The common wart is known as verruca vulgaris. They are caused by a viral infection of the skin. This occurs as a result of direct contact with the virus. They do not spread through the blood stream. They occur more commonly in children than adults. When they occur on the bottom of the foot, they are called plantar warts. This name is derived from the location of the foot on which they are found; the bottom of the foot is called the plantar aspect of the foot. A common misconception is that plantar warts have seeds or roots that grow through the skin and can attach to the bone. The wart may appear to have a root or seeds, but these are in fact small clusters of the wart just beneath the top layer of the skin. The wart cannot live in any tissue except the skin. Moist, sweaty feet can predispose to infection by the wart virus. They can be picked up in showers and around swimming pools. They are not highly contagious, but being exposed in just the right situation will lead to the development of the wart. Avoiding contact in the general environment is nearly impossible. If a member of the family has the infection, care should be taken to keep shower and tile floor clean. Children who have plantar warts should not share their shoes with other people. Young girls often share shoes with their friends and this should be discouraged.

Source: Kirk A. Koepsel, D.P.M.