Is there a flea coller on your kitty, could be an alergic reaction.  Cats
should be bathed infrequently because you remove oils from the fur that help
repel water and keep the skin from getting too dry.

If it is not causing discomfort, give it a few more days to clear up.  A vet
can give you something topical for it but if it gets bad, a Steroid shot
(prednazone) may be in order.  It still may be fleas, they don't permanantly
reside on pets but jump on and off as they please.  Check for flea dirt
(black sand like grains) on your kittys tummy.  Treat all bedding areas and
cat accordingly.