A plantar wart (also known as “Verruca plantaris”) is a wart caused by the human papillomavirus occurring on the sole or toes of the foot. (HPV infections in other locations are not plantar; see human papillomavirus.)
Plantar warts are usually self-limiting, but treatment is generally recommended to lessen symptoms (which may include pain), decrease duration, and reduce transmission.
Infection and development
It is estimated that 7–10% of the US population is infected. Infection typically occurs from moist walking surfaces such as showers or swimming pools. The virus can survive many months without a host, making it highly contagious.
Plantar warts are benign epithelial tumors caused by infection by human papilloma virus types 1, 2, 4, or 63. These types are classified as clinical (visible symptoms). The virus attacks the skin through direct contact, entering through possibly tiny cuts and abrasions in the stratum corneum (outermost
layer of skin). After infection, warts may not become visible for several weeks or months. Because of pressure on the sole of the foot or finger, the wart is pushed inward and a layer of hard skin may form over the wart. A plantar wart can be painful if left untreated.
Warts may spread through autoinoculation, by infecting nearby skin or by infecting walking surfaces. They may fuse or develop into clusters called mosaic warts.
A plantar wart is a small lesion that appears on the sole of the foot and typically resembles a cauliflower, with tiny black petechiae (tiny hemorrhages under the skin) in the center. Pinpoint bleeding may occur when these are scratched, and they may be painful when standing or walking.
Plantar warts are often similar to calluses or corns, but can be differentiated by close observation of skin striations. Feet are covered in skin striae, which are akin to fingerprints on the feet. Skin striae go around plantar warts; if the lesion is not a plantar wart, the cells’ DNA is not altered and the striations continue across the top layer of the skin.
Plantar warts tend to be painful on application of pressure from either side of the lesion rather than direct pressure, unlike calluses (which tend to be painful on direct pressure instead).
Prevention and treatment
Because plantar warts are spread by contact with moist walking surfaces, they can be prevented by not walking barefoot in public areas such as showers or communal changing rooms, not sharing shoes and socks, and avoiding direct contact with warts on other parts of the body or on other people. Humans build immunity with age, so infection is less common among adults than children.
Once a person is infected, there is no evidence that any treatment eliminates HPV infection or decreases infectivity, and warts may recur after treatment because of activation of latent virus present in healthy skin adjacent to the lesion. There is currently no vaccine for these types of the virus. However, treatments are sometimes effective at addressing symptoms and causing remission (inactivity) of the virus.
The treatment that will be effective in a particular case is highly variable. The most comprehensive medical review found that no treatment method was more than 73% effective and using a placebo had a 27% average success rate.