White spots in the arms are indicative of a fungal infection, named Tinea versicolor. It is affected by genetic factors. Treatment takes time. It is similar to ringworm infection. It is more obvious, especially in the summer. It is commonly seen to occur in adolescents and adults up to 30 years of age. Causative factors are tight fitting garments, steroid consumption, chronic conditions and excessive perspiration. It seems to reduce during the course of winter.
Pityriasis alba is another skin infection resulting in spots. The skin becomes lighter, due to reduced pigmentation. Soaps are better avoided, as they deprive you of your pigmentation. Creams with steroids are helpful. Face wash is useful. Moisturizers are also equally effective. A healthy and balanced diet is important. Pityriasis alba is accompanied by white scaly patches. Exposure to sun results in uneven patches, which are oval or circular. It is of one to two inches diameter and is commonly seen on the neck, face, upper arms and upper trunk. It is a mild type of eczema or skin disorder, accompanied by itching and inflammation. Sunscreen usage helps in reducing the patches, thereby reducing the spots. Livido reticularis is yet another skin infection caused by improper circulation.
answered by Dr C