This kind of warts usually occurs on the soles (plantar area) of the feet. It is therefore also known as plantar warts. The plantar wart is often contracted by walking barefoot on dirty surfaces or littered ground where the virus is lurking. The causative virus thrives in warm, moist environments, making infection a common occurrence in communal bathing facilities. Most plantar warts do not have a lumpy surface like common warts because of the pressure of walking flattens them and also makes the surface hard. The appearances of plantar warts may look gray or brown with a centre that appears as one or more pinpoints of black. They also have a bad reputation for being very painful.
If the wart is left untreated, warts can grow to an inch or more in circumference and can spread into clusters of several warts. This is often known as mosaic warts. Like any other infectious lesion, plantar warts are spread by touching, scratching, or even by contact with skin shed from another wart. The wart may also bleed. This is another route for spreading.