Both are caused by infection of the skin by the human papilloma virus which initially gains entry to the body through a breach in the skins defences such as a small cut or abrasion. Our immune systems try to eliminate the infection and in most cases are successful and the warts disappear. Professor Cameron advisor to the ASA has provided us with the following details. There is much folk-lore about verrucas or plantar warts. Many have in the past, spent a great deal of time attempting to eradicate this problem.
Opinion nowadays tends to regard such attempts as a waste of time.
Injury of the skin is a prerequisite for the contraction of warts, hence, a predilection for the hands, knees and feet as these sites are more prone to minor injury during childhood activities particularly barefoot activities in changing rooms, gymnasia and especially swimming pools with the plantar skin being slightly soggy together with possibly damp duckboards or foot mats. Therefore the skin of the feet is more easily damaged by slight irregularities of the floor surface in order to implant the virus which could be present on the pool surround. This is possibly the reason why such warts occur less often in adolescents and adults, because by the time that adolescence is reached, most individuals have reached an adequate immunity. This is, therefore, sufficient to cover that period during which contraction of such warts is likely to occur. Many feel that because the virus is so widespread, it could be beneficial to spread it as much as possible and as early as possible in the lives of children.