Warts

What is a wart?

A wart is a small, rough growth on the skin caused by a common virus called the human papillomavirus (HPV). Warts are harmless and very common; most people will have one at some point in their life.

What are the symptoms of a wart?

A wart typically:

• looks like a raised growth with a rough, textured surface, though some types are smooth and flat
• is skin-coloured, though it may appear darker on black or brown skin
• is sometimes flecked with small dark specks, which are tiny, clotted blood vessels
• ranges in size from a pinhead to a few centimetres
• can appears singly or in groups.

Warts don't usually cause other symptoms, but they can catch on clothing or be knocked, which is painful. Warts on the sole of the foot (verrucas) are flattened by the pressure of walking and can be particularly uncomfortable. Warts around or under the nails can be difficult to treat.

What are the causes of warts and who is at risk?

Warts are caused by the human papillomavirus (HPV). There are over 100 strains of HPV, but only a small number of these cause the warts seen on skin.

The virus can pass from person to person through close skin contact, or indirectly through contaminated surfaces such as swimming pool surrounds, especially where the skin is wet or damaged. However not everyone who comes into contact with the virus goes on to develop one, and it isn't fully understood why some people are more prone to warts than others.

You may be more likely to develop warts, or find them harder to treat, if you:

• are a child or teenager (warts are most common between the ages of 12 and 16, though they can appear at any age)
• have a weakened immune system, for example due to a medical condition or medicines that suppress the immune system
• have eczema
• work handling raw meat, fish or poultry.

Are there different types of wart?

Yes. Warts are usually grouped by their appearance and where they occur:

• Common warts: These are raised, with a rough surface, and appear most often on the hands, though they can develop anywhere on the body.
• Plantar warts (verrucas): These occur on the soles of the feet. The pressure of walking flattens them, and they can be painful. A cluster of several plantar warts growing close together is known as a mosaic wart.
• Flat warts: These are smaller, smoother and flatter than other types, and tend to grow in large numbers, most often on the face, hands or legs.
• Filiform warts: These are thread- or finger-like growths that most often appear on the face, particularly around the eyelids and lips.
• Periungual warts: These grow around or under the nails in a cauliflower-like cluster, and can be difficult to treat because of their location.
• Genital warts: These develop on or around the genitals and are sexually transmitted. They're managed differently from other warts, so if you think you have genital warts, it's best to be seen at a sexual health clinic.
• Butcher's warts: These develop on the hands of people who regularly handle raw meat, and tend to look similar to common warts.

How is a wart diagnosed?

A wart is usually diagnosed just by looking at it. Paring away the surface can sometimes reveal small dark dots underneath, which are tiny clotted blood vessels – a typical feature of warts.

A biopsy, where a small sample is removed and examined under a microscope, is occasionally used if there's any doubt about the diagnosis.

How is a wart treated?

Most warts disappear on their own without treatment as the immune system fights off the virus. Studies suggest around half of warts clear within 1 year, and about two-thirds within 2 years, so it's reasonable to leave a wart alone if it isn't causing problems.

If you decide to treat it, non-surgical options include:

• Salicylic acid: This is available from a pharmacy as a gel, liquid or plaster (strengths vary, typically 17 to 40%) – soak the wart in warm water, gently file away the dead skin with a pumice stone or emery board, then apply the treatment (usually daily) for several weeks
• Duct tape: Place it over the wart and replace it every few days – this is low-risk, though evidence for how well it works is mixed
• Cryotherapy: This is where a doctor or nurse freezes the wart with liquid nitrogen – this usually needs 3 to 4 sessions every 2 to 3 weeks and can cause blistering – in the UK, this is not always routinely available on the NHS
• Prescription topical treatments: Such as imiquimod, for warts that do not respond to the treatments above.

If you have diabetes, poor circulation, or a weakened immune system, check with a doctor before treating a wart yourself.

Surgical options are used less often, usually for warts that have not responded to other treatments, and can include:

• Curettage and electrodesiccation: The wart is scraped away and the base treated with an electric current – this is usually avoided on the soles of the feet
• Excision: The wart is cut out under local anaesthetic
• Laser treatment: Uses focused light to destroy the wart tissue.

Surgical treatments are more likely to leave a scar than topical treatments or leaving the wart to clear on its own.

When should I see a doctor?

See a GP, pharmacist or dermatologist if:

• the wart is painful, spreading, or bothering you
• it keeps coming back after treatment
• it bleeds, grows quickly, or changes in size, colour or shape

you're over 50 and develop a new wart-like growth you have a weakened immune system and develop persistent or widespread warts. Warts on or around the genitals should be checked at a sexual health clinic rather than treated as an ordinary skin wart.