Brown spots on the inner thigh root may be caused by seborrheic keratosis, hyperpigmentation and ringworm. 1. Seborrheic keratosis: the cause of seborrheic keratosis is still unclear, and it is considered to be related to skin aging, heredity, gene mutation and so on. Patients will appear light brown, black spots, flat papules and other manifestations. If patients have seborrheic keratosis on the inner thigh root, there will be brown spots. 2. Hyperpigmentation: Hyperpigmentation is considered to be caused by heredity, sunlight exposure, endocrine abnormality, inflammation and so on. Patients will have light brown, gray-blue, brownish blue, blue-black pigmentation. If the patient has hyperpigmentation on the inner thighs, it will be manifested as brown spots. 3. Tinea cruris: the pathogenic fungus invades the inner groin caused by ring or semi-ring lesions, the patient will have light brown, brown, reddish ring rash, covered with a little scales on the lesion area. Therefore, patients with tinea cruris on the inner thighs will be manifested as brown spots. Patients with brown spots on the inner thighs may also be eczema and other causes, it is recommended that timely medical treatment, the doctor will choose the appropriate measures according to the patient’s condition treatment.