NIHR DC Discover

NIHR Signal Molluscum contagiosum is best left to clear by itself

Published on 29 August 2017

doi: 10.3310/signal-000471

Molluscum contagiosum, the viral skin infection, is best left alone to heal by itself rather than being treated with medication, destructive treatments or creams. When comparing imiquimod (a skin cream that activates the immune system) with nothing, about 40% of people were clinically clear by 6 months in either group. Treatment increased the chance of severe adverse events such as irritation and scarring fourfold.

The majority of other treatment comparisons were from studies judged by the authors to be of low quality. Based on the findings from this study, clinicians should advise people who have a healthy immune system to leave molluscum contagiosum to clear by itself.

Considering the limited evidence on their effectiveness and risk of scarring even treatment for cosmetic reasons has uncertain evidence. Parents should be warned of the possibility of pain resulting from treatment of children.

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Why was this study needed?

Molluscum contagiosum is a viral skin infection and transmission occurs by close personal contact or via contaminated surfaces. The exact prevalence is unknown as many people do not seek medical attention but in a 2005 UK general practice-based survey of patient records, the annual incidence of new cases was 261 per 100,000 patients and 80% of cases are in children under 15.

It is generally a harmless condition that gets better within a few months without specific treatment but rarely, it can spread around the body and take up to 18 months or more to clear completely.

Treatment is often sought for cosmetic and social reasons or to prevent spread, however, the scientific basis for treatment is unclear and practitioners may be unsure whether to recommend treatment or not. The current study aimed to evaluate treatment options to see what worked if anything.

What did this study do?

This study reviewed 22 randomised controlled trials involving 1,650 participants - mostly children - with molluscum contagiosum. The trials compared 20 topical treatments (applied to the skin) and two oral treatments with either an alternative treatment or placebo in people who were not immunocompromised. Follow-up ranged from three to 28 weeks after randomisation. Only five studies had follow-up longer than three months.

The main outcome was a short-term clinical cure (up to three months after treatment start), shown by complete clearance of lesions.

Quality of evidence overall was judged to be low as most studies had small sample sizes and many had a high drop-out rate. The control comparison group was often an alternative treatment rather than a placebo, which may have shown some treatment effect which makes the overall effectiveness difficult to judge.

What did it find?

For 5% imiquimod cream compared to placebo:

  • Moderate-quality evidence showed a lack of effect for clinical cure either in the short-term (relative risk [RR] 1.33, 95% confidence interval [CI] 0.92 to 1.95; 4 studies, 850 participants), medium-term (RR 0.88, 95% CI 0.67 to 1.14; 2 studies, 702 participants) or long-term (RR 0.97, 95% CI 0.79 to 1.17; 2 studies, 702 participants). High-quality evidence showed no difference in short-term improvements (RR 1.14, 95% CI 0.89 to 1.47, 4 studies, 850 participants). The clearance at six months was about 40% in either group.
  • Moderate-quality evidence showed application site reactions were more frequent (RR 1.41, 95% confidence interval [CI] 1.13 to 1.77), including severe application site reactions (RR 4.33, 95% CI 1.16 to 16.19).

There were 11 comparisons between different treatments with evidence considered low quality. Two of these found:

  • Compared to cryospray, tetrafluoroethane that freezes the tissue, 5% imiquimod was less effective (RR 0.60, 95% CI 0.46 to 0.78; 1 study, 74 participants).
  • Compared to 10% potassium hydroxide, 5% imiquimod was also less effective (RR 0.65, 95% CI 0.46 to 0.93; 2 studies, 67 participants).
  • Other comparisons finding one treatment more effective than another tended to be based on studies with a small number of participants and with wide confidence intervals reducing the reliability of the evidence.
  • It is possible that some treatments are more effective than placebo but the quality of the evidence is too poor to make any recommendation.

What does current guidance say on this issue?

The British Association of Dermatologists in 2015 suggest that many treatments are painful and it is often better not to treat as the spots will go away by themselves. They further add that it is almost always best not to treat children, especially if it will cause pain.

What are the implications?

