The red rash on both sides of the thighs may be caused by ringworm, eczema, contact dermatitis and other reasons. 1. ringworm: itchy red rash on both sides of the thighs may also be ringworm, caused by fungal infection, often from other places. 2. Eczema: may be local wear thicker or not cotton clothes, the skin is not breathable, resulting in contact with the site of the inflammatory reaction, accompanied by red rash, itching and other symptoms, the serious can appear point-like erosion, oozing. 3. contact dermatitis: due to contact with some easily sensitized or irritating substances and lead to the occurrence of metamorphosis, can be manifested as erythema, papules, itching and other symptoms, will also appear on both sides of the thigh rash. Rash on both sides of the thighs is recommended to go to the hospital dermatology examination, clear cause, under the guidance of the doctor for treatment.