Pityriasis alba is a condition in which there are round, light patches of skin covered in fine scales. Most commonly found in children, the patches can occur on any part of the body, but are most noticeable on the face and upper arms. The white patches are the result of mild eczema and the loss of color is only temporary. Pityriasis rosca is a rash that occurs most commonly in people between the ages of 10 and 35, but may occur at any age. The rash can last from several weeks to several months.