Children with white spots on their arms may be white chaff rash, vitiligo, florid chaff rash, anemic nevus and so on. 1. white chaff rash: the cause is not clear, may be related to Malassezia furfur, but malnutrition, often exposure to the sun, the use of irritating lotion, dry skin and so on can induce disease. 2. Vitiligo: it is due to melanocyte destruction leading to white patches on the skin, the cause of which is related to autoimmune system diseases, genetic factors, neurochemicals, and so on, and timely to the hospital dermatology department for treatment. 3. florid chaff rash: commonly known as sweat patches, manifested as skin spots, with scales on the surface, the skin may be white. 4. Anemic nevus: it is congenital skin vascular tissue development abnormality leading to skin hypopigmentation, appearing skin irregular pale color patches. Children with white spots on the arm may also be related to other causes, try to take the child to the hospital for examination, identify the specific disease and timely treatment.