You can bath him with a tea tree oil shampoo as it is an antiseptic and will help to clear up the problem topically. But the product to use to get to the cause of the problem is Seacure by Proper Nutrition. It was what fixed my dogs skin problems. If you go to Proper Nutritions web site there is an article from the whole dog journal you can read.
Best of luck with your Welsh!
Best of luck with your Welsh!