Foot Warts

Overview

Plantar foot wart is the benign (noncancerous) growth, or foot wart, that occurs on the sole (plantar surface), heel, or ball of the foot. Pressure from standing and walking often causes them to grow into deep layers of the skin.

The human papilloma virus (HPV) causes several different types of foot warts, which are the most common type of skin infection. In some cases, the HPV virus dies within 1 or 2 years, and foot warts simply disappear. Podiatrist, or foot doctor, may recommend having plantar foot warts removed because they often are irritating and painful.

Incidence and Prevalence

Anyone can contract the virus that causes plantar foot warts. According to the American Podiatric Medical Association (APMA), plantar warts occur most often in children and young adults between the ages of 12 and 16. Incidence is higher in people who share common bathing areas (e.g., dormitory students, gym members).

Cause and Risk Factors

Plantar warts can occur when HPV invades the body through tiny cuts or breaks in the skin on the bottom of the feet. The virus often is encountered on contaminated surfaces, such as the tile floors of public locker rooms, showers, and swimming pools. Normally, antibodies in the blood destroy HPV, but in some cases, it takes refuge in the skin and causes plantar warts.

Some people are more prone to the virus that causes plantar warts than other people. Risk factors include repeated HPV exposure (e.g., walking barefoot in public locker rooms and common bathing areas) and having a weakened immune system.

Signs and Symptoms

Plantar warts usually are rough and spongy, and most are gray or brown with dark pinpoints (tiny capillaries that supply blood to the wart). Scraping a wart may cause it to bleed.

A plantar wart is similar in structure to an iceberg-the part on the surface of the skin is a small part of the entire anomaly. Often, the portion of the wart under the skin is at least twice as big as the part you can see.

Plantar warts may cause pain on the bottom of the foot. Patients often feel a "lump" on the bottom of the foot when standing, similar to having a stone in the shoe. In many cases, pressure from standing and walking prevents plantar warts from rising above the skin surface.

If left untreated, plantar warts can grow up to 1 inch in circumference and may spread into clusters (called mosaic warts). In severe cases, they cause a change in gait or posture that results in leg or back pain.

Wart Removal

Most plantar warts are diagnosed based on their appearance. In some cases, the podiatrist, or foot doctor, scrapes a sample of skin cells from the wart and sends the sample to a pathologist for microscopic evaluation.

Treatment

Over-the-counter medications contain chemicals that destroy skin cells (e.g., acid) and may damage healthy tissue surrounding the foot wart. Self-treatment for plantar warts using an over-the-counter preparation is not recommended.

In some cases, a podiatrist, or foot doctor, applies mild acid (e.g., salicylic acid, cantharidin, dichloroacetic acid) topically to treat plantar warts. This treatment, which often requires multiple applications over the course of several weeks, disintegrates viral cells and allows healthy skin cells to replace them.

Laser treatments (e.g., CO2 laser cautery) can be used to treat plantar warts. Laser treatment is performed in a podiatrist's office or an outpatient surgery facility using local anesthesia. Lasers produce little scarring and are effective in most cases.

Cryotherapy involves freezing warts with a very cold solution (e.g., sodium nitride) that destroys the virus and causes the wart to turn black and fall off within a few days. This treatment is ineffective in some cases when the solution does not penetrate far enough to completely destroy the virus.

Surgical wart removal (called debridement) usually is not recommended to treat plantar warts because it can cause painful scarring. Generally, this procedure is used for wart removal of several small warts in a limited area. Debridement is performed using anesthesia and can be used with acid to destroy the virus and prevent the warts from regrowing.

Prevention

According to the American Podiatric Medical Association (APMA), the following may help to prevent plantar warts:

• Avoid walking barefoot whenever possible.
• Change shoes and socks daily.
• Keep feet clean and dry.
• Check children's feet periodically.
• Avoid direct contact with warts on other persons or on other parts of the body.
• Do not ignore growths on, or changes in, your skin.
• Visit a podiatrist, or foot doctor, as part of your annual health checkup.