Armpit long round spots may be related to lichen planus, pityriasis rosea, tinea corporis and so on. 1. lichen planus: commonly known as sweat spot, is the skin fungal infection caused by malassezia invasion of the skin epidermis. It may grow in the armpit, and the lesions may gradually expand from a small dot-like rash to a flaky rash with a scaly surface. 2. pityriasis rosea: may be closely related to drugs, immune response, infection and other factors. It may appear as rose-colored, light red patches that can grow under the armpits and look like brown, round spots. 3. Tinea corporis: mostly caused by fungal infection, the clinical manifestation is scaly annular erythema, around which small blisters may appear. The onset of ringworm is related to obesity, developed sweat glands, weak immunity, and fungal skin infections. The appearance of underarm long round spots, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions for further examination, with the help of the doctor to clarify the cause, and targeted treatment or treatment.