Warts are contagious but completely harmless, growing on the skin or mucous membranes such as the nostrils. A wart affects only the top layers of the skin (it has not roots, seeds, or branches) and so, in theory, it should be possible to remove it with no more than a little discomfort.

Caused by the human papilloma virus H.P.V. (of which there are 70 different types, although not all are associated with warts), there are at least 30 different types of warts which can affect various parts of the body, principally the hands, face, neck, and genitals. Common warts, which are particularly prevalent in young children, are firm, sharply defined and usually round, although some are irregular in shape. They range in hue from flesh-coloured to brown, and can be anything up to ¼ inch (6mm) in diameter, often with a rough surface. Common warts usually appear on parts of the body that are prone to injury, such as the hands, face, knees, and scalp.

Also common on the wrists, backs of hands and the face are flat warts, so names because they are flat-topped. They can be itchy but you should try to resist the temptation to scratch, since it is scratching that causes the virus to spread, leading to the appearance of more warts.

As you get older, you may discover small, finger-like growths, sometimes dark in colour, growing on your face, neck, or arms. These are completely harmless and are known as digitate or filoform warts.

The bane of the public swimming pool communal changing rooms, plantar warts, commonly called veruccas, are simply flat warts which occur on the soles of the feet. They don’t look like the flat warts you might find elsewhere on the body because they have become flattened by the pressure exerted on them. In fact, this prevents them from growing outwards and forces them inwards, which can make them more painful. They appear hard and horny to the touch. Veruccas sometimes occur singly, sometimes in clusters.

In spite of being classified as a sexually transmitted disease, genital warts are part of the same harmless family of growths. They are transmitted by sexual contact and can appear anything up to 18 months after infection, emerging as extensive, pink, cauliflower-like areas on the genitals. Since there have been links with genital warts and cases of cervical cancer, women affected by genital warts should be particularly careful about keeping up-to-date with smear tests.