Certainly if his line of dogs has allergy issues, it could be caused by inbreeding….

However, MANY mixed breed dogs have the same exact issue and its usually caused by a food intolerance. Your dog may be well-served to go on a different diet. Many dogs have improved drastically when moved to a raw, prey model diet that is comprised of different protein sources than what they've been fed on kibble.

Steroids MASK they issue .. they do not cure the cause. Find the cause and move from there. You may want to find a homeopathic vet to consult with.

Edit: Vets are not God. Trying another vet rather than subjecting your dog to misery itching and sneezing combined with longterm debilitating steriods seems a prudent thing to do. Certainly it is easier to just go with the flow – but we're talking the life of your dog here.

It sounds like he has allergies.
Have you tried eliminating common allergens from his environment?
Food allergies are very common, and relatively easy to address – I would start with that.

I am fostering a chihuahua who came to me with food allergies.
She was VERY itchy, had a "hot spot" on her leg, was missing hair in places, had very dry skin and coat, and her ears were red.
I put her on a lamb and millet kibble, and cut everything with corn, soy, chicken and beef from her diet. I baked her yams for treats, and gave her cod liver oil for the first two weeks (vitamin A and fish oils are good for the skin and immune system), and regular fish oils every day.

After a month she had healed up, and no longer itches like she used to. She is still missing hair in a few spots, but I think they are starting to fill in.

Regardless of the cause, I think anything you can do to improve your dogs health without steroids is worthwhile.

He sounds like an allergy dog… Allergies like in people can start at any time. Typically though, breeders shouldn't/wouldn't breed a dog with allergies.
Some of his behavior could be due to poorly being socialized as well, no matter how good of the bloodlines were, training-or lack there of- can sometimes make or a break a dog. Then again, some breeders don't do temperament testing.

What about using a product like Atopica, or a combination of injections(Heska testing). You could even up your dose of anti-histamines to cut down the use of steriods.

well I do have a nearly 12 yr old dog with a genetic health problem that makes allergies look like small potatoes (he would have been DEAD 8 yr ago without continuing expensive medication) and I can trace it to both sides of his family tree but the 5 generation inbreeding coefficient is ZERO – NO COMMON ancestors in 5 generations. Furthermore ALL the affected relatives were diagnosed after he was born AND the fact the problem is genetic was not considered proven till after he was born…BE careful of assumptions- all problems are not the fault of inbreeding nor can the breeder always be blamed- they are only human……

actually allergies frequently respond to a food change