I developed some blacklish layer on both sides of my penis glans nearly 4 months ago.I consulted an dermatologist regarding it ,he ruled out fungal and bacterial infection and said that its frictional dermatitis and harmless but he suggested me to use efficort cream but no such improvement.there is no pain, no itch nothing except that blackish layer on glans.When penis becomes erect that blackish layer looks like grey.How to get rid of it plzz help.