From the Research
Pityriasis rosea is believed to be triggered by viral infections, particularly human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7), as suggested by the most recent and highest quality study 1. The condition typically begins with a single, larger "herald patch" followed by a widespread rash of smaller, oval-shaped, scaly patches that often follow skin lines in a "Christmas tree" pattern. Key characteristics of pityriasis rosea include:
- A common, acute, self-limited papulosquamous dermatosis that primarily affects children and young adults
- Occurs mainly in individuals between 10 and 35 years of age with a peak during adolescence
- A mild prodrome consisting of headaches, fever, malaise, fatigue, anorexia, sore throat, enlarged lymph nodes and arthralgia is present in about 5% of patients
- The most common presenting sign, found in approximately 80% of patients, is a "herald" or "mother" patch which is larger and more noticeable than the lesions of the later eruption
- A generalized, bilateral, symmetrical eruption develops in approximately 4 to 14 days and continues to erupt in crops over the next 12 to 21 days
- Typical lesions are 0.5 to 1 cm, oval or elliptical, dull pink or salmon-colored macules with a delicate collarette of scales at the periphery
- The long axes tend to be oriented along the skin lines of cleavage (Langer lines)
- Lesions on the back may have a characteristic "Christmas tree", whereas lesions on the upper chest may have a V-shaped pattern The condition is not contagious through direct contact and usually resolves on its own within 6-8 weeks without specific treatment. While the viral theory is most accepted, some cases may be related to medication reactions, stress, or immune system responses. No laboratory test can definitively diagnose pityriasis rosea, and treatment focuses on symptom management rather than addressing the underlying cause, as noted in 1.