obsessive itching and twitching

Question
Our male cat, from a rescue, has been obsessively licking himself since this spring, which was very rainy in this area.  His tail also twitches.  We wormed him, stopped feeding him canned tuna, switched to a chicken and oat dry food.  He has been to the vet and given Decadron.  He is an indoor cat, neutered, black short hair.  We also have a neutered male, long hair cat from the same rescue.  Any assistance would be appreciated.  Thank you

Answer
Nancy,

It sure sounds like an allergic reaction to me, but I am not a vet.  It could be body mites and a treatment with ivermectin once a week for 4 weeks would clear it up.  If it is not body mites, the ivermectin treatment will not hurt and you can rule out a number of skin parasites.

Another major allergy is fleas, so you can check for that.  There are good topical treatments these days, so you can treat for fl;eas even if none are readily apparent.

Many cats are allergic to corn, wheat, and soy, especially the gluten, so double check your food, but it sounds as if you have looked at that.

Finally, allergies can also be to things in the environment, e.g. whatever you wash the bedding in, certain fibers, etc.  Allergies are a royal pain to nail down.

Please let me know how you make out.

Best regards... Norm.