Usually they are skin-coloured, but may be brown, grey, yellow or black. They start as smooth, firm lesions, but enlarge and often develop a rough texture. Their size is variable and may be single or in groups. Almost any area may be affected, but the most common sites are the feet, hands and fingers. Less commonly they are found on the elbows and knees.
Anogenital warts occur typically near the genitalia and anus.
The penile shaft is a common site for males. Universal factors Warts are contagious. The warm water has a pH of less than 5, the skin is softened and the horny skin layer is swollen by the water - all factors which encourage penetration. Natural history When the virus first penetrates the basal layer, hyperkeratinisation starts as a small, smooth area. It gradually enlarges and the skin often becomes rough.