Unless new evidence emerges for the benefit of one treatment over another, molluscum contagiosum should be left to heal naturally. One topical treatment (5% imiquimod) was no more effective than a placebo and had more severe adverse effects.

However, there was insufficient evidence to assess the effectiveness of other treatments currently recommended such as curettage (applying anaesthetic and scraping off the spots) or cryotherapy using liquid nitrogen.

If more studies are conducted, it would be useful to measure recurrence rates, the spread of the disease to other people, disease-related quality of life and scarring as these were not well reported in the existing evidence.

Citation and Funding

van der Wouden JC, van der Sande R, Kruithof EJ, et al. Interventions for cutaneous molluscum contagiosum. Cochrane Database Syst Rev. 2017;5:CD004767.

Bibliography

British Association of Dermatologists. Molluscum contagiosum. London: British Association of Dermatologists; 2015.

NHS Choices.  Molluscum contagiosum. London: Department of Health; 2017.

NICE CKS. Molluscum contagiosum. Scenario: Management of molluscum contagiosum. London: National Institute for Health and Care Excellence Clinical Knowledge Summaries; 2012.

Why was this study needed?

Molluscum contagiosum is a viral skin infection and transmission occurs by close personal contact or via contaminated surfaces. The exact prevalence is unknown as many people do not seek medical attention but in a 2005 UK general practice-based survey of patient records, the annual incidence of new cases was 261 per 100,000 patients and 80% of cases are in children under 15.

It is generally a harmless condition that gets better within a few months without specific treatment but rarely, it can spread around the body and take up to 18 months or more to clear completely.

Treatment is often sought for cosmetic and social reasons or to prevent spread, however, the scientific basis for treatment is unclear and practitioners may be unsure whether to recommend treatment or not. The current study aimed to evaluate treatment options to see what worked if anything.

What did this study do?

This study reviewed 22 randomised controlled trials involving 1,650 participants - mostly children - with molluscum contagiosum. The trials compared 20 topical treatments (applied to the skin) and two oral treatments with either an alternative treatment or placebo in people who were not immunocompromised. Follow-up ranged from three to 28 weeks after randomisation. Only five studies had follow-up longer than three months.

The main outcome was a short-term clinical cure (up to three months after treatment start), shown by complete clearance of lesions.

Quality of evidence overall was judged to be low as most studies had small sample sizes and many had a high drop-out rate. The control comparison group was often an alternative treatment rather than a placebo, which may have shown some treatment effect which makes the overall effectiveness difficult to judge.

What did it find?

For 5% imiquimod cream compared to placebo:

  • Moderate-quality evidence showed a lack of effect for clinical cure either in the short-term (relative risk [RR] 1.33, 95% confidence interval [CI] 0.92 to 1.95; 4 studies, 850 participants), medium-term (RR 0.88, 95% CI 0.67 to 1.14; 2 studies, 702 participants) or long-term (RR 0.97, 95% CI 0.79 to 1.17; 2 studies, 702 participants). High-quality evidence showed no difference in short-term improvements (RR 1.14, 95% CI 0.89 to 1.47, 4 studies, 850 participants). The clearance at six months was about 40% in either group.
  • Moderate-quality evidence showed application site reactions were more frequent (RR 1.41, 95% confidence interval [CI] 1.13 to 1.77), including severe application site reactions (RR 4.33, 95% CI 1.16 to 16.19).

There were 11 comparisons between different treatments with evidence considered low quality. Two of these found:

  • Compared to cryospray, tetrafluoroethane that freezes the tissue, 5% imiquimod was less effective (RR 0.60, 95% CI 0.46 to 0.78; 1 study, 74 participants).
  • Compared to 10% potassium hydroxide, 5% imiquimod was also less effective (RR 0.65, 95% CI 0.46 to 0.93; 2 studies, 67 participants).
  • Other comparisons finding one treatment more effective than another tended to be based on studies with a small number of participants and with wide confidence intervals reducing the reliability of the evidence.
  • It is possible that some treatments are more effective than placebo but the quality of the evidence is too poor to make any recommendation.

What does current guidance say on this issue?

