I swear the fleas are getting resistant to frontline. I went to a conference last winter and the speaker said they had found fleas, in Florida, that are resistant to frontline.
So the most likely cause of his problem is flea saliva allergy.
I would try "advantage" drops instead.
I would also add "lufeneron" which makes it so the fleas can not reproduce.
It is called "program." It comes in drops you can put in the food or pill form. the vet can also give it as an injection.
You can order it on amazon link
There is also an oral product called "capstar." It is a pill you give to kill the fleas. It works very well. I watch the fleas fall of the pet, dead. But each pill only lasts for 24 hours. You may want to try a few just to give him some relief. You can buy it amazon too.
I am not sure which itching spray you are using. I would try a hydrocortisone spray if you have not already tried that.
You can also give him an antihistamine for itching. Try chlopheniramine 4 mg tablets. Give 1/4 tablet every 12 hours.
If he does not have flea allergies, he may have food allergies.
Food allergies, in cats, shows up as skin lesions. Food allergies can develop over time. To determine if he has food allergies, he would need to be put on a completely hypo-allergenic diet for 6 weeks. The name of the diet is called "hills z/d." You have to get it from a veterinarian. There are no over the counter diets that will work for the food allergy test.
He could also have environmental, or inhalant allergies, which is called "atopic dermatitis." Your vet could do a blood test to see what he is allergic to. Then you could try and avoid what he is allergic to. She could also receive "allergy shots" to desensitize her to the allergens. Allergy shots are 50-70% effective in pets.
I would try treating for fleas, and flea allergies first.
I hope this helps.
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