Hello,
Without examination,it is very difficult to confirm a diagnosis,but it can be erythrasma(chronic
skin condition affecting the
skin folds and caused by bacterium corynebacterium minutissimum) , acanthosis nigricans(abnormal thickening and darkening of the skin, especially in body creases),hyperkeratosis(thickening of the skin due to excessive accumulation of keratin in the outer layers of the skin) and hyperpigmentation(patches of skin become darker in color than the normal surrounding ski