Suggest Treatment For Severe Itchiness In The Armpit

I have dry flacky skin that is exsteremly ichy under my arm pit and between my scrotum and anus. I have had this rash for 2-3 years now treated it for yeast, fungus, nothing helped until a doctor proscribed triamcinolone cream, this would completely remove the rash as long as cream was applied daily, 2 days without and it will return. I have tried moisturizers oils anything that was suggested to me nothing has helped I even changed my eating diet. Any ideas