Plantar warts are, simply warts that grow on the bottom [ i.e. the plantar surface] of the feet. Like warts found elsewhere on the body they are caused by the human papillomavirus (HPV). Plantar warts tend to occur on the heels or the balls of the feet, which take the most pressure from standing and walking. You can pick up the HPV that causes the warts anywhere, but you're most likely to come into contact with it in warm, moist places such as shower floors, locker rooms and public swimming pools. You're most susceptible to HPV if you're repeatedly exposed to the virus, if your skin is cut or damaged, or if your immune system is weakened.
These warts can look like small, fleshy bumps; hard, flat growths with a rough surface and well-defined boundaries; or gray or brown lumps with tiny pinprick size black dots (clotted blood vessels that distinguish warts from bloodless corns and calluses). The growths interrupt the normal lines and ridges in the skin.
You don't really have to do anything about plantar warts. Most will disappear on their own sooner or later. But if yours are causing you discomfort, a number of treatments are available. You can buy over-the-counter treatments containing a 40 percent salicylic acid solution that you apply once or twice a day for a few weeks. Another option is the "duct tape treatment" - you cover the warts with duct tape for six days then soak them in water and rub them gently with an emery board or pumice stone. You may have to repeat the process over the course of a month or two before the warts disappear, but a study published in the October 2002 Archives of Pediatrics and Adolescent Medicine found that the duct tape method worked better than having a doctor freeze the warts off with liquid nitrogen, which can be painful and cause scarring.
My own preferred approach to removing warts is visualization -you simply spend a few minutes a day picturing the growths shrinking. If you need help coming up with images, you can listen to audiotapes made by practitioners skilled in guided imagery and clinical hypnosis. It may be most effective to do this when waking and falling asleep. Children are especially good at it - their vivid imaginations can conjure up all kinds of magical methods of wart removal. A man I know got rid of a troublesome wart by imagining a steam shovel scraping away at it morning and night. This mind-over-matter method can work remarkably well, and I urge you to try it before resorting to acids, duct tape, lasers, or surgery.
Andrew Weil, M.D.