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Most of the over the counter flea meds (with the exception of Advantage that recently went OTC) are not overly effective and some can be toxic in cats so be careful. I would discuss the use of a product such as Frontline for fleas which may be better for long term therapy since the flea is the intermediate host for some species of tapeworms. This may reduce the odds of having to use the profender again. In the event you do buy frontline, advantage or revolution, I would wait about a week after applying the profender before applying the other treatment. I hope this helps and gives you direction.
Any topical can cause some mild irritation, but if you have an active flea issue, this could also be the culprit. You may ask your vet about a oral flea product called capstar. This is a short term treatment until you can apply a topical but it will help. You may also discuss a treatment with your vet that will reduce the irritation such as a antihistamine or steroid. These will at least provide relief until you get the flea problem under control. If you need to control the environment and you decide to use a spray, bomb or fogger, the key to success is vaccuum all surfaces first, the use the treatment, then repeat the vaccuuming. You then repeat these steps in exactly 2 weeks. The prevaccuum help hatch eggs so the hatchlings can be killed by the fogger. Just an extra thought.
I hope this helps and gives you direction.