Pityriasis Rosea

Overview – Pityriasis Rosea

Pityriasis rosea is a self-limiting, post-viral exanthem that typically affects adolescents and young adults. It begins with a distinctive “herald patch” followed by the development of multiple scaly, oval red plaques, primarily on the trunk. Often confused with tinea or psoriasis, pityriasis rosea is benign, non-contagious, and typically resolves within 6–12 weeks. Recognition of its classic distribution and course is key for clinical diagnosis and reassurance.

Aetiology

• Likely a viral aetiology
• Often follows an upper respiratory tract infection

Epidemiology

• Most common in teenagers and young adults
• Occurs sporadically; not typically seasonal
• No gender predilection

Pathophysiology

• Strongly associated with reactivation of HHV-6 or HHV-7
  • These same viruses cause roseola infantum
• Occasionally triggered by influenza viruses or even vaccines

Clinical Features

Herald Patch

• First sign of the rash; appears 1–20 days before the generalised eruption
• Oval, pink-red plaque, typically on the trunk
• Measures 2–5 cm in diameter
• Often has a fine collarette of scale

Secondary Eruption

• Appears several days after the herald patch
• Multiple oval, red, scaly plaques develop
• Distribution is often along Langer’s lines → “Christmas tree” pattern on back
• Commonly affects:
  • Chest and back
  • Thighs, neck, and upper arms
• Lesions may be mildly itchy or asymptomatic

Duration

• Typically lasts 6–12 weeks
• May leave temporary post-inflammatory pigmentation

Management

• Reassurance is key – it is self-limiting and non-contagious
• Supportive care:
  • Plain water baths or soap substitutes (e.g. bath oils, aqueous cream)
  • Emollients for dry or itchy skin
  • Sun exposure may help resolution
• If symptomatic:
  • Topical corticosteroids to reduce itch
  • Oral antihistamines for pruritus
  • Acyclovir may reduce disease duration if given early
  • Phototherapy in extensive or resistant cases

Summary – Pityriasis Rosea

Pityriasis rosea is a benign, self-resolving skin condition caused by viral reactivation, typically seen in young adults. It starts with a herald patch followed by a widespread, scaly rash that follows a characteristic distribution. Treatment is mainly supportive, with topical steroids and antivirals used in symptomatic cases. For a broader context, see our Skin & Dermatology Overview page.