I have a dry itchy red rash under my hairline, arm pit, under breasts, and groin . I was checked for psoriasis , excema, and yeast infection . I was told I have dermatitis and that I m alergic to something, but when tested for common topical chemicals common in bathroom/makeup products I was found not allergic. Could it be dust mites or a food allergy? I ve had the rash over a year now. When I was in a hot sunny climate (Costa Rica) it went away.