Interventions for pityriasis rosea, skin rash of unknown cause

Pityriasis rosea is a scaly rash that mostly affects young adults. It is relatively common and affects about 170 out of every 100,000 people in the community each year. The first sign is a patch of scales, usually on the trunk. A generalised eruption then follows and all lesions disappear within 2 to 12 weeks. This review is important because about 50% of people with pityriasis rosea experience moderate to severe itch. It is not known whether the current treatments, which include tablets, creams, and ultra-violet radiation, are useful and whether the benefits outweigh the risk of adverse effects.

We found three randomised controlled trials involving 148 participants. One small poor quality trial compared liquorice root with an anaesthetic injected intravenously (23 people), a fair quality trial compared an antihistamine with a steroid taken orally (85 people), and a good quality trial that compared an antibiotic with placebo tablets (40 people).

The poor quality trial found no significant difference between liquorice root and anaesthetic for resolving symptoms or rash. The fair quality trial found no significant difference in itch resolution between the antihistamine and the steroid. However the antihistamine and the steroid on their own were both found to be better at clearing rash than a combination of antihistamine and steroid. The small good quality trial found that the oral antibiotic erythromycin was better than placebo in improving the rash and decreasing the amount of itching.

No serious adverse effects were reported for any intervention. Two out of 17 people on oral erythromycin and 1 out of 17 people on oral placebo reported minor gastrointestinal upset.

We conclude that there is inadequate evidence of efficacy for most treatments but oral erythromycin may be effective in treating the rash and relieving the itch.

Limitations of this review include the small number of trials identified, the small number of participants involved, the inadequate methodology of two of the studies, and finding only one small study that reported the clinical benefits of oral erythromycin.

Authors' conclusions: 

We found inadequate evidence for efficacy for most treatments for pityriasis rosea. Oral erythromycin may be effective in treating the rash and decreasing the itch. However, this result should be treated with caution since it comes from only one small RCT. More research is necessary to evaluate the efficacy of erythromycin and other treatments.

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Background: 

Pityriasis rosea is a scaly rash that mainly affects young adults. It can be very itchy but most people recover within 2 to 12 weeks.

Objectives: 

To assess the effects of interventions for pityriasis rosea.

Search strategy: 

We searched the Cochrane Skin Group Specialised Register (December 2004), the Cochrane Central Register of Controlled Clinical Trials in The Cochrane Library (Issue 4, 2004), MEDLINE (1966 to January 2005), EMBASE (1976 to January 2005), LILACS (1982 to January 2005), BIOSIS Preview (1980 to June 2002), and ongoing trials databases. We scanned bibliographies of published studies, abstracts from dermatology conference proceedings, corresponded with trialists and contacted the pharmaceutical industry.

Selection criteria: 

Randomised controlled trials evaluating interventions for pityriasis rosea.

Data collection and analysis: 

Two authors independently assessed trial quality and extracted data. We contacted study authors to retrieve missing data.

Main results: 

Three trials involving 148 people were included. One poor quality trial (23 people), compared intravenous glycyrrhizin and intravenous procaine. It found no significant difference between the two interventions for treating symptoms and rash.

One fair quality trial (85 people), compared the oral antihistamine dexchlorpheniramine (4 mg), the oral steroid betamethasone (500 mcg), and a combination of betamethasone (250 mcg) and dexchlorpheniramine (2 mg). It found no significant difference in itch resolution at two weeks, as rated by the participants, between dexchlorpheniramine and betamethasone, and the combination of dexchlorpheniramine and betamethasone. However, both dexchlorpheniramine and betamethasone alone seem to be better at clearing rash than the combination of dexchlorpheniramine and betamethasone. These interventions were not compared with placebo.

The small good quality trial (40 people) that compared oral erythromycin and placebo found that erythromycin was more effective than placebo in terms of rash improvement, as rated by the trialists, after two weeks (RR 13.00; 95% CI 1.91 to 88.64). It was also more effective in decreasing the itch score (difference of 3.95 points, 95% CI 3.37 to 4.53).

No serious adverse effects were reported for the interventions. Two out of 17 people on oral erythromycin and 1 out of 17 on placebo reported minor gastrointestinal upset.

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