My dog is loosing his hair. I have had him to the vet because he suffers from allergies and he gets a shot every month. Now he has fleas, the itching is worse and I don’t want to drug him up. He’s a black lab.

ok my dog has really bad food allergies we have him on a prescription diet and it was working when my brother had him and now he still is scratching himself constantly and making himself bleed. i havent been able to bathe him lately because the last time i didnt he broke out in hives. i just got a new shampoo from another vet by prescription only that is soap less and will help with the hives i dont know what to do i am at my whits end. this is a family dog who my family has had for over 8 years now he is between 9-11 we found him and just kept him i do not want to have to euthanize him has anyone gone through this and had a positive out come
any advice would help sorry so long thanks in advanced