Pityriasis Alba

Non-scarring hypopigmented dermatosis characterized by ill-defined hypopigmented macules or patches with fine scaling

Etiology & Pathophysiology

The exact cause is unknown, but several mechanisms are proposed:

Subclinical dermatitis

Mild inflammation temporarily reduces melanocyte activity → decreased melanin production → hypopigmentation.

Predisposing factors

Factor
Mechanism
Xerosis (dry skin)
Triggers low-grade inflammation & scaling
Sun exposure
Darkens surrounding skin, accentuating hypopigmented areas
Atopy (AD, asthma, allergic rhinitis)
Increased skin sensitivity & inflammation
Irritants/overwashing
Disrupts epidermal barrier

Barrier dysfunction

Epidermal barrier impairment → increased TEWL → inflammation → mild hypomelanosis.

Epidemiology

  • Common in children and adolescents (3–16 years)
  • More noticeable in darker skin phototypes
  • Frequently associated with atopic individuals
  • Higher prevalence in warm and humid climates → associated with UV rays

Clinical presentation

  • Hypopigmented macules/patches with ill-defined borders
  • Fine scaling, sometimes barely visible
  • Mild pruritus may be present during inflammatory phase
  • Size varies from 0.5–5 cm or more
  • Multiple lesions, sometimes solitary
notion image
  • Common sites:
    • Face (especially cheeks), forehead
    • Upper arms
    • Neck and upper trunk

Investigations

Mainly clinical.
Additional tests (rarely required)
Test
Findings
Wood’s lamp
Non-fluorescent hypopigmentation
KOH
Negative (rule out tinea versicolor)
Histopathology (if done)
Mild spongiosis, hyperkeratosis, reduced melanin

Management

Generally self-limiting, often resolves within months to years.
Treatment principles
  1. Patient & parent education
      • Benign, not contagious
      • Repigmentation occurs gradually
  1. Skin barrier restoration
      • Regular emollients/moisturizers (2–3 times daily)
      • Avoid harsh soaps and irritants
  1. Topical medications (if needed)
      • Low-potency topical corticosteroids (e.g., hydrocortisone 1%-2.5%) for inflammatory phase
      • Calcineurin inhibitors (tacrolimus 0.1%/pimecrolimus 1%) as steroid-sparing options, especially on the face
  1. Photoprotection
      • Use sunscreen ≥ SPF 30
      • Reduces contrast with surrounding skin