Itching sensation on arms and legs may be a disease such as photosensitive dermatitis, pruritus, urticaria or scabies. 1. Photosensitive dermatitis: It is caused by skin allergy to ultraviolet rays in sunlight, and is easy to appear in people in high latitudes and southern regions, mostly in summer, and itchiness may appear on arms and legs. 2. Pruritus: the cause of the disease is more complex, commonly found in the elderly, may be too frequent baths, the use of alkaline shower gel, sebum secretion reduction, etc., may also be related to diabetes. 3. Urticaria: It is a kind of allergic skin disease, mainly caused by body contact with certain allergens, and the main contact pathway is inhalation, ingestion or direct skin contact. Common allergens include pollen, mites, seafood, and low quality skin care products and hair dyes. 4. Scabies: The disease is caused by scabies infection, mainly through skin contact, but also through contact with towels, bed sheets and other indirect transmission. Long-term travel accommodation or sexually active people easy to infect, serious cases can appear in the arm or leg pimples, itching, night symptoms aggravated. It is recommended that patients with itchy arms and legs go to regular hospitals in time for a clear diagnosis and standardized treatment under the guidance of doctors.