Fungal infection.. Also called jock itch, when occurs in groin.. 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, bacterial and viral infection, doctor need to see to confirm the diagnosis..So, meet me in my clinic or do direct online consultation by sending photos for detailed information and medicine for treatment.

Need to Visit dermatologist for making diagnosis and management

when proper lubrication is not present during coitus due to friction it can induce redness and irritation on the glans... use lubricating jelly (KZ jelly)during intercourse if sufficient lubrication is lacking... you can try this for a few weeks. if it persists then send your pictures to me through private online consult & get it assessed to rule out candidial balanitis or zoon's balanitis . hope this is helpful .