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The dearth of evidence regarding treatments for non-genital molluscum contagiosum leaves physicians uncertain if any interventions work better than allowing the infection to resolve itself, according to researchers.

"The overall conclusions have hardly changed. We found no strong evidence either for or against the most commonly used treatment options for molluscum contagiosum. Allowing for natural resolution of the infection remains a reasonable approach," wrote Johannes C. van der Wouden, PhD, the Amsterdam Public Health Research Institute, and colleagues in a in JAMA Dermatology.

"We found some evidence to suggest that 10% potassium hydroxide is more effective than saline; 5% solution of potassium hydroxide is favored compared to 2.5% solution of potassium hydroxide; 10% povidone iodine solution plus 50% salicylic acid plaster is favored compared to salicylic acid plaster alone; and homeopathic calcarea carbonica is favored compared to placebo."

In patients without immune deficiency, resolution of molluscum contagiosum can take several months, or in extreme cases, 3 to 4 years, van der Wouden et al noted, adding, however, that patients may desire treatment for social or cosmetic reasons, or to avoid scratching or spreading the infection.

Updating a 2009 review, the authors searched the Cochrane Skin Group Specialized Register, Central, Medline, Lilacs, and Embase through July 2016. They also searched six trial registries, scoured the included studies for additional relevant references and queried pharmaceutical companies and experts to identify further relevant randomized controlled trials. The search identified 11 new studies, making an evaluable pool of 22 studies with a total of 1,650 participants.

Among the 11 new studies were four never-published randomized controlled trials of imiquimod, which collectively provided moderate-quality evidence for lack of effect of 5% imiquimod compared with placebo in the short, medium, and long term. Pooling the results of the four unpublished studies with a total of 544 patients and treatment times between 8 and 16 weeks showed a clinical cure rate of 14.5% (79 patients) for imiquimod, versus 11.8% (36 patients) for placebo (pooled risk difference: 4%; 95% CI: -1% to 8%).

There were similar but more certain results for short-term improvement (four studies, 850 participants, 12 weeks after starting treatment, risk ratio 1.14; 95% CI: 0.89-1.47; high-quality evidence). The same four studies showed that after 12 weeks, the RR for complete clearance was 1.33 (95% CI: 0.92-1.93). At 28 weeks, two studies with 702 subjects showed that the RR of complete clearance was 0.97 (95% CI: 0.79-1.17).

"We can provide no reliable evidence-based recommendations for the treatment of molluscum contagiosum at present, except for 5% imiquimod, which based on moderate-quality evidence from three unpublished studies is probably no more effective in terms of clinical cure than its vehicle but is probably more harmful in terms of application-site reactions," the authors wrote.

High-quality evidence from three studies with 827 participants showed an RR of 0.97 for topical imiquimod versus vehicle, but pooled RR for application-site reactions in imiquimod-treated cohorts was 1.41 (95% CI 1.13-1.77).

Based on the high-quality evidence, the authors said that topical 5% imiquimod is no more effective than its vehicle in providing short-term improvement. Likewise, long-term clinical cure rates were 38.3% for imiquimod versus 39.7% for placebo (pooled risk difference, 1%; 95% CI -9% to 6%).

The remaining publications reviewed in the analysis involved small trials that pitted one therapy against another, often without a placebo comparator. There was limited, low-quality evidence from 11 comparisons for short-term cure efficacy of treatments including cryospray and potassium compared with imiquimod, of benzoyl peroxide 10% compared with 0.05% tretinoin, and tea tree oil plus iodine versus tea tree oil or iodine alone.

Van der Wouden and colleagues wrote that the small studies reporting no differences might have produced clinically relevant differences if treatments were evaluated in larger samples. The team also said they could not guarantee that they did not miss relevant research; one relevant study was ongoing at the time of publication, and the authors were still attempting to classify and evaluate several others, they said.

This article originally appeared on the website of our partner Dermatology Times, which is a part of UBM Medica. (Free registration is required.)

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