Warts are very common, and often develop as small, rough lumps, which resemble solid blisters, or have a ‘cauliflower’ type appearance. Warts are caused by infection with the human papilloma virus (HPV), a family of over 100 viruses, some of which cause warts on the feet, hands or face. Other types of HPV only infect the tissue of the genital tract, which are referred to as ‘genital warts’. Warts can be spread by contact with skin infected by HPV, and also by contact with objects that have touched warts, such as towels. Genital warts are spread by sexual contact.
While everyone is at risk of developing warts, they most commonly affect children aged 12 to 16 years. It is estimated that one in five children have warts, and without medical treatment, about 65 per cent of wart infections spontaneously resolve. While there is no link between warts and the development of skin cancer, HPV are now recognised as major causes of cervical cancer.
The parts of the body most commonly affected by warts include the face, hands, knees and feet. While the characteristics of warts depend on the type, symptoms usually involve the development of a raised bump on the skin, which is roughly 1 to 10 millimetres in diameter. Warts can also be smooth or rough, and occur singly or in groups. Sometimes the lump that develops into a wart can be itchy or uncomfortable. HPV causes warts by attacking the skin through direct contact. The virus often enters the skin through small cuts or abrasions in the stratum corneum (outermost layer of skin). After the virus infects the skin cells, warts can develop quickly, or in several weeks to months.
Types of warts
Many different types of wart have been identified, which vary in size or shape, by the region of the body that they infect, and by the type of HPV that causes the infection. These include:
Common wart (Verruca vulgaris)
Common warts are raised, and have a roughened surface, which is often likened to a ‘cauliflower’ appearance. These types of warts are most common on the hands and knees, and occur most frequently in children. Common warts are a result of localised infection of the epidermis (the outer layer of the skin covering the body) with types 2 and 4 of the HPV, and usually resolve spontaneously.
Flat wart (Verruca plana)
Flat warts are flesh-coloured, small in size and have a smooth and flattened shape. They are very common on the face in large numbers, but are also seen on the neck, wrists, hands and knees. Flat warts are very common in children, and are caused by the HPV types 3 and 10.
Filiform or digitate wart (Verruca filiformis)
These types of warts are composed of single, or many thread or finger like projections, which are called papillae. Filiform or digitate warts are most common on the neck and face, especially near the eyelids and lips
Plantar wart (Verruca pedis)
Plantar warts develop on the soles of the feet as hard lumps, which can be very painful. These warts are caused by infection by HPV types 1, 2, 4, and 63, and often contain multiple black specks in their centre.
Mosaic warts occur as groups of tightly clustered plantar-type warts, which aggregate to form a mosaic like appearance. They are commonly found on the hands or soles of the feet and are usually caused by HPV type 2.
Genital wart (Condylomata acuminata)
Genital warts are characterised as small benign (harmless) lumps on or around the genitals and anus area. They appear as grey to off-white lumps that have a rough ‘cauliflower’ appearance. Genital warts are commonly caused by HPV types 6 and 11, and because they are sexually transmitted, the penis, vulva and anus are most commonly affected. HPV may also cause flat, abnormal growths on the cervix (the lower part of the uterus that extends into the vagina).