What causes warts?
Plantar warts are contagious. They are caused by a virus and may multiply and spread to adjacent areas of skin. Plantar warts can occur anywhere on the bottom of the foot. They start as solitary warts and then spread over a larger area. The virus is found most commonly on the moist floors of public facilities like gyms, locker rooms and public pools. They can be spread from person to person within a household, across shower bottoms and bathroom floors.
Plantar warts can occur at any age but are most commonly found on the hands and feet of children between the ages of 12 and 19. The immune system gets better at recognizing and defending against the wart virus as we get older.
If you look closely at a wart you will notice that the skin lines either go around it or stop at its edges. There may be small black dots within it. A wart will hurt more if it is pinched from side to side than if direct pressure is applied to it.
Salicylic acid applied to the surface of the wart can work quite well. This treatment's advantages are that there is almost no risk of forming a painful scar on the bottom of the foot and it requires no healing time. The disadvantage is that it takes several weeks. In our office, we generally use salicylic acid patches at a concentration of 40 percent. The peel-and-stick patches are cut to fit and left in place continuously. Showers may be taken with the patches in place. The dead portion of each wart is painlessly shaved off once a week in the office.
Surgical removal can be done by numbing the area of the wart and using either a sharp instrument or a curette or both. Sometimes this is followed by the application of a chemical to lower the rate of recurrence which is about 15 percent per wart. This means that a second procedure is usually necessary if there are seven or more warts.
Freezing treatments for plantar warts can cause them to spread because the skin is too thick to freeze completely. The incomplete freezing causes inflammation which probably causes the spread.
Bleomycin, an anticancer drug, is used for very resistant warts. The two most resistant spots are on the toes and the back of the heel. A couple of days following injection, the warts turn red and blisters form. A week later they are shaved off in the office.
The virus is killed by Lysol or bleach applied on the surfaces of the shower floor or tub and across the surface of the bathroom floor. Once warts appear, the best prevention is early treatment before they spread. Because the cause is viral, new warts can appear up to several months following treatment.
Posted by Mark A. Kuzel, DPM, FACFAS on September 8, 2010