It is possible to become allergic to something that you were once ok with i used to have dogs ,cats,birds but when i married my husband doesn't like dogs,cats,birds,any so haven't had a pet for years and now if i visit my mums or friends both have cats I'm ill for days after feels like hair in my throat an my eyes water real bad ,i think if you haven't been in contact with some things a long time its perfectly possible to become allergic you could consider antihistamines and see if it settles if not you may have to re-think having cat as a pet

 If you had been with cats through out your life then it is nearly impossible that you develop cat allergy now. What my minds says is that there is some problem with your cat and not you yourself. Get her washed and get her checked through some vet. The cat you have might have fur that is allergic to every one, or at least you. Keep another cat with you and see do you find that allergic too, but of a different specie.

 It's possible to develop allergies, I myself am falling prey to it, and I LOVE cats! I will not get rid of them. I have also been informed that it might not be all of the cats that I am allergic to, but just a certain type of hair from one or two of the cats. I am leaning toward long hair, as I didn't really develop this until my daughter made me adopt her kitten, whom is a long hair. Benadryl is effective in keeping allergies at bay. Hope this helps, good luck.