t know what is the cause of this, considering you have tried more or less anything, so far to treat it. However, I know herbal
remedies do often work (not always, but it might be worth trying if you are interested.) I'd try bathing the affected areas with a tea made of Burdock Root / Marigold Flowers / Yellow Dock. A teaspoon of each/1 cup boiling water/steep15 mins/strain/cool. Use on a pad of cotton wool 3-4 times a day.