Symptoms of arm itching may be caused by allergic skin diseases, ringworm, psoriasis, pruritus, neurodermatitis, lichen planus and other diseases. 1. Allergic dermatosis: common allergic dermatosis such as contact dermatitis, urticaria, drug rash, photosensitive dermatitis, etc., through is due to the patient’s contact, inhalation, injection, ingestion, etc. so that the allergen enters into the body, causing the skin to appear erythema, pimples, itching, redness and swelling and other symptoms. 2. Ringworm: this disease is caused by fungal infection, often manifested as erythema, pimples, flaking, accompanied by itching and so on. 3. psoriasis: the cause of this disease is not known, may be caused by genetic, immune and other factors, trauma, infection, etc. can make the condition worse, the patient may appear on the arm scaly erythema with itching. 4. itching: the cause of the disease is not known, may be too dry skin, drugs and clothing stimulation, etc., sebaceous glands sebum secretion can lead to itching. 5. Neurodermatitis: the occurrence of this disease may be more related to mental psychological factors, but also with certain diseases, diet and so on. Patients can appear in the arm red or brownish-yellow spots flat papules, and the skin grooves deepen, the skin ridge elevated, showing moss-like changes, accompanied by itching and other symptoms. 6. Lichen planus: the cause of this disease is not yet clear, may be related to heredity, metabolic disorders, immune disorders, drug stimulation, or viral infection. Patients can appear on the arm of the border clear purplish red polygonal flat papules, with wax-like luster, with itching and so on. In addition, arm itching may also be caused by certain internal diseases, such as diabetes, etc. It is recommended that patients go to the regular hospital in time, relevant examinations, a clear diagnosis, and then follow the doctor’s instructions to receive treatment.