to potentially life-threatening asthma attacks. One can develop an allergy at any age. Allergies most commonly develop to proteins. In cats, a protein called Fel d 1 is the primary culprit. The amount of Fel d 1 present does not differ between breeds, but can vary among individual cats. However, there are many safe, effective ways to deal with cat allergies, so you don't have to give up your cat OR your friends!