Q: Our teen-age daughter had a plantar wart on the sole of her foot for a long time. It didn't seem to bother her. Now she's getting another one on the ball of her foot. It hurts when she walks. Should it be treated? How?
A: Warts on the bottom of the foot need be treated only if they are painful. It sounds like your daughter's has reached that point. The wart is pressed inward during walking, leading to pain. In addition, walking can stimulate further growth of the wart.
There are a number of treatments for warts. One treatment, salicylic acid plaster, is available over-the-counter. Cut a piece of plaster exactly the size of the wart (because the plaster can be very irritating to normal skin) and tape it firmly to the skin with adhesive tape. Leave the plaster in place for three to five days. Sweat mixes with the acid in the plaster and the solution penetrates the skin, destroying the wart. When you remove the plaster, the dead white tissue should be taken off (a pumice stone works well), and another piece of the plaster should be taped into place. It may take two to three applications to get rid of the wart completely, and it will sometimes return.
Another treatment option is the use of cantharadin, a solution available by prescription. Cantharadin is an extract of frozen blister beetle (honestly, we don't make this stuff up!). With a toothpick, apply the solution to the wart. Allow it to dry and then cover it with a non-porous, plastic tape followed by a piece of adhesive tape. One to two days later, remove the tape. There should be a small blister over the wart which will fall off in approximately one week. If any wart remains, it can be scraped with a pumice stone and the cantharadin reapplied. Three or four applications may be necessary.
Dr. Wilson is director of pediatric primary care of the Johns
Hopkins Children's Center; Dr. Joffe is director of adolescent medicine.