Pityriasis alba

Pityriasis alba is common. It is a mild form of dermatitis in which postinflammatory hypopigmentation is marked. Poorly defined hypopigmented and minimally scaly patches appear on the face and upper arms. Patches are most obvious in summer when the surrounding skin is tanned. For a photo of pityriasis alba, see here. Affected areas are often asymptomatic, but can be mildly itchy. It is more common in patients with atopic dermatitis, and is mainly seen in prepubertal children (particularly those with darker skin types).

Pityriasis alba must be differentiated from:

• vitiligo, which has sharply demarcated areas of complete depigmentation and no scale
• pityriasis versicolor, which rarely occurs in prepubertal children and rarely affects the face.

Avoid contact with skin irritants (eg soap, shampoo). Use a soap substitute, and apply an emollient twice daily (for more information on emollients, see improving skin condition). This is sufficient therapy for many patients. If inflammation is present, use:

The affected skin does not repigment until the scaliness has resolved—advise the patient to continue to use emollients to keep the skin moisturised.