Itchy granular dots on the arms can be caused by hairy moss, contact dermatitis and folliculitis, which can be treated with medication as prescribed by your doctor. 1. hairy moss: arm if full of small granular skin damage, and have very itchy symptoms, may be suffering from hairy moss disease caused by. You can follow the doctor’s instructions to apply salicylic acid ointment and urea ointment and other drugs for treatment. 2. contact dermatitis: the patient may also be due to contact with allergens caused by the arm long a lot of particles and itching symptoms occur. You can take levocetirizine hydrochloride tablets, olopatadine hydrochloride tablets and other drugs as prescribed by the doctor for treatment. 3. Folliculitis: if the patient often scratching the arm, may cause arm folliculitis, thus showing a lot of granular dots on the arm and itchy phenomenon. If the symptoms are mild, generally no special treatment, if the symptoms are obvious, you can follow the doctor’s instructions for external mupirocin ointment, fusidic acid cream and other drugs for treatment. Therefore, if the patient appears to have a lot of granular dots on the arm itchy symptoms, it is recommended to go to the hospital in a timely manner, to clarify the cause of the disease, choose targeted treatment.