Pityriasis Alba is a chronic skin disorder that affects some children usually between the ages of 6 to 12. This rash is characterized by patches of lighter skin mainly on the face, although the neck, upper chest, and arms are sometimes involved. The borders of the rash are not clearly visible. The light colored patch seems to blend gradually into normal appearing skin. Sometimes the rash is covered by very fine skin flakes resembling a light dust.
Cause of Pityriasis Alba
The cause of pityriasis alba is unknown. The rash appears to get worse when the skin is dry. It is often thought of as a mild form or eczema. In the winter months when the skin is drier, the rash may be flakier. Pityriasis alba is most noticeable in the summertime when the surrounding skin gets tanner, because it remains the same color.
Sometimes pityriasis alba is confused with tinea versicolor, which is an autoimmune response to a fungus on the skin. The diagnosis of tinea versicolor can be ruled out by a KOH examination of the flakes. In this examination, a small amount of the surface flakes are scraped off the skin onto a glass slide. KOH is added to the scraping and the slide is viewed under the microscope. Fungal elements can be seen under the microscope with tinea versicolor but not with pityriasis alba.
Pityriasis alba can also be confused with vitiligo. Pityriasis alba can be distinguished from vitiligo by the border of the rash. The rash of vitiligo has a very distinct border with a sharp line between normal and lighter-colored skin.
Treatment of the rash is not necessary since it will resolve on its own. Using a moisturizer or hydrocortisone may make the patches go away faster. However, even with treatment, the rash may take months to resolve.