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Warts and all

Not many people know that Oliver Cromwell had Welsh ancestors, and had his grandfather not taken his grandmother's surname on marriage, he would have been known to posterity as Oliver Williams. Most people know he had a large wart on his face. Treating warts has always been of interest to Bandolier , it being one of those common conditions for which knowledge about effective treatments seems to be sparse. When a Cochrane review [1] comes up not only with some answers on available treatments, but much common sense about trial methodology, applause is in order.


The review had some ambitious aims to examine not only all available treatments, but also to examine trial evidence for clinically useful information, like differences between hands and feet, or untreated versus previously treated warts. In many of these reviewers were thwarted by lack of good evidence. As expected from a Cochrane review searching and basic methods were excellent. The criteria for a valid clinical trial of warts were addressed in a thoughtful way.


There were 49 randomised trials for inclusion. In general their methodological quality was poor, with 38 classified as low quality (allocation method, blinding and withdrawals not described) and only two as high quality (allocation method, blinding and withdrawals described, intention to treat analysis). Nine trials had intermediate quality.

Being definite about results from this data set could never be easy. The reviewers' conclusions are shown in Table 1. Topical salicylates were compared with placebo in six trials on non-refractory warts (Figure 1), and the NNT was 3.7 (2.7 to 5.5). Aggressive cryotherapy was compared with gentle cryotherapy in four trials (Figure 2) and the NNT was 4.7 (3.4 to 7.3). There was some evidence for topical dinitrocholorobenzene, but from tiny numbers.

Table 1: Main results of review of cutaneous wart treatments

Treatment Number of trials Reviewer conclusions
Topical salicylic and/or lactic acid 13 Six trials had placebo comparison. 75% of 191 patients cured with treatment and 48% of 185 with control. NNT 3.7 (2.7 to 5.6)
Cryotherapy 16 Four trials compared aggressive versus gentle cryotherapy. 52% of 304 patients cured with aggressive treatment and 31% of 288 with
gentle treatment. NNT 4.7 (3.4 to 7.3)
Intralesional bleomycin 5 Insufficient evidence of efficacy. No difference between bleomycin and placebo in two trials
Topical 5-fluorouracil 2 Some evidence of efficacy, but not discernably better than other, simpler, treatments
Intralesional interferons 6 Insufficient evidence of efficacy, including no difference between IFN alpha and placebo, and higher adverse events
Topical dinitrochlorobenzene 2 80% cure in 40 treated patients and 43% of 40 with placebo. NNT 2.7 (1.8 to 5.6). Some evidence of efficacy but tiny numbers
Photodynamic therapy 4 Pooling impossible because of different regimens, but some evidence of efficacy

Figure 1: Wart cures with topical salicylate and placebo

Figure 2: Wart cures with aggressive and gentle cryotherapy

For many other treatments, including lasers, imiquimod, surgery, aldehydes, podophyllin, podophyllotoxin, cantharidin and silver nitrate, there was little or no published evidence.


Does this help? It confirms that for commonly used treatments we have the best of what little evidence is available, and at least we know that we are not missing something. Most important is that we have only two (2) high quality trials about wart treatment, a common enough condition that is a source of much angst.

The review is brilliant in how it picks apart the relevant issues for performing wart trials in future. These include variables associated with participants (age, site and type of lesion, history of treatment) and treatments (including trial duration). No new trial should be undertaken without reference to this review. Some new trials (and new treatments?) are needed to better inform current and future treatment.


  1. S Gibbs et al. Local treatments for cutaneous warts (Cochrane Review). In: The Cochrane Library, Issue 4, 2001. Oxford: Update Software.
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