Warts and verrucas (verruca vulgaris): causes, treatment and spread

Warts are common skin growths caused by infection with the human papillomavirus, according to the British Association of Dermatologists. Those on the sole of the foot are called verrucae or verrucas. The NHS describes warts as firm and rough, usually skin-coloured but sometimes darker on black or brown skin, appearing on palms, knuckles, knees and fingers.

They are more common in children and teenagers than adults. The BAD stresses you do not get warts because you are dirty, and they are nothing to be embarrassed about.

The NHS shows several appearances. Common warts are firm and rough. Verrucas on the feet have tiny black dots under the hard skin and are more likely to be painful. Plane warts are round, flat and can be yellow, and you can have many. Mosaic warts are clusters spread over an area of skin and are common on feet and hands.

A wart that bleeds, changes in how it looks or is unusually painful needs a clinician to look at it, so that other causes can be excluded.

The virus passes by close skin-to-skin contact, or through shared use of contaminated objects or surfaces, such as the area around a swimming pool. The BAD says infection is more likely if skin is wet or damaged and that not everyone in contact with the virus will develop warts. The NHS says it can take months for a wart or verruca to appear after contact.

Practical measures from the NHS include washing hands after touching a wart, changing socks daily if you have a verruca, covering warts and verrucas with a plaster when swimming, and taking care not to cut a wart when shaving. Avoid sharing towels, flannels, socks or shoes, avoid biting nails or sucking fingers with warts, avoid walking barefoot in public places if you have a verruca, and do not scratch or pick.

The BAD says most warts disappear without treatment over time, that none of the many treatments is completely effective, and that waiting for them to go on their own is often the best thing to do. The NHS says you can treat a wart if it bothers you, keeps coming back or is painful.

For home treatment, the BAD recommends topical products containing up to 50% salicylic acid. Its steps are to soften the wart by soaking in hot soapy water, protect surrounding skin with Vaseline, pare the wart with an emery board or pumice stone, apply the product with a cotton bud, cover with a plaster overnight and remove it in the morning. Apply for 3 nights initially and then nightly if it causes no problems, stopping for a few days if it becomes too sore. The NHS adds that pharmacy creams, plasters and sprays can take up to 3 months to complete, may irritate the skin and do not always work, and should not be used on the face.

Cryotherapy, freezing the wart with liquid nitrogen, is the usual next step. A GP may be able to freeze a wart so that it falls off a few weeks later, sometimes needing a few sessions, but the NHS says to check whether it is funded in your area, and the BAD says it is not routinely available on the NHS.

If treatment has not worked or a wart is on the face, the NHS says a GP may refer you to a dermatologist. A large or very painful verruca may lead to a podiatrist, who can offer stronger medicines than those available from a pharmacist, cryotherapy with liquid nitrogen, or surgery to remove the verruca with a scalpel or laser. You can also pay to see a podiatrist privately.

People with a weakened immune system, including those taking medicines that suppress it, may have warts that are more of a problem and harder to treat, according to the BAD.

The NHS recommends seeing a GP if you are worried about a growth on your skin, a wart or verruca keeps coming back, it is very large or painful, it bleeds or changes in how it looks, or it is on your face or genitals. Genital warts are treated at sexual health clinics. A new, changing or non-healing skin lump should never be assumed to be a wart.

Most people never need more than pharmacy advice. NHS cryotherapy availability varies by area, and podiatry, dermatology or private foot clinics may offer it if you want faster treatment.

Ask what the treatment involves, how many sessions are likely, whether it will hurt, and what the realistic chance of clearance is. Be sceptical of any provider that promises a guaranteed cure, because the dermatology evidence is that none of the treatments is completely effective.