Pityriasis rosea

This rash of unknown origin can last up to 12 weeks and then resolves spontaneously. It usually affects teenagers and young adults. It may be slightly itchy and scaly but is otherwise asymptomatic. It is sometimes preceded by a generalised viral infection.

The presentation of pityriasis rosea develops over time starting with a single oval patch called a herald patch. This is usually 2–5 cm in diameter and precedes the rest of the rash by up to 20 days. Characteristically, it has a slightly scaly trailing edge; this describes the edge just inside the patch. After the herald patch the rest of the lesions, which are similar although usually smaller, appear mainly over the trunk but also affecting the arms and legs. The distribution of these lesions is often compared to a fir tree, in that they follow the lines of the ribs around the trunk. Lesions do not usually appear on the face.

Nursing care will centre around helping to reassure the patient that what they have is self-limiting and non-contagious. Patients may have been wrongly diagnosed with either psoriasis or tinea corporis and it should be clarified that pityriasis rosea is not related to either of these conditions. Good skin care such as washing with a soap substitute and using a topical emollient may be helpful especially if the skin is itchy. For particularly itchy skin, a brief course of topical steroids (moderate potency) may provide some relief. However, it is unlikely to make any difference to the course of the condition.