A few red pimples on the roots of both thighs are considered to be caused by contact dermatitis, folliculitis and ringworm. 1. contact dermatitis: its cause is mostly related to skin contact with exogenous substances, including underwear, sanitary napkins and so on. The patient’s epidermis will appear erythema, edema and papules and other symptoms. 2. Folliculitis: Folliculitis may be caused by pathogens infecting the hair follicles, and factors such as excessive sweating, friction of the skin, and irritation of the hair follicles may also induce the disease. The patient’s body will appear red papules, pustules and other symptoms, common in the thighs, buttocks, groin and other places. 3. ringworm: due to the inguinal skin infection caused by fungi, there will also be a few red pimples on the root of the leg, accompanied by itching and other symptoms. There are many reasons why there are a few red pimples on the roots of the legs, so it is recommended that the patients go to the regular hospitals for relevant examinations to clarify the causes of the disease.