If you have brown spots on the roots of your thighs, it is likely that ringworm is caused by a fungal infection. Ringworm usually occurs at the junction of the mucous membranes of the skin, where moisture and sweating can easily lead to the growth of fungi. Ringworm is accompanied by a pronounced itching sensation, usually with a heavy peripheral inflammation and a tendency to heal itself centrally, and the periphery is accompanied by flaking at the same time. The main treatment is topical antifungal medication. Since the skin in the groin area is relatively thin and tender, it is important to choose a mild and non-irritating topical medication for treatment. Try topical bifenazole cream, applied in small amounts once in the morning and once in the evening, and be sure to wear loose pants to avoid local dampness and sweating.