My Cocker Spaniel baby has been struggling with allergies and itchy skin for several years and it has been an uphill battle. We started with using a doggie antihistamine with a small amount of steroid called Temeril P that you get from the vet. It helped some but wasn't super successful and I don't like giving her a steroid. She gets staph infections from all the scratching so we have been periodically putting on antibiotics to get her skin healed up.
Here are some of the things that have been helpful to her:
I've recently discovered that a rinse in chamomile tea helps a lot to calm her skin and stop the itching for a while. Make two cups of chamomile tea, using about 6 tea bags to make it strong. Let it cool and pour it into a spray bottle, then add warm (not hot) water and spray your dog's skin all over to relieve the itch. I've also rinsed my girl with witch hazel which offers some relief as well, but the chamomile tea has been the best so far.
Another rinse that has helped is 1/2 cup green tea mixed with 1/2 cup apple cider vinegar and 1 cup purified water (You can boil for 20 minutes to purify). I double or triple the recipe to fill my spray bottle and spray my baby girl all over for some relief to her inflamed skin.
Apple cider vinegar solution (50% apple cider vinegar/50% water) to rinse or wash your dog in can restore the skin's acidity, kill off pathogens, and soothe the itch. You can also add a bit of apple cider vinegar to your dog's water to help from the inside as well.
I have a labordoole who was miserable. Found on Pinterest to put olive oil on his food. He weighs 85 pounds I put one tablespoon on his dry food, in one week he has almost completely quit scratching.