2. Common warts (verrucae vulgaris) are normally painless horny projections of skin, usually on the hands, caused by various types of the human papilloma virus (HPV). Infection of keratinocytes by HPV causes hyperkeratinisation and epidermal thickening. Infection is acquired from direct contact with an affected individual or from the environment. HPV infection is very contagious, is easily spread from one site to another on an infected person and from one person to another. Verrucas (verrucae plantaris, plantar warts) are warts that occur on the sole of the foot, and are painful because of downward pressure on nerve endings in the skin above them.

Overall, warts are thought to affect around 10% of the population. Warts and verrucas are rare in young children, but prevalence rises with age to 15–20% of young people between 16 and 18, and falls significantly in adulthood. Verrucas occur most frequently in young people who regularly use swimming pools and communal washing/changing areas. Immunocompromised and immunosuppressed patients are particularly susceptible to warts and verrucas. There is also a high incidence of warts on the hands in people who handle fish or meat in their work. Untreated, half of warts and verrucas clear in 1 year and two-thirds in 2 years, but they are usually treated to get rid of them faster.