Fungal infection or Ring worm.. when occurs in groin, called as jock itch.. Usually fungal infection is common in moist areas of body like skin folds..It's mostly circular or round in appearance.. May be red or black in colour.. Treatment depending on the type and severity.. Avoid sharing clothes, towels and soap; sweating also increases it..As it has to be differentiated from eczema and infection, its a must to see and confirm the diagnosis for proper treatment..So, please send photos of the affected area for accurate diagnosis and treatment.

It may be eczema. Please send photos using online consult option for proper examination diagnosis and treatment

The description fits that of Dermatitis secondary to an allergen or an irritant. Do share images.