Review question

We reviewed the evidence for the effect of any treatment on the common viral skin infection molluscum contagiosum. We excluded people with a repressed immune system or sexually transmitted molluscum contagiosum.

Background

Molluscum contagiosum in healthy people is a self limiting, relatively harmless viral skin infection. It mainly affects children and adolescents and is rare in adults. It occurs worldwide, but seems much more frequent in geographic areas with warm climates. Molluscum contagiosum usually presents as single or multiple pimples filled with an oily substance. People may seek treatment for social and cosmetic reasons and because of concerns about spreading the disease to others. Treatment is intended to speed up the healing process.

Study characteristics

We searched the literature to July 2016. We included 22 trials (total of 1650 participants). Twenty of the studies evaluated topical treatment, and two studies evaluated treatment taken by mouth (oral). Comparisons included physical therapies, as well as topical and oral treatments. Most studies were set in hospital outpatient or emergency departments, and were performed in North America, the UK, Asia, or South America. Participants were of both sexes and were mainly children or young adults. Follow-up duration varied from 3 to 28 weeks after randomisation. Only five studies had longer than 3 months’ follow-up.

Five studies reported commercial funding, three studies obtained medication for free from pharmaceutical companies, 12 studies did not mention the source of funding, one study reported charity funding, and one study reported they had had no financial support.

Key results

We found that many common treatments for molluscum, such as physical destruction, have not been adequately evaluated. Some of the included treatments are not part of standard practice.

We found moderate-quality evidence that topical 5% imiquimod is probably no more effective than vehicle (i.e. the same cream but without imiquimod) in achieving short-, medium-, and long-term clinical cure. High-quality (and thus more certain) evidence showed that topical 5% imiquimod is no better than placebo at improving molluscum up to three months after the start of treatment.

High-quality evidence showed that 5% imiquimod differed little or not at all in the number of side effects compared to vehicle. However, moderate-quality evidence suggests that there are probably more application site reactions when using topical 5% imiquimod compared with vehicle.

Low-quality evidence, based on one or two mostly small studies, revealed the following results for the outcome short-term clinical cure: 5% imiquimod less effective than cryospray or 10% potassium hydroxide; 10% Australian lemon myrtle oil more effective than olive oil; 10% benzoyl peroxide cream more effective than 0.05% tretinoin; 5% sodium nitrite co-applied with 5% salicylic acid more effective than 5% salicylic acid alone; and iodine plus tea tree oil more effective than tea tree oil or iodine alone. We found more uncertain (low-quality) evidence to suggest that 10% potassium hydroxide is more effective than saline; homeopathic calcarea carbonica is more effective than placebo; 2.5% solution of potassium hydroxide is less effective than 5% solution of potassium hydroxide; and 10% povidone iodine solution and 50% salicylic acid plaster are more effective than salicylic acid plaster alone.

Except for the severe application site reactions of imiquimod, none of these treatments led to serious adverse effects (low-quality evidence). Pain during treatment application, redness, and itching were among the most reported adverse effects.

We found no differences between the treatments assessed in the other comparisons.

We found no randomised trials for several commonly used treatments, such as expressing lesions with an orange stick or topical hydrogen peroxide. Since most lesions resolve within months, unless better evidence for the superiority of active treatments emerges, molluscum contagiosum can be left to heal naturally.

Quality of the evidence

For topical imiquimod, the quality of the evidence for clinical cure, short-term improvement, and adverse effects was moderate to high. For all other comparisons, the quality of the evidence for short-term clinical cure and adverse effects was low. Common limitations of the included studies were that the numbers of participants were small, the investigators were not blinded, and participants who did not complete the study (numerous in some studies) were not included in the analyses.

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