Victor, 11, presents to the minors area of your emergency department with a painful wart on his foot. It has been increasing in size over the last three months and is now so sore he can’t walk on it without a limp. His GP suggested trying duct tape, but Victor’s parents were skeptical about this. They’ve sought the advice of a local pharmacist, who sold them some salicylic acid cream.
He takes off his sock to reveal this:
What’s going on?
The darker area is the wart; the circumferential discoid scale lifted healthy skin due to either the salicylic acid or Upton’s paste damaging the normal skin around the wart.
Okay, so back to basics, what is a wart?
A wart is a non-cancerous squamoproliferative growth of the skin. Warts occurring on the feet are known as verrucae. They are caused by Human Papilloma Virus (HPV) and typically regress spontaneously in 6 months (25%) to two years (70%). Bruggink and colleagues found that one-half of primary schoolchildren with warts will be free of warts within one year, with younger age and non-Caucasian skin type increasing the likelihood of resolution.
Can we make them disappear any faster?
The short answer is … maybe. In addition to watchful waiting, the choices are essentially forms of either chemical trauma or physical trauma.
Popular chemical options include gently filing the wart’s apex with an emery board or similar and applying a substance to increase cell turnover. These include various strengths of salicylic acid paste or Upton’s paste APF (60% Salicylic acid with 10% trichloroacetic acid). Cryotherapy, curettage or electro-dissection are also used to remove warts.
How should we manage plantar warts?
A 2012 Cochrane review looked at topical treatments for warts. The 85 studies and more than 8000 patients did not identify any RCTs evaluating surgery (curettage, excision), formaldehyde, podophyllotoxin, cantharidin, diphencyprone, or squaric acid dibutyl ester. However, several RCTs looked at salicylic acid, duct tape and cryotherapy (with liquid nitrogen).
A number of trials compare salicylic acid to cryotherapy – one head to head trial of liquid nitrogen vs salicylic acid (the EVerT study), enrolled 240 patients, albeit mostly in their early 20s. The study showed no difference in wart resolution or side effect profile, although patient satisfaction was initially higher with salicylic acid. Notably, there was a drop in compliance and satisfaction by week three of a planned eight-week course for the salicylic acid arm. Authors observed a markedly lower cure rate (15%) than previous studies, which claimed that between one and two-thirds of warts resolved!
Of note, for cryotherapy in children, the added challenge is keeping the child still and not so fearful that the procedure fails. Daily dressings with salicylic acid and Vaseline provide an alternative set of challenges. A wide variety of regimens were used for each of the therapies studied.
Craw et al suggest that cryotherapy and salicylic acid may be used as first line, although in children salicylic acid is preferable. For the other therapies mentioned above (surgery, curettage et al.), they advised that they are for second line use only.
Victor agrees to sit still long enough – with the help of some nitrous oxide – for his wart to be removed and the base cauterised with silver nitrate (it demonstrated possible benefit in the 2012 Cochrane review). The wound is dressed, and advice for ongoing salicylic acid therapy and regular dressing changes is provided.
Just as he gets up to leave, Victor asks about the duct tape – his friend tried it, and it seemed to work.
Really? Duct tape??
Duct tape has been studied in three trials (193 patients); the mode of action is not well known, but at least one author has suggested a psychological component that is more effective in children than adults. It is popular as it is relatively harmless, although no better than a placebo.
The evidence surrounding management of warts is evolving and heterogeneous. Most will resolve unassisted, but the currently recommended first line therapies with either salicylic acid paste, cryotherapy or duct tape have all had some success in at least one trial, if the parents (and child) are keen to try an active intervention and can appropriately weigh up the potential harm or inconvenience vs the low likelihood of benefit.
(Many thanks to “Victor” and his family for consenting to these photographs being in the public domain.)
Bruggink SC1, Eekhof JA, Egberts PF, et al. Natural course of cutaneous warts among primary schoolchildren: a prospective cohort study. Ann Fam Med. 2013 Sep-Oct;11(5):437-41. doi: 10.1370/afm.1508.
Bruggink SC, Gussekloo J, Zaaijer K, et al. Warts: cryotherapy, salicylic acid or expectantly awaiting? A randomised controlled trial. J Invest Dermatol. 2008;128:8.
Bruggink SC, Gussekloo J, Egberts PF, et al.. Monochloroacetic acid application is an effective alternative to cryotherapy for common and plantar warts in primary care: a randomized controlled trial. J Invest Dermatol. 2015 May;135(5):1261-7. doi: 10.1038/jid.2015.1. Epub 2015 Feb 5.
Cockayne S1 Curran M, Denby G et al. EVerT: cryotherapy versus salicylic acid for the treatment of verrucae–a randomised controlled trial. Health Technol Assess. 2011 Sep;15(32):1-170. doi: 10.3310/hta15320.
Craw, L., Wingert A. & Lara-Corrales, I. Are salicylic formulations, liquid nitrogen or duct tape more effective than placebo for the treatment of warts in paediatric patients who present to ambulatory clinics? Paediatr Child Health Vol 19 No 3 March 2014
Gibbs S, Harvey I. Topical treatments for cutaneous warts. Cochrane Database Syst Rev2006;3:CD001781
Kwok CS, Gibbs S, Bennett C, et al. Topical treatments for cutaneous warts. Cochrane Database Syst Rev. 2012 Sep 12;(9):CD001781. doi: 10.1002/14651858.CD001781.pub3.