First for a little back story... I have four cats (two males, two females, all different ages, strictly indoor only, declawed front and rear, and all have consumed the same food for life). Until last year, I never routinely put topical flea medication on the cats because we have never had problems with fleas. About a year ago, all my cats went to stay with my mother while I was out of town. My mother has four cats of her own, and has kept all the cats in the past. She does, however, have a cat diagnosed with "flea allergies" that is prone to scab outbreaks and irritation. She has to take him for cortisone injections frequently and keeps topical flea meds on the cat. After returning home, my youngest cat (Phoebe, 4 years old) began showing the same symptoms. I rushed her off to the vet because the scabs and swelling was quite severe, especially around her neck. I could not figure out how she was getting such scabs since she does not have back claws and many were in places she could not bite. The vet said she had flea allergies and administered a cortisone shot. He suggested I put a topical flea medication on all my cats for good measure, so I did. Phoebe's symptoms cleared within the week, and I continued to give her either Frontline or Advantage each month. One month, I was a little late on administration (about 3-4 days), and all of Phoebe's scabs and irritation returned. Her symptoms did not improve after the meds either, so we returned to the vet for another cortisone injection. I know that Advantage/Frontline are supposed to be administered every 28-30 days, however, I now have to give Phoebe the meds every 20 days or her symptoms return. I am also keeping the topical flea medication on the other animals as well. I do not understand how a cat just "develops" a flea allergy like this. I have yet to find a single flea in my home. I vacuum almost everyday and we even got new carpet in the house just 3 months ago. Also, her coat never recovered from the first "allergy attack". Before, her coat was always very thick and shiny. Now, especially on her back, the fur looks thin and dull. I've tried medicated shampoos also, but nothing seems to help. I do not want her to continue going through this, and I just don't think fleas are the culprit. Also, the topical flea medication appears to be losing its effectiveness. I've tried Frontline and Advantage, but her scabs return if I don't administer it earlier and earlier. Any suggestions would be appreciated.