The over the counter stuff (Benadryl, Claritin) has a minimal effect (if any).
Obviously your dog’s condition is more serious, so the vet has to go with a prescription drug like Apoquel, some dogs do well on it, but long term I might be concerned about side effects, the same thing with steroids.
Without testing and identification of the allergens by a dermatologist, a veterinarian has no choice but to try band aid treatments to stop the symptoms in an attempt to keep the dog comfortable.
I would ask the vet for a referral to a specialist in your area.
