Warts are caused by a virus called the human papilloma virus (HPV). They are very common, school children and those with a weak immune system being particularly at risk. Research suggests between 10 and 30 per cent of children and teenagers have warts at any given time, and most people will have a wart at some point during their lifetime.
There are more than 100 strains of HPV and several different types of wart, for example, warts on the sole of the foot, which are referred to medically as verruca plantaris.
Warts are highly contagious, that is, they are easily passed on to other people. In addition to the virus being passed on by direct skin-to-skin contact, it may be passed from person to person indirectly, for example, by sharing towels and shoes, or at swimming pools. Wet, soft, cut and exposed skin is more prone to infection by HPV.
Cutting and scratching warts may disperse the wart virus, which is why shaving can pose a high risk of infection. Scratching a wart may transfer the virus to the fingers, and subsequently to different parts of the body. People who scratch a wart and then bite their nails or suck their fingers may develop facial warts. Despite warts being contagious, it may take weeks or months for an infection to manifest as a wart.
TYPES
The appearance of warts varies dramatically in both size and appearance, and partly depends on the strain of the HPV. Some warts are small, while others may grow to over 10mm in diameter. For most people, the main symptom is cosmetic, particularly with facial warts.
Filiform warts, known as verruca filiformis, are often seen on the face and nostrils. They have long, hair-like projections, which make them a particular cosmetic concern to patients and parents. Common warts are also referred to as verruca vulgaris. These tend to be round and rough in appearance, often described by doctors as cauliflower-like.
This type of wart is most commonly seen on the hands and knees. The skin on the sole of the foot affected by verruca plantaris looks rough and white, sometimes with a black blood vessel at its core. Some people wrongly assume that the vessel, which looks like a black dot at the centre of the wart, is the virus itself.
Verruca plantaris may be painful to walk on. Plane warts (verruca plana) tend to be no bigger than 4mm in diameter and often affect the face and hands of young children. Leg shaving may also pre-dispose women to plane warts. This type of wart tends to appear in clusters, which may contain more than 100 lesions.
Mosaic warts also grow in clusters and tend to occur on the palms of the hands and soles of the feet. Warts may grow either around or even underneath finger or toenails. These so-called periungual warts may be painful and distort the affected nail.
TREATMENT
In the main, your doctor will find warts straightforward to identify, although there may be occasions when a referral to a dermatologist is required to confirm the diagnosis.
The body will mount an immune response to HPV and clear up to 80 per cent of warts within 24 months. The chance of spontaneous clearance without treatment is much higher in children than adults. Some research even suggests that in young children, treatments are no more effective than leaving the body to fight the warts on its own.
If the warts cause pain or affect functioning such as vision or walking ability, your doctor may elect to treat them. There are various treatment options available, none of which is completely effective, and a combination of treatments may be required.
Cryotherapy usually destroys HPV by applying a cold burn with liquid nitrogen or over-the-counter alternatives. The treatment is painful and may cause blistering, hence is not recommended for facial warts or for use on young children.
There is medical evidence that products containing salicylic acid can successfully treat around 70 per cent of warts within 12 weeks of treatment, with little in the way of side-effects. A number of different preparations of salicylic acid are available, including gels and plasters.
Whichever preparation is used, it is important to file away the dead skin overlying the wart, soak the skin prior to application and protect the healthy surrounding skin. Salicylic acid should not be used on the face.
Covering the wart with duct tape for six days at a time has been suggested as an alternative treatment to salicylic acid. The tape may need to be applied repeatedly over a two-month period. The medical evidence, however, supporting the use of duct tape is poor and the adverse effects are commonplace.
The key messages with typical warts are that they are common and contagious. It is often best, unless there are particular concerns, to leave the body to fight them off on its own rather than pursue treatments. Nevertheless, if concerned, always consult your doctor.
Dr Raj Thakkar BSc(Hons) MBBS MRCGP MRCP(UK) is a full-time GP in Buckinghamshire.