The British Association of Dermatologists in 2015 suggest that many treatments are painful and it is often better not to treat as the spots will go away by themselves. They further add that it is almost always best not to treat children, especially if it will cause pain.

What are the implications?

Unless new evidence emerges for the benefit of one treatment over another, molluscum contagiosum should be left to heal naturally. One topical treatment (5% imiquimod) was no more effective than a placebo and had more severe adverse effects.

However, there was insufficient evidence to assess the effectiveness of other treatments currently recommended such as curettage (applying anaesthetic and scraping off the spots) or cryotherapy using liquid nitrogen.

If more studies are conducted, it would be useful to measure recurrence rates, the spread of the disease to other people, disease-related quality of life and scarring as these were not well reported in the existing evidence.

Citation and Funding

van der Wouden JC, van der Sande R, Kruithof EJ, et al. Interventions for cutaneous molluscum contagiosum. Cochrane Database Syst Rev. 2017;5:CD004767.

Bibliography

British Association of Dermatologists. Molluscum contagiosum. London: British Association of Dermatologists; 2015.

NHS Choices.  Molluscum contagiosum. London: Department of Health; 2017.

NICE CKS. Molluscum contagiosum. Scenario: Management of molluscum contagiosum. London: National Institute for Health and Care Excellence Clinical Knowledge Summaries; 2012.

Interventions for cutaneous molluscum contagiosum

Published on 18 May 2017

van der Wouden, J. C.,van der Sande, R.,Kruithof, E. J.,Sollie, A.,van Suijlekom-Smit, L. W.,Koning, S.

