Never give an ocicat something he is allergic to.
Of course, I would never give anyone, cat or otherwise, something they are allergic to knowingly, but nevertheless I managed to do so yesterday. I noticed we'd run out of cat food after arriving at home, so instead of getting the usual stuff from the pet store I got him some food from the corner shop. Wet cat-food made from rabbit-meat.
He has never had rabbit before. And he loved it.
He loved it right up to the point where an apparent allergy kicked in and he started itching all over. Ocicats being an intensive breed, this escalated to the point where he scared his mother shitless. This resulted in a hissing contest and a lot of running around the appartment and intermittent fights (most of the energy dissipated in a cat fight is in the audible part of the spectrum). So at 0430 in the morning it sounded like I was trying to murder someone in the appartment and that the person wasn't going to go without a fight.
I got up, put on a thick jacket and oven mitts in order to restore peace and order. The respective cats being on either side of a door (which I duct-taped shut), I quickly inspected the cats for damage, checked that Snoopy wasn't having any issues with his airways and went back to bed.
Snoopy looked a lot better this morning. Still itching, but at least he was eating (not rabbit!) and he woke me up by making a quick raid and biting my nose (which he does when he thinks I have slept long enough).
Okay then, so I won't be feeding him rabbit anymore.
I called my mother today to ask her opinion (she is a veterinarian). I saw no point in calling her during the night since Snoopy didn't seem to have any reactions to it other than itching like crazy and being scared. The advice she had was to do pretty much what I had done (leave him alone as much as possible to calm down, separate him from the other cat and ensure he had no threatening symptoms).
She also said was that it is best to choose a high quality brand of cat food and stick to that exact type of food. Don't vary what you give your cat (provided that the food has all the nutrients your cat needs) and only feed it food you know they have eaten without any problems before. She also said that if he were to ingest what set off the reaction again, the next time would be worse -- possibly even life-threatening. She noted that it may not be the meat that set it off, but one or more of the additives. So stay away from all food by the same manufacturer if your cat is allergic to one of the types -- it may be the additives they use. Also, dry foods are generally better than wet foods (I think she said something abut there being fewer additives or additives that are lower risk).