Pityriasis rosea (PR) is a red, scaly rash which lasts about 12 weeks. It is characterized by a “herald patch” which is followed by multiple similar, but smaller, oval red patches. The rash of pityriasis rosea is located primarily on the chest and back. Most frequently, pityriasis rosea affects teenagers and young adults, but in can affect individuals of nearly any age. Pityriasis rosea affects both males and females.
Pityriasis rosea begins with a “herald patch”, which is a single, oval, pink or red plaque (1-3 inches in diameter) with slight scale just inside the edge of the lesion. A few days after the appearance of the “herald patch,” additional scaly spots appear on the chest and back similar to the herald patch, but smaller in size. A few spots may also appear on the neck, upper arms, and thighs, but involvement of the face or scalp is uncommon. Pityriasis rosea plaques usually follow the relaxed skin tension lines on the upper trunk and are often described as “looking like a Christmas tree”. PR is normally asymptomatic, although it may occasionally be itchy.
Pityriasis rosea is associated with reactivation of herpesviruses 6 and 7 (which cause the rash called roseola in infants). Viral infections such an upper respiratory infection, vaccines, and medications can trigger pityriasis rosea to develop, but many patients are often asymptomatic. Second attacks of pityriasis rosea are uncommon (1–3%), but may occur years later.
Pityriasis rosea is self-limited and resolves without therapy in a few months. As a result, most people do not need any treatment. A moisturizer can be beneficial is the skin is itchy or sore. Likewise, oral antihistamine tablets may help with itching. A topical corticosteroid medication may help control itching and slightly shorten the course of this eruption. Finally, systemic corticosteroids, certain antiviral medications, such as acyclovir and famciclovir, and certain oral antibiotics, such as erythromycin, may shorten the duration of the rash associated with pityriasis rosea.