Why does my allergy to cats only act up once in awhile?
I live with a cat who mostly stays in my roommate's room, and although in the past I have been highly allergic to cats, this cat doesn't bother me most of the time, even though she has long hair. My allergic reactions don't seem to be tied to her being around me, either.
Interestingly, allergies do not always behave in a predictable way. For example, you may have been very allergic to cats in the past, but over time you're allergy has fizzled to a much more reduced state. This happens especially in people who are exposed to low levels of the allergen over time. This sometimes allows the body to become less sensitive to the allergic stimulus. Another possibility is that this particular cat does not release the type of cat dander that you react to. One way to tell is to test your symptoms around another cat. If you don't react to that cat either, then you may not be allergic to cats at all anymore.
If you have more questions about what you are allergic to, or if you do have an official allergy to cat dander, then you should schedule an appointment to see an allergist. He or she can perform allergy testing so that you know which of the common allergies you have. In addition, the allergist can recommend strategies to avoid allergens. If you are in a situation where exposure to them is inevitable, then you may benefit some day from an allergy desensitization. This is a procedure in which you are systematically exposed to the allergen in increasing amounts so that your body gets used to it. Good luck.