Sun spots are medically known as solar lentigines, and solar lentigines on the arms can be removed by removing the causative agent, medication, and other methods. Sun dermatitis is an inflammatory erythema caused by sun exposure and is usually of acute, transient onset. Generally, sun spots fade away when the trigger is removed. When sun spots appear on the arm, pay attention to sun protection, such as playing umbrellas, etc., most of them subside within 1~3 days. If the symptoms are more serious or there is edema of solar dermatitis, you can use glycerite lotion to relieve the symptoms, with oral antihistamine drugs such as loratadine. If hyperpigmentation occurs, it can be applied to the targeted treatment, such as cumulonimbus ointment. Suffering from solar dermatitis is recommended to go to the hospital in a timely manner, the use of drugs should be under the guidance of medical professionals to avoid adverse reactions.