How to Recognize Pityriasis Rosea

Pityriasis rosea is a common, itchy rash that resolves on its own. The rash begins with a herald patch, pictured here. The herald patch is a single 2 to 10 centimeter round or oval-shaped lesion that most often appears on the trunk and resembles ​ringworm.

Within a few days, smaller lesions appear mainly on the trunk or wherever the herald patch is located, but they can also spread to the arms, legs, and face. Lesions can continue to spread several weeks after the herald patch first appeared.

This is another example of a herald patch at the onset of pityriasis rosea. A full rash usually develops within a few days or several weeks of the herald patch's appearance. Pityriasis rosea typically occurs in people between 10 and 35 years of age.

This is what pityriasis rosea looks like when the full rash has broken out. Lesions start to appear around the herald patch and can spread to the arms, legs, and face. The lesions tend to be oval-shaped with thin, tissue-like scales that cover them, and they can be itchy.

Lesions are salmon-colored and relatively discrete on light skin. On dark skin they are hyperpigmented.

Pityriasis rosea most often takes hold on the trunk. Studies that have investigated the skin condition's potential viral or bacterial origins are inconclusive, and the cause for pityriasis rosea is unknown.

Pityriasis rosea tends to occur most often in colder months, and it occurs in all ethnicities. Only 2 percent of those who have had pityriasis rosea will have a recurrence.

Pityriasis rosea rashes tend to look the same, but an atypical rash is not uncommon. The photo above is an atypical form of pityriasis rosea. The lesions are not as distinct; instead, they are more generalized over the area.

The rash can be more papular, or bumpy, in young children, pregnant women and on darker skin tones. In infants vesicles, and wheals have been known to appear. Even oral lesions can occur, and in some cases, the rash covers the entire body.

This is an atypical pityriasis rosea rash on the upper back. Normally there are fewer lesions that are more spread out over the trunk, but these papular lesions cover a lot of the area and are very close together.

If the rash can't be accurately diagnosed solely on appearance, a KOH (potassium hydroxide) test will be done to identify the rash's fungal elements.

Although pityriasis rosea appears mostly on the trunk, it's not uncommon for it to spread around the body, including the arms, neck and even scalp. The rash rarely spreads to the face. It's unknown whether pityriasis rosea is contagious and there is no cure. The skin condition runs its course and usually clears up after 6 to 8 weeks.

In many cases, a dermatologist will prescribe an oral antihistamine or topical steroids to help with itching. Few studies have investigated treatment options, but there are few theories that may shorten the rash's course, including concentrated doses of erythromycin (an antibiotic used to treat acne), sun exposure and UVB therapy.