My Chi is asthmatic and has allergies to grass and other substances.
He was put on cortisone for a long period of time and started losing his hair. Concerned about his long term health, I changed to another vet who refered him to a specialist.
The specialist put him on Aminyllin tabs. morning and night and he hasn't looked back.
Very occasionally, he will have problems with grass allergies - he licks his feet which appear red and inflamed, so I give him Polaramine for a day and that settles it.
But reading Blitznbears response, I'm goin to add flaxseed. He already has fish in his diet.
Hope this helps.