Many kinds of diseases can appear white spots on the arms, need to go to the hospital by the dermatologist check, and through the dermoscope, Wood’s lamp and other checks to identify, common causes are vitiligo, pityriasis and white furuncle, etc. 1, vitiligo: is pigment loss skin mucous membrane disease, any part of the skin can occur. The white spots are flat with the skin, no obvious bumps and depressions when touched by hand, and the color is porcelain white change, while the skin around the white spots is slightly darker. If not treated, the white spots may appear to spread and spread, and the patient can follow the medical advice of topical corticosteroid medication for relief; 2. Pityriasis pilaris: also known as sweat spots, is caused by Malassezia infection. It can be brown, light brown, light red, light yellow or white, with a small amount of furfuraceous scales on the surface, which is manifested as flower-like white spots, and the phenomenon of florid moss is easy to spread and affect the beauty. If not treated can last for several years, patients should use antifungal drugs for treatment under the guidance of professional doctors; 3, white furuncle: also known as simple furuncle. White spots are round or oval, varying in size, with slightly clear borders, covered with a small amount of fine furfuraceous scales on the surface, and the white spots have a mild roughness when touched by hand. Scattered flakes can be seen on the surface, mostly related to the body’s trace elements or vitamin deficiency, malnutrition, sun exposure, etc. White furuncle can fade by itself, generally no need to treat, should avoid excessive cleaning; 4, other: anemic nevus, anaplastic nevus, seborrheic dermatitis and other diseases can also lead to patients with white spots on the arms. The congenital diseases such as anemic nevus and pigmentless nevus may need to be identified with vitiligo through Wooden lamp and other examinations, which can be observed and not dealt with for the time being. The actual fact is that you can use antihistamines and topical glucocorticoids to treat seborrheic dermatitis.