I spend a lot of time on this blog harping about the importance of flea prevention. Fleas carry a number of animal and human diseases (such as tapeworms and bubonic plague, respectively). In pets, fleas contribute to skin rashes, ear infections and itching anywhere on the body. They have been implicated in syndromes, such as feline asthma, that are caused by an overactive immune system.
I often see pets with skin problems and recommend flea control as the first step. I can’t count the number of times that recommendation has been met with the following comment: “But my pet doesn’t have fleas!”
In these cases I recommend flea control nonetheless, because even an occasional flea bite can trigger skin or ear problems in a sensitive individual.
But the situation is different in your case, Carol. First, you don’t mention that your cat is experiencing any skin, ear, or other problems. And you have reason to believe that she has reacted adversely to a flea preventative in the past. Such reactions are rare, but they do occur.
In your cat’s case, I don’t think flea prevention is mandatory.
However, if your cat develops any of the problems I have listed above, or if you see any fleas or their feces, it will be time for a trip to the vet to discuss alternative flea control products.