I Have White Splotches on My Arm After the Sun

White splotches on the skin are typically an indication of loss of pigment. After sun exposure, the skin darkens as skin cells produce increased levels of the melanin pigment. Loss of pigment in a few patches of skin creates white spots that can be alarming to find on one's arm. The best way to determine the reason behind the loss of pigment is to see a dermatologist to determine the cause of this skin affliction.

Yeast

• One common cause of white spots on the skin after sun exposure is tinea versicolor yeast. This yeast is found naturally in the environment, but certain people are more susceptible to contracting it in the form of white spots; people with oily skin and pregnant women, for example, are particularly vulnerable. The yeast prevents underlying skin from tanning, leaving uneven white patches on the skin. Versicolor yeast is not contagious and can be treated by applying a cream designed to combat athlete's foot or jock itch.

Vitiligo

• Vitiligo, also known as leucoderma, is a rare skin disorder that causes patches of skin to slowly lose pigmentation. The loss of melanin pigmentation leaves behind white patches on the skin. There is no known cause of vitiligo, but some suspected causes include stress, heredity and sunburns. After diagnosis by a dermatologist or general physician, vitiligo is usually treated with medication, surgery or adjunctive therapy.

Nevus Depigmentosus

• Nevus Dipigmentosus is another skin disorder in which pigment is lost. This disorder is usually present at birth, but grows more prominent as the afflicted child matures. Low production of skin pigment and abnormal melanocyte cell functioning are the causes of the white patches on the skin, which can be exacerbated after sun exposure when the skin surrounding the patches turns darker. These lesions can sometimes be treated with laser and grafting techniques.

Other Conditions

• Skin injury is occasionally the cause of white splotches on the skin after sun exposure. Skin damage like that due to a burn or acne inflammation can damage pigment-producing melanocyte cells. Once damaged, these cells may cease to produce pigment indefinitely. Other causes of white spots on the skin include pityriasis alba, which is a chronic skin disorder that affects children in the winter, and idiopathic guttate hypomelanosis, which is a genetic disorder associated with aging that produces small white spots on the face.