Warts are small lumps that often grow on the skin of the hands and feet. These growths of the skin are very common and non-cancerous, they are caused by infection of a virus. Warts can differ in appearance. Most often warts will be round or oval shaped and have a hard, scaly surface with a small black dot (called a seed) in the centre of each spot. This black dot is due to a small clotted blood vessel. There are several different types of wart and they can develop as a single wart or in clusters. Different types of warts are more likely to affect different areas of the body. For example, a verruca is a type of wart that commonly develops on the sole of the foot. If the skin on the soles of your feet is damaged, you may be more vulnerable to verrucas. Warts are common in children and teenagers of school age, but can affect otherwise healthy adults. Warts are more common in people with weakened immune systems. Most people will have a wart at some point in their life.
Warts are caused by certain strains of the human papilloma virus (HPV). HPV is a family of viruses of which there are more than 100 different strains. The virus usually affects the skin and mucosa (the moist membranes) of the body causing an excess amount of keratin (a protein) to build up in the top layer of the skin (epidermis). This extra keratin in the epidermis produces the hard, rough texture of the wart and it is in these skin cells that the virus can be found.
HPV can be spread by close skin-to-skin contact. It can also be spread by autoinoculation which means the warts can spread to other parts of your own body. If a wart is picked, scratched or bitten, particles of the virus can spread to other areas of the skin. Even shaving your face or legs or biting your nails can spread the HPV. These viral particles can take as long as 12 months to develop into another wart. This ‘waiting time’ is called the incubation period. The virus can also be spread indirectly through contact with contaminated objects such as the areas surrounding swimming pools, exercise equipment, towels, floors of communal changing rooms and shoes.
To prevent getting and spreading warts you can take some simple precautions. Wear flip-flops around swimming pools or in communal changing rooms. Special waterproof plasters to put over warts or verrucas are available at many pharmacies and should be used if you or your child is going swimming. This will prevent the spread of infection to others. There is also a waterproof rubber verruca sock which many prefer to use instead of plasters.
For as long as the wart is present on your body it is thought to be contagious to other people and to other parts of your own body. Viral particles are more likely to spread to skin that is soft, wet, scratched or cut. If a wart breaks up or bleeds, this can also make it easier for the viral particles to spread. You may also be more vulnerable to persistent warts if you take certain medications such as azathioprine or cyclosporine or if your immune system is suppressed from such diseases as HIV (human immunodeficiency virus). Unfortunately in patients who have these types of diseases it can be almost impossible to get rid of the wart or warts.
Diagnosing a wart is usually relatively easy. The dermatologist will thoroughly examine the affected area of skin and in most cases will be able to diagnose a wart based on its characteristic appearance. Sometimes it can be useful to scrape off the very top layer of the wart to check for the small black dots which are common within warts. Also, a dermatologist can use a dermatoscope (a kind of magnifier) to help distinguish a wart from another lesion such as seborrheic keratosis. On the rare occasion a small section of the wart may be removed by shave biopsy and will then be sent to a laboratory for further analysis. This is sometimes done to rule out other types of skin growths or skin conditions.
A wart has the ability to hide from an otherwise normal immune system. Dermatologists at the London Dermatology Centre have a range of treatments to combat warts including a newer treatment which encourages the immune system to recognise the virally infected cells and eradicate them. The aim of any wart treatment is to remove the wart without leaving a scar. Most warts are harmless and can clear up without any treatment. However, it can take up to 2 years for the virus to leave your system and for the wart to disappear without treatment. Many people choose to treat their warts especially if the wart is painful, causing discomfort, is in an awkward place or embarrassing. There are many different treatment options available depending on a patient’s choice and preference. These treatments range from topical applications of salicylic acid to cryotherapy.
Salicylic acid is the most frequently used topical treatment for verrucas and warts. It is available in many forms such as creams, gels, paint and plaster. Salicylic acid is a very safe treatment but can have some minor side effects. It can also be used during pregnancy if limited to a small area for a short amount of time and if the formulation of salicylic acid does not contain podophyllin. It works by destroying the wart itself by removing the dead skin cells. However, it also acts against healthy skin so it is important to protect your skin before using the treatment. Readily available petroleum jelly or a small plaster can be used to cover the skin around the wart to protect the surrounding area from irritation. Prior to application of the salicylic acid you should soften the wart by soaking it in warm soapy water for 5 minutes. Then to encourage deeper penetration of the salicylic acid, you can file down the wart with an emery board or pumice stone. You may only have to do this once or twice a week. Do not share the emery board or pumice stone with others or use it on other areas of your body as you may end up spreading the HPV to other areas. Then apply the paint, gel or cream to the affected area and leave to dry. Finally cover it with a plaster or duct tape.
Cryotherapy involves freezing the wart to destroy the cells. This is also an effective and increasingly popular treatment. It is very safe if applied by a trained dermatologist and it can even be used to treat warts during pregnancy. A consultant dermatologist will apply liquid nitrogen to the wart for a few seconds and freeze the wart. Freezing the wart kills the affected skin cells causing a blister to form. This blister will be replaced naturally by a scab which will fall off in about one week. Each session of cryotherapy takes around 15 minutes and may be a little painful. Bigger warts may need several sessions of cryotherapy to clear them up. The freezing is usually repeated between 1 and 3 week intervals for around 3 months. Some pharmacies sell a type of ‘freezing’ aerosol spray treatment over the counter. The active ingredient in these sprays is not liquid nitrogen but another compound called dimethyl ether propane. Although it does feel cold when sprayed these sprays are not as effective as cryotherapy using liquid nitrogen.
Chemical treatments available on prescription include fomaldehyde, silver nitrate and glutaraldehyde. These work by attacking the skin cells of the wart and killing them. They also kill the healthy surrounding skin so it is important to protect the surrounding area before using these treatments. Silver nitrate can actually burn the surrounding area of skin so this should be used with particular caution. Glutaraldehyde can stain the skin brown. Other treatments include topical retinoids such as adapalene and tretinoin, fluorouracil cream and injections of bleomycin. Very few warts require electrosurgery, which is also called curettage and cautery. This procedure is only really used for large warts and is performed under a local anaesthetic. The wart is burned away and leaves a wound that takes around two weeks to heal. This treatment will leave a scar.
For more information regarding the treatment of warts please contact us on 020 7467 3720.
Content by Dr Sunil Chopra and Rebecca Perris
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