Antihistamines can be helpful in some cats with atopy (pollen and dust allergies) but are not likely to be helpful in cats with food allergy (since the only effective treatment for food allergy is the hypoallergenic diet and nothing else orally but water). I do not often use benadryl in atopic cats, but I have had some success with chlorpheniramine 2-4mg/cat orally twice daily. In some cats, antihistamines can cause sedation; rarely antihistamines can cause paradoxical excitement, so discontinue them if side effects occur. Topical benadryl or hydrocortisone cream can also be tried on localized areas of skin inflammation, but since cats groom themselves, topical products may not be particularly helpful.
Kimberly Coyner, DVM DACVD
Dermatology Clinic for Animals of Las Vegas
It has never been determined if the allergy is atopy or food sensitivities. I don't want to put him through a biopsy due to financial reasons and of course the trauma.
Along with my Vet I have introduced every possible form of hypoallergenic diet and he refuses to eat even when mixed at 90% his usual to 10% hypo...he starved himself for 3 days until we/I had to give in and feed him the only alternative to chicken that I could find he would eat and that was fish and only thru a brand I had formerly refused to use.
Yes we did try the Venison and everything else my Vet could order in...
The only other suggestion he has is to use Atopica medication.
Is this medication also for food allergies?
Skin biopsy can be supportive of allergic dermatitis, but not specific for food vs. atopy. Unfortunately, blood allergy testing for food allergy is not accurate in animals; the test and treatment are the hypoallergenic diet trial. The hardest part is finding a hypoallergenic diet that a cat will eat; I have found the most palatable are the prescription formulas Royal Canin HP23 and Hill's z/d. If they won't eat these, I try Royal Canin rabbit/pea and then over the counter Natural Balance duck or venison and pea as a last resort.
Atopy is diagnosed by persistence of symptoms despite a hypoallergenic diet trial and elimination of skin parasites such as fleas and mites; once the diagnosis of atopy is made then options are to treat symptoms (with medications such as antihistamines, fatty acids, steroids, or Atopica), or to perform allergy testing and desensitization injections to identify and treat the cause of the itch and try to minimize need for other medications. Atopica (cyclosporin) is helpful for many cats with atopic skin disease, but is not particulary helpful for food allergy; it would be worth trying if antihistamines are not helpful since it does not have steroid side effects. However since it is still a potent immunosuppressive drug, bloodwork and toxoplasmosis titers are recommended prior to starting Atopica, and then bloodwork to monitor internal organs is recommended at least 1-2 times yearly.
Hope that is helpful,
Kimberly Coyner, DVM DACVD