This is a fungal infection found in warm, moist areas of the body. Commonly it is in the groin or inner thighs. It is otherwise known as ‘jock itch’ as it is common in athletes.
The rash is erythematous, scaly, and very itchy. It has a red, raised border (sometimes with small blisters) and can look similar to ringworm (tinea corporis).
Treatment is usually with topical anti-fungal creams and sometimes topical hydrocortisone in addition. Oral anti-fungals can be used if topical treatments don’t work.
References
https://www.mayoclinic.org/diseases-conditions/jock-itch/symptoms-causes/