Warts are common and usually harmless. They are caused by the human papillomavirus (HPV). Treatment is often not required or appropriate as the majority resolve spontaneously. Studies into the efficacy of the numerous possible treatment options continue to give conflicting results.
Incidence is thought to be higher in children of school age than in preschool children and to peak in teenage years.
Warts are caused by HPV.There are well over one hundred types of HPV. Types 1, 2, 3, 4, 10, 27 and 57 are most often implicated in the aetiology of cutaneous warts. Infection of keratinocytes causes hyperkeratinisation and epidermal thickening.
HPV infection is acquired from direct contact with an affected individual or from the environment (eg, from contaminated floors or surfaces). It appears the virus can survive outside the body for a significant length of time, probably months or even years.
Trauma and wetness are contributory in contracting warts. The virus is more likely to spread around other parts of the body if the wart is damaged by trauma or scratching.
Warts are classified according to their appearance or site. The British Association of Dermatologists (BAD) guidelines recognise the following four subtypes:
Common wart (verruca vulgaris)
By Lucien Mahin, via Wikimedia Commons
These appear as papules and nodules with a keratotic and papillomatous surface. They occur anywhere but are most common on the hands in young people and children.
Plane wart, or flat wart (verruca plana)
These are slightly elevated, flat-topped warts which may occur singly or in a group of many lesions.
Plantar wart, or verruca (verruca plantaris)
These are warts on the sole of the foot and are discussed in the separate Verrucae article.
Genital wart (condyloma acuminatum)
These are discussed in the separate Human Papillomavirus and Genital Warts article
These are warts around the nails. They are more common in people who bite their nails.
Filiform wart (verruca filiformis)
These are small finger-like warts consisting of hyperkeratotic projections. They arise most often on the face or neck.
These are groups or clusters of plantar, or occasionally palmar, warts.
This is usually obvious clinically but, if necessary, paring down will produce pinpoint bleeding of the capillaries in the roots of the wart.
- Actinic keratosis
- Cutaneous horn
- Lichen planus
- Lichen nitidus
- Molluscum contagiosum
- Prurigo nodularis
- Seborrhoeic keratosis
- Squamous cell carcinoma
- Corns and calluses
- Malignant melanoma
- Basal cell carcinoma
Warts eventually resolve without therapy, so if they are asymptomatic and the individual is not immunocompromised, they do not necessarily need treatment. Treatment is time-consuming and may have side-effects so should only be recommended if the wart is symptomatic or the person requests it.
Topical salicylic acid has the best evidence base and is normally first-line treatment. There is no evidence for one preparation being more effective than another. The wart should be pared down prior to application. Daily treatment for at least 12 weeks is required.
Cryotherapy with liquid nitrogen every two weeks until the wart has gone (up to four months) may be effective. Clinicians vary in how long they freeze the wart for; usually liquid nitrogen is applied until a ring of frozen tissue is visible around the wart, typically 5-30 seconds. There is no evidence that there is any difference in effectiveness between a spray and a cotton bud. Over-the-counter preparations do not reach such low temperatures and are probably not as effective. Reported cure rates vary hugely. Cryotherapy may be painful, may cause blistering and should be avoided in young children.
Applying salicylic acid (once the blistering from the cryotherapy has resolved) in between cryotherapy sessions may be beneficial. Again, the evidence is equivocal.
Other treatments used in secondary care
A whole host of other treatments is used. These have been subject to trials of varying quality. BAD guidelines include the following potential options in their recommendations:
- Physical removal by surgery, curettage, laser, or photodynamic treatment.
- Antimitotic agents such as:
- Podophyllotoxin - topical
- Retinoids - topical or oral
- Bleomycin - intralesional
- Virucidal agents such as:
- Immunomodulatory agent, including:
- Imiquimod 5% - topical
- Interferon - intralesional
- Dinitrochlorobenzene - topical
- Diphencyprone - topical
- 5- fluorouracil (5-FU) - topical
- Acupuncture (for plane warts)
Of these, the best evidence of efficacy is for bleomycin, 5-FU, laser and topical immunotherapy agents; however, all evidence is weaker than that for salicylic acid and cryotherapy.
Treatments used in the past but found by BAD to have insufficient evidence to recommend their use include:
- Occlusion with duct tape
- H2-receptor antagonists
- Herbal treatments
When to refer
Reasons to consider referral to secondary care include:
- Uncertain diagnosis.
- Persistent symptomatic warts unresponsive to primary care treatment.
- Multiple warts in immunocompromised individuals.
- Facial warts. Facial warts should not be treated in primary care.
- Extensive coverage (eg, mosaic warts).
In children, warts tend to resolve more quickly than in adults. Resolution has been shown to occur in half of children within a year and in two thirds within two years.This was either with or without active treatment. In adults, warts may take several years to resolve.
Complications are rare but include local infection or spread and malignant change. Such events are more common in immunocompromised people.
The risk of auto-inoculation can be reduced by avoiding biting the area (eg, nail biting), picking at the wart, trauma and maceration of the involved skin. Advise keeping nail files and pumice stones used for filing warts separate and not using for other areas of skin.
Further reading and references
; Management of cutaneous viral warts. BMJ. 2014 May 27348:g3339. doi: 10.1136/bmj.g3339.
; British Journal of Dermatology, July 2014
; NICE CKS, December 2014 (UK access only)
; DermNet NZ
; Topical treatments for cutaneous warts. Cochrane Database Syst Rev. 2012 Sep 129:CD001781. doi: 10.1002/14651858.CD001781.pub3.
; Natural course of cutaneous warts among primary schoolchildren: a prospective cohort study. Ann Fam Med. 2013 Sep-Oct11(5):437-41. doi: 10.1370/afm.1508.
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