Skin allergies are tough. What are you feeding? Pictures of any spots on the skin.
What kind of shampoo are you giving baths with. Too many baths can take out the natural oils in the skin and dry out the skin and cause dander.
Skin allergies can be food related, allergy to fleas or environmental factors.
First is try and change what you are feeding.
Have these spots tested.
Try and use the Search on this site and find other posts.
Try adding Omega 3 Fish Oil (like ones made from the smaller fish like Sardines, Mackerel and Anchovies) to meals.
Baking soda can calm itchy skin.
You can make a spray of 1Tbsp of Baking soda and 8oz of water in a spray bottle and spray the skin. Make sure you shake the bottle every time before you spray it on.
You can also spray a mix of coconut oil and water on the coat. It alleviates the skin dryness, as well as giving their coat a shine. You can also add coconut oil, just a small amount like 3/4 teaspoon once a day, to the food to help with skin dryness.
For shampoo we use Dog O Suds, it is not soap just essential oils that won't dry out skin or coat.