There are many reasons for the appearance of small red dots on the arms without pain and itching, such as vascular nevus, allergic purpura, perifollicular keratosis, etc. It is necessary to seek medical attention to improve relevant examinations, clarify the causes, and apply drugs to actively treat them under the guidance of doctors. 1. Vascular nevus: It is caused by abnormal development of vascular structures or abnormal proliferation of vascular endothelial cells, and can appear as dark red or burgundy dots on the arms, with the form of flat or slightly It is a nodular thickening superfluous organism with no pain and itching. Vascular nevus is mainly treated by local topical medication and systemic medication, assisted by laser, freezing or local injection to relieve symptoms; 2, allergic purpura: allergic purpura has complex causes and can be caused by bacteria, virus, food, drugs and other causes. The clinical manifestation is a red rash on the arm, which can gradually develop into a pinpoint to soybean-sized purpura, without pain and itching in mild cases, and can be accompanied by gastrointestinal reactions in severe cases. Most allergic purpura is self-limiting and can be relieved by topical glucocorticoids; 3, perifollicular keratosis: also known as hair moss or hair keratosis, is a chronic follicular keratosis skin disease, may be related to autosomal dominant inheritance, vitamin A deficiency, metabolic disorders, occurring in the upper arm and thigh extension, symmetrical distribution, occasionally see the pan-distribution, manifested as a small red papule on the arm, skin There is a rough feeling, usually without pain, itching and other uncomfortable symptoms. This disease can be topically applied with topical vitamin A acid cream or salicylic acid ointment, which can soften or dissolve the keratin and thus improve the symptoms; 4. Hemorrhagic rash: It is formed due to blood accumulation in the tissues of the skin and mucosal vessels, which is manifested as a rash of varying sizes and can also develop into petechiae, but without itching and pain. Patients are advised to go to the hospital promptly for examination after symptoms appear to clarify the cause of bleeding so as to treat the cause as well as the symptom.