There are a lot of small red dots on the arms and thighs may be due to capillary hemangioma, allergic purpura, perifollicular keratosis, it is recommended that the patient under the guidance of a doctor to clarify the specific cause of the disease after treatment through drugs or laser and so on. 1. Allergic purpura: allergic purpura, also known as IgA vasculitis, is a kind of non-thrombocytopenic purpura, which can be treated with oral compound glycyrrhizin tablets, vitamin C and rutin tablets. 2. Perifollicular keratosis: Perifollicular keratosis, also known as hairy moss, is a kind of follicular keratinizing skin disease. It can be treated with topical urea cream or ammonium lactate lotion. 3. Capillary hemangioma: capillary hemangioma is generally caused by the abnormal proliferation of endothelial cells in blood vessels, in the treatment can be treated by laser, such as carbon dioxide laser, 595 pulsed dye laser and so on. When there are a lot of small red dots on the arms and thighs of the patients, there may be other reasons, it is recommended to go to the regular hospital in time for examination and treatment, and the above medicines need to be standardized treatment under the guidance of professional doctors.