Cochrane Database Syst Rev Volume 5 , 2017

BACKGROUND: Molluscum contagiosum is a common skin infection that is caused by a pox virus and occurs mainly in children. The infection usually resolves within months in people without immune deficiency, but treatment may be preferred for social and cosmetic reasons or to avoid spreading the infection. A clear evidence base supporting the various treatments is lacking.This is an update of a Cochrane Review first published in 2006, and updated previously in 2009. OBJECTIVES: To assess the effects of specific treatments and management strategies, including waiting for natural resolution, for cutaneous, non-genital molluscum contagiosum in people without immune deficiency. SEARCH METHODS: We updated our searches of the following databases to July 2016: the Cochrane Skin Group Specialised Register, CENTRAL, MEDLINE, Embase, and LILACS. We searched six trial registers and checked the reference lists of included studies and review articles for further references to relevant randomised controlled trials. We contacted pharmaceutical companies and experts in the field to identify further relevant randomised controlled trials. SELECTION CRITERIA: Randomised controlled trials of any treatment of molluscum contagiosum in people without immune deficiency. We excluded trials on sexually transmitted molluscum contagiosum and in people with immune deficiency (including those with HIV infection). DATA COLLECTION AND ANALYSIS: Two review authors independently selected studies, assessed methodological quality, and extracted data from selected studies. We obtained missing data from study authors where possible. MAIN RESULTS: We found 11 new studies for this update, resulting in 22 included studies with a total of 1650 participants. The studies examined the effects of topical (20 studies) and systemic interventions (2 studies).Among the new included studies were the full trial reports of three large unpublished studies, brought to our attention by an expert in the field. They all provided moderate-quality evidence for a lack of effect of 5% imiquimod compared to vehicle (placebo) on short-term clinical cure (4 studies, 850 participants, 12 weeks after start of treatment, risk ratio (RR) 1.33, 95% confidence interval (CI) 0.92 to 1.93), medium-term clinical cure (2 studies, 702 participants, 18 weeks after start of treatment, RR 0.88, 95% CI 0.67 to 1.14), and long-term clinical cure (2 studies, 702 participants, 28 weeks after start of treatment, RR 0.97, 95% CI 0.79 to 1.17). We found similar but more certain results for short-term improvement (4 studies, 850 participants, 12 weeks after start of treatment, RR 1.14, 95% CI 0.89 to 1.47; high-quality evidence). For the outcome 'any adverse effect', we found high-quality evidence for little or no difference between topical 5% imiquimod and vehicle (3 studies, 827 participants, RR 0.97, 95% CI 0.88 to 1.07), but application site reactions were more frequent in the groups treated with imiquimod (moderate-quality evidence): any application site reaction (3 studies, 827 participants, RR 1.41, 95% CI 1.13 to 1.77, the number needed to treat for an additional harmful outcome (NNTH) was 11); severe application site reaction (3 studies, 827 participants, RR 4.33, 95% CI 1.16 to 16.19, NNTH over 40).For the following 11 comparisons, there was limited evidence to show which treatment was superior in achieving short-term clinical cure (low-quality evidence): 5% imiquimod less effective than cryospray (1 study, 74 participants, RR 0.60, 95% CI 0.46 to 0.78) and 10% potassium hydroxide (2 studies, 67 participants, RR 0.65, 95% CI 0.46 to 0.93); 10% Australian lemon myrtle oil more effective than olive oil (1 study, 31 participants, RR 17.88, 95% CI 1.13 to 282.72); 10% benzoyl peroxide cream more effective than 0.05% tretinoin (1 study, 30 participants, RR 2.20, 95% CI 1.01 to 4.79); 5% sodium nitrite co-applied with 5% salicylic acid more effective than 5% salicylic acid alone (1 study, 30 participants, RR 3.50, 95% CI 1.23 to 9.92); and iodine plus tea tree oil more effective than tea tree oil (1 study, 37 participants, RR 0.20, 95% CI 0.07 to 0.57) or iodine alone (1 study, 37 participants, RR 0.07, 95% CI 0.01 to 0.50). Although there is some uncertainty, 10% potassium hydroxide appears to be more effective than saline (1 study, 20 participants, RR 3.50, 95% CI 0.95 to 12.90); homeopathic calcarea carbonica appears to be more effective than placebo (1 study, 20 participants, RR 5.57, 95% CI 0.93 to 33.54); 2.5% appears to be less effective than 5% solution of potassium hydroxide (1 study, 25 participants, RR 0.35, 95% CI 0.12 to 1.01); and 10% povidone iodine solution plus 50% salicylic acid plaster appears to be more effective than salicylic acid plaster alone (1 study, 30 participants, RR 1.43, 95% CI 0.95 to 2.16).We found no statistically significant differences for other comparisons (most of which addressed two different topical treatments). We found no randomised controlled trial evidence for expressing lesions or topical hydrogen peroxide.Study limitations included no blinding, many dropouts, and no intention-to-treat analysis. Except for the severe application site reactions of imiquimod, none of the evaluated treatments described above were associated with serious adverse effects (low-quality evidence). Among the most common adverse events were pain during application, erythema, and itching. Included studies of the following comparisons did not report adverse effects: calcarea carbonica versus placebo, 10% povidone iodine plus 50% salicylic acid plaster versus salicylic acid plaster, and 10% benzoyl peroxide versus 0.05% tretinoin.We were unable to judge the risk of bias in most studies due to insufficient information, especially regarding concealment of allocation and possible selective reporting. We considered five studies to be at low risk of bias. AUTHORS' CONCLUSIONS: No single intervention has been shown to be convincingly effective in the treatment of molluscum contagiosum. We found moderate-quality evidence that topical 5% imiquimod was no more effective than vehicle in terms of clinical cure, but led to more application site reactions, and high-quality evidence that there was no difference between the treatments in terms of short-term improvement. However, high-quality evidence showed a similar number of general side effects in both groups. As the evidence found did not favour any one treatment, the natural resolution of molluscum contagiosum remains a strong method for dealing with the condition.

Expert commentary

Molluscum contagiosum is a common viral skin infection seen mostly in children. It causes clusters of small pimple-like spots, which get better by themselves in a few weeks. Worried parents often consult doctors and nurses to prescribe something to get rid of the spots.

This very large survey has reviewed recent scientific studies looking to see if there is any decent evidence supporting the use of any specific treatment. In short, there isn’t any good evidence.

In fact, some treatments, such as imiquimod cream, can cause soreness. The best advice is to leave molluscum alone to get better spontaneously.

Dr Richard Logan, Consultant Dermatologist, Princess of Wales Hospital