Black patches on the skin may be caused by diseases such as acanthosis nigricans and seborrheic keratosis, which can be treated by applying medication, radiotherapy and chemotherapy, as well as laser and surgery in accordance with doctor’s instructions. 1. Acanthosis nigricans: Acanthosis nigricans is related to heredity and obesity, which can easily lead to melanin deposition in the folds of the skin, resulting in black patches on the skin. It can be treated by applying medicines such as vitamin A cream and cod liver oil ointment, and patients with malignant acanthosis nigricans also need to be treated with radiotherapy and chemotherapy. 2. Seborrheic keratosis: Seborrheic keratosis is related to heredity and skin aging, which will lead to black plaques on the patient’s skin with skin aging. It can be treated with laser therapy and surgical excision. Coffee spots can also cause black patches on the skin, patients need to consult a doctor in a timely manner, after the cause of the disease is clear, in accordance with the doctor’s instructions standardized treatment.