Pityriasis rosea is a characteristic skin condition, which commonly affects people between the ages of 10 and 35, but may occur at any age. The rash usually lasts from several weeks to several months.
Pityriasis rosea often begins with a single large, scaly, pink patch on the trunk, called a “herald” patch.
A widespread rash usually follows one to two weeks later. The rash occurs on the trunk, limbs and neck, but rarely involves the face. The typical rash consists of small, oval pink to brown scaly patches arrange along the skin creases, giving an appearance of a ‘Christmas tree’ on the back.
They come up in crops, at intervals of a few days for the first one to two weeks. The rash is itchy in about half of the affected patients. It usually fades and disappears within six to eight weeks, but can sometimes last much longer. The patient is often otherwise well throughout the course of the rash.
The rash will usually fade without leaving marks but they may leave light or dark patches in people with dark skin, but these marks will also eventually fade.
The cause is unknown, but there is recent evidence suggesting a virus to be the cause. Pityriasis rosea is, however, not contagious. Interestingly, the rash usually occurs only once in a lifetime
The dermatologist makes the diagnosis, through identifying the characteristic appearance of the rash and its clinical course. The diagnosis can sometimes be difficult and investigations such as skin scrapings for fungal elements, blood tests or a skin biopsy may be ordered to exclude other conditions with similar looking rashes.
Pityriasis rosea often requires no treatment and it usually goes away by itself. Oral or topical medications may be required if the associated itch is intense or bothersome.