Here are some of the things I have tried over the years. Different things work for different dogs.
There are some good dog shampoos and conditioners on the market for this type of problem some work for your dog and other don't. Depends on the reason of the issue and sometimes that is hard to tell.
I have had good luck with oatmeal based ones and a product called DerMagic. DerMagic isn't cheap though so I would try the oatmeal stuff first for itching, etc.
If the skin is dry you can also use a leave in conditioner.
It never hurts to work from both the inside and the outside. Fish oils, Vit E, olive oil, etc can all help as well. Just don't over to it or they will have GI issues.
Also this can be a stress thing if something in your life and his/hers has changed you may be able to correct the issue.
If you think it is pollen based you can also wipe the dog down when they come in to remove some of the pollen.
Just thoughts from a dog loving person that suffers from allergies.
My nephew has a yellow lab that appears to have allergies. In the spring he gets VERY itchy, to the point of having major areas of no hair because he is scratching it off. This only happens in the spring so I don't think it could be his food. The vet gave him steroids to give him and he told him to bathe him in anti dandruff shampoo. But after bathing him the last time, it made it MUCH worse. Any suggestions on what he can do to give relief to this poor dog. I have told him to give him benedryl twice a day. It has settled down some for now. Thanks it advance for any suggestions.