Pityriasis rosea (PR) is a common non-cancerous (benign) rash that mostly affects the back, chest, and abdomen. It starts fairly quickly, lasts about 6–8 weeks, and is usually not itchy.
The cause of pityriasis rosea is not known, though it may be caused by infection with an unknown virus.
Who's At Risk
Pityriasis rosea can occur in people of any age, any race, and either sex, but it is most common in teenagers and young adults (10–40 years old).
Signs and Symptoms
The most common locations for pityriasis rosea include:
- Upper back
- Upper arms
In an uncommon type of pityriasis rosea, the rash may be concentrated in the armpits and groin or on the face, forearms, and shins. Pityriasis rosea usually begins with a single patch of pink-to-red, scaly skin, from 2–5 cm in size. This "herald patch" is usually located on the trunk, neck, or upper arms. The herald patch is followed 1–3 weeks later by the development of a widespread rash, with smaller (0.5–2 cm) oval patches of pink-to-red, scaly skin on the trunk and upper arms. The second rash forms a "Christmas tree" pattern on the back.
Some people report feeling mildly ill (headache, stuffy nose, muscle aches) for 1–2 weeks before the herald patch forms. Additionally, some people experience itching with pityriasis rosea. Becoming overheated by exercising or taking a hot shower may increase itching or make the rash more obvious.
Pityriasis rosea is a self-limited condition, meaning that it goes away on its own, typically within 6–8 weeks, without treatment. However, the rash often leaves behind patches of lighter (hypopigmented) or darker (hyperpigmented) skin, which are more obvious in darker-skinned people and may take months to return to its normal color.
The herald patch of pityriasis rosea may be mistaken for ringworm (tinea corporis), but over-the-counter antifungal creams do not improve it. Similarly, the herald patch may look like eczema, but over-the-counter hydrocortisone creams do not affect it. The second, widespread rash of pityriasis rosea will always develop even if the herald patch is treated.
Itching with pityriasis rosea can sometimes be reduced with:
- Oatmeal baths
- Lukewarm (rather than hot) baths and showers
- Anti-histamine pills
Other than relieving the itch, there are no self-care measures for pityriasis rosea. Although the rash should go away on its own within 6–8 weeks, see your doctor for evaluation of any widespread rash.
When to Seek Medical Care
If you develop a patch of pink, scaly skin that does not respond to over-the-counter anti-fungal creams or hydrocortisone cream, or if you develop a widespread rash, see a dermatologist or another physician for an evaluation.
Be prepared to discuss the following with your doctor:
- The course of the rash (when it started, whether or not there was a herald patch, etc)
- What treatments, if any, you have tried
- Whether or not any friends or relatives have a similar rash
- Your recent sexual history
- Your medication history (make sure you know the names of any pills you have taken within the last month)
Treatments Your Physician May Prescribe
Although most people have the classic form of pityriasis rosea, some individuals develop a form of pityriasis rosea with unusual (atypical) features. These atypical types of pityriasis rosea may be more difficult to diagnose and may require a skin biopsy.
This procedure involves:
- Numbing the skin with an injectable anesthetic.
- Sampling a small piece of skin by using a flexible razor blade, a scalpel, or a tiny cookie cutter (called a "punch biopsy"). If a punch biopsy is taken, a stitch (suture) or two may be placed and will need to be removed 6–14 days later.
- Having the skin sample examined under the microscope by a specially trained physician (dermatopathologist).
In addition, your physician may want to do blood tests for other medical conditions.
Because pityriasis rosea is benign and self-limited, no treatment is required. However, some people with pityriasis rosea have mild-to-severe itching, and your physician may suggest:
- Moisturizing creams or lotions
- Oatmeal baths
- Topical menthol-phenol lotions
- Topical corticosteroid (cortisone) creams or lotions
- Oral anti-histamine pills
- Ultraviolet light treatments
- Oral corticosteroid pills (if the pityriasis rosea is very severe)
Bolognia, Jean L., ed. Dermatology
, pp.158-160. New York: Mosby, 2003.
Freedberg, Irwin M., ed. Fitzpatrick's Dermatology in General Medicine
ed. pp.445-449. New York: McGraw-Hill, 2003.