Pityriasis Rosea ICD-10: L42

Acute self-limiting skin condition / Viral-associated rash

Often searched as: rash on chest and back, oval patch then spreading rash, Christmas tree rash, herald patch skin, pink rash on torso, rash that spreads after one big spot, scaly rash on trunk, rash that started with one oval patch…

Clinical urgency level

lowmediumhigh

Systems Affected

skin

Severity Levels

mild

Classic presentation with herald patch followed by Christmas tree rash, mild itch, resolving within 6–8 weeks — supportive care only.

moderate

Extensive rash with significant itch, papular or vesicular variant, or prolonged course beyond 8 weeks — requires treatment for symptom relief.

severe

Pityriasis rosea during pregnancy (associated with premature delivery and fetal complications in the first 15 weeks) — requires urgent obstetric and dermatologic evaluation.

Red Flags

Rash appearing during pregnancy — especially in the first trimester (risk of fetal loss or premature birth)
Rash persisting beyond 3 months without improvement
Herald patch followed by rash that doesn't match the Christmas tree pattern — consider secondary syphilis
Widespread painful or vesicular lesions
Systemic symptoms (fever, joint pain, severe fatigue) alongside the rash
Rash in an immunocompromised patient

Clinical Presentation

Pityriasis rosea — herald patch (large oval) and smaller satellite lesions in Christmas tree pattern on the back

Source: Wikimedia Commons (CC BY-SA 3.0 )

Pityriasis rosea image gallery — DermNet NZ

View gallery on DermNet NZ (image gallery reference)

When to See a Doctor

See a doctor if you develop a large oval scaly patch on your trunk followed 1–2 weeks later by a spreading rash, especially if you're pregnant. Pityriasis rosea during early pregnancy is a medical concern. Also seek evaluation if the rash looks unusual, is very painful, or doesn't start improving after 6–8 weeks — secondary syphilis can look identical and must be ruled out.

Differential Diagnosis

Secondary syphilis (most important — identical rash, involves palms and soles, positive serology)
Tinea corporis (ringworm — circular, responds to antifungal)
Guttate psoriasis (teardrop-shaped, silvery scale, often post-strep)
Nummular eczema (coin-shaped, itchier, no herald patch)
Drug reaction (lichenoid or maculopapular — medication history key)
Pityriasis versicolor (more persistent, fungal)

Comorbidities

HHV-6 and HHV-7 reactivation (proposed viral trigger)
Recent upper respiratory infection (common preceding event)
Pregnancy (associated with adverse fetal outcomes in early-onset cases)

Prognosis

Pityriasis rosea is self-limiting and resolves completely in 6–8 weeks in most patients without any treatment. Post-inflammatory hyperpigmentation may persist for weeks after the rash fades, particularly in darker skin tones. Recurrence is rare (less than 2%). Symptomatic treatment with antihistamines, topical corticosteroids, or phototherapy can reduce itch and duration. No scarring or long-term skin changes occur.

Detailed Overview

Causes, Symptoms, and When to Take Action Pityriasis rosea, also known as pink lichen, is an acute, self-limiting skin condition that typically begins with a single herald patch, followed by a widespread rash. It is generally benign and resolves on its own. How It Looks Texture: Slightly scaly or papulosquamous lesions Color: Pink or rose-colored patches Shape: Begins as a single oval herald patch, followed 1 to 2 weeks later by multiple smaller oval patches in a characteristic 'Christmas tree' pattern on the trunk and proximal limbs Location: Most commonly appears on the trunk and upper arms or legs Why Does It Appear? The exact cause remains unclear. It may be prompted by viral reactivation or an unidentified environmental trigger. The condition is not considered contagious and often resolves on its own. Should You Be Concerned? Pityriasis rosea is generally harmless and usually resolves within 6 to 8 weeks. However, it's advisable to see a healthcare provider if the rash persists beyond three months, lesions are painful or infected, or it appears during pregnancy. Can You Prevent It? There is no known way to prevent pityriasis rosea. Supportive care and symptom relief are the main approaches. 👉 How Piel AI Can Help Piel AI allows you to track images of your rash over time. While it does not diagnose, it can help monitor the progression and support conversations with your healthcare provider. Summary Pityriasis rosea is an acute, self-resolving skin rash starting with a herald patch and followed by a distinctive spread of rose-colored lesions. The cause is unknown, and it's not contagious. It typically lasts 6–8 weeks and resolves without treatment. Medical evaluation is recommended if the rash persists or is atypical.

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