Warts are one of several lesser afflictions of the foot, which nevertheless can be quite painful. They are caused by a virus, which typically invades the skin through small cuts and abrasions. They are frequently called plantar warts, because they appear most often on the plantar surface, or sole, of the foot. They can appear anywhere on the skin, however, and technically only those on the sole are properly called plantar warts.
Most warts are harmless and benign, even though painful.
They are often mistaken for corns, which are layers of dead skin that build up to protect an area which is being continuously irritated, whereas a wart is a viral infection. It is also possible that a variety of other more serious lesions, including carcinomas and melanomas, although they are not overly common, can be mistakenly identified as warts. The plantar wart is often contracted by walking barefooted on dirty surfaces or littered ground where the virus is lurking. If left untreated, warts can grow to an inch or more in circumference, and they can spread into clusters of several warts. Like any other infectious lesion, they are spread by touching and scratching, and even by contact with skin shed from another wart.