Common, harmless, and they usually disappear without treatment, warts and verrucae can easily be treated OTC if they are a nuisance or unsightly, as Alan Nathan explains

WHAT’S THE CAUSE?

Warts (common warts) and verrucae (plantar warts) are horny projections of skin caused by the human papillomavirus (HPV). HPV infection is very contagious – it is easily spread from one site to another on an infected person, and from one person to another. Warts most commonly occur on the hands, although they can appear on other areas of the body. Verrucae are essentially warts occurring on the soles of the feet, compressed under the weight of the body above them. Untreated, half of warts and verrucae clear within a year and two- thirds within two years, but they are usually treated to clear them faster.

HOW COMMON ARE THEY?

Warts and verrucae are rare in children under three years old. They occur in 5-10 per cent of children between four and six years old, rising to 15-20 per cent of 16- 18 year-olds, and falling significantly in adulthood. Males and females are equally affected. Immunocompromised and immunosuppressed patients are particularly susceptible. There is a high incidence of warts on the hands in people who handle fish or meat in their work. White people are twice as likely as black people or those of Asian descent to develop warts.

WHAT ARE THE SIGNS AND SYMPTOMS?

Common warts Usually found on the hands, fingers and elbows, and on the knees in children under 12, but they can occur anywhere on the body. They are rough, scaly, pink or skin-coloured papules with a papillomatous rough surface, usually of less than 1cm diameter but can be larger. They occur singly or in groups, and are normally painless.

Verrucae
• Occur on the plantar surface (sole) of the foot and are painful because of downward pressure on nerve endings in the skin.
• Most commonly occur where the ball of the foot is exposed to pressure
• Are often sore to touch and to stand or walk on.
•l Appear as areas of flat, thickened skin with a harder edge around a softer centre. On closer examination, or rubbing away the surface with a file or emery board, small black spots (telangiectasia, the ends of broken blood capillaries) can be seen.
• Occasionally, several verrucae appear together and coalesce to form a single large plaque known as a mosaic wart.

WHAT ELSE COULD IT BE?

Common warts
• Seborrhoeic warts. Similar in appearance to common warts but brown in colour, and occurring mainly on the back and chest. They are benign and occur increasingly with age.
• Skin tags. Benign, flesh-coloured or dark brown, flat or stalk-like papillomas, occurring mainly on the neck.
 • Basal and squamous cell carcinomas. Malignant growths with a wart-like appearance in the early stages, usually occurring in areas exposed to the sun.
Verrucae
• Plantar callus. Thick and painless patches of hard skin.
• Verrucous squamous cell carcinoma, a slow-growing cancer that rarely metastisises. It may be mistaken for a long-standing verruca.

RED FLAGS – WHEN TO REFER

• With warts, if basal or skin cell carcinoma is suspected.
• If verrucous squamous cell carcinoma is suspected.

OTC TREATMENTS

Treatment is the same for both verrucae and warts, and is gradual removal of the hyperkeratotic skin layers and the viral core by keratolytic agents.
Salicylic acid In the treatment of warts and verrucae, salicylic acid reduces viral numbers by mechanical removal of infected tissue. It also stimulates production of protective antibodies in response to the mildly irritant effect of the acid. Some products containing salicylic acid, including ointments and colloidon- based preparations, are the same as those marketed for corns and calluses. Daily treatment for up to three months may be necessary to completely remove warts or verrucae.
Lactic acid Lactic acid is included with salicylic acid in several verruca products. It is corrosive and is claimed to enhance the effects of salicylic acid. Care must be taken that preparations do not spread onto unaffected skin.
Trichloroacetic acid (TCA) A gel containing TCA is marketed as a medical device. TCA has a caustic and astringent action. The manufacturer claims that only four days’ treatment is required.
Formaldehyde and glutaraldehyde These have antiviral activity and a direct anhidrotic effect, drying the verruca and surrounding skin. Formaldehyde (0.75%) is available as an aqueous gel. Glutaraldehyde has similar properties to formaldehyde but appears to have no advantage over it and may be a more potent skin sensitiser. It also stains skin brown, although this fades once treatment is discontinued. It is available as a 10% paint.
Silver nitrate Silver nitrate is a caustic agent. It is used as a stick or pencil (95% toughened with 5% potassium nitrate) to destroy warts, verrucae and other skin growths. Unlike most other treatments, silver nitrate pencil is used for only a short period; Three to six daily applications are claimed to be sufficient.
Cryotherapy Aerosols containing dimethyl ether and propane (DMEP) for freezing warts and verrucae are available over the counter. They are used daily for up to 10 days. They are licensed as medical devices.

ADDITIONAL ADVICE

• Verrucae are often passed on at swimming pools. To minimise transmission of infection: an infected person should cover the verruca with a waterproof plaster when swimming, all swimmers should wear flip-flops in communal areas and showers and an infected person should not share shoes, socks or towels.
• Auto-infection of verrucae should be minimised by keeping feet dry and changing socks daily.
• Auto-infection of warts should be minimised by not scratching the skin or biting fingernails.
• Treatment of warts and verrucae must be continued until all traces have been removed, otherwise they may regrow.