A plantar wart (also verruca plantaris or commonly known as verruca) is a wart caused by the human papillomavirus (HPV) occurring on the sole or toes of the foot. (HPV infections in other locations are not plantar; see human papillomavirus.) Plantar warts are harmless and self-limiting, but should be treated to lessen symptoms (which may become painful), decrease duration, and reduce transmission.
Infection and development
It is estimated that 7-10% of the US population is infected. Infection typically occurs on moist walking surfaces such as showers, swimming pools, or shoes. 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, 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. Plantar warts may also spread to other parts of the body. 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 (abnormal, thrombosed capillaries resembling specks) 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 helomata 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 helomata (which tend to be painful on direct pressure instead).
Prevention and treatment
Because plantar warts are spread by contact with moist walking surfaces, avoid walking barefoot in public areas such as showers or communal changing rooms. You should avoid sharing shoes and socks, and avoid direct contact with warts on other parts of the body or on other people. Humans build immunity with age, so that 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.
Some treatments that have been found to be effective include:
are considered specialists in the treatment of plantar warts, though most warts are treated by primary care physicians
As warts are contagious, precautions should be taken to avoid spreading.
Pharmaceutical treatments Keratolytic chemicals
: The treatment of warts by keratolysis
involves the peeling away of dead surface skin cells with trichloroacetic acid
or salicylic acid
: Intralesional injection of antigens (mumps
, candida or trichophytin antigens USP) is a new wart treatment which may trigger a host immune response to the wart virus, resulting in wart resolution. Distant, non-injected warts may also disappear. Chemotherapy
: Topical application of dilute glutaraldehyde
(a virucidal chemical, used for cold sterilization of surgical instruments) is an older effective wart treatment. More modern chemotherapy agents, like 5-fluoro-uracil, are also effective topically or injected intralesionally. Retinoids
, systemically (eg. isotretinoin
) or topically (tretinoin
cream) may be effective.
- Liquid nitrogen : Cryosurgery with liquid nitrogen. A common treatment that works by producing a blister under the wart. It is painful but usually nonscarring.
- Electrodesiccation and surgical excision produce scarring. If the wart recurs, the patient has a permanent scar along with the wart.
- Lasers may be effective, especially the 585nm pulsed dye laser which the most effective treatment of all, and does not leave scars, but is generally a last resort treatment as it is expensive and painful, and multiple laser treatments are required (generally 4-6 treatments repeated once a month until the wart disappears).
- Cauterization may be effective as a prolonged treatment. As a short-term treatment, cauterization of the base with anaesthetic can be effective but risks scars or keloids. Subsequent surgical removal is unnecessary, and risks keloids and recurrence in the operative scar.
- Duct tape occlusion therapy: The wart is kept covered with duct tape for six days, then soaked and debrided with a pumice stone. The process is repeated for 6 to 8 weeks. The efficacy of this method has recently been called into question.
- Watchful waiting may be appropriate since many warts will eventually resolve due to the patient's own immune system. In many cases, the body will attack and kill the wart and verrucæ will turn black and effectively fall off, although it can be two years or longer before this takes place. Additional disadvantages with this method are significantly increased likelihood of passing on the virus and the possibility that in some individuals the virus may spread more extensively over the skin surface, further increasing discomfort and making treatment more difficult and requiring it to be more extensive.
- Hyperthermia through the immersion of the wart in hot water (113ºF or 45ºC) for 30 minutes to 3 hours, 2–3 times per week, up to 16 treatments.
- X-ray is an old method that is seldom recommended due to the long term adverse side effects of irradiation.
Relative effectiveness of treatments
A 2006 study assessed the effects of different local treatments for cutaneous, non-genital warts in healthy people. The study reviewed 60 randomized clinical trials dating up to March 2005. The main findings were:
- overall there is a lack of evidence (many trials were excluded because of poor methodology and reporting).
- the average cure rate using a placebo was 27% after an average period of 15 weeks.
- the best treatments are those containing salicylic acid. They are clearly better than placebo.
- there is surprisingly little evidence for the absolute efficacy of cryotherapy.
- two trials comparing salicylic acid and cryotherapy showed no significant difference in efficacy.
- one trial comparing salicylic acid and duct tape occlusion therapy showed no significant difference in efficacy.
- evidence for the efficacy of the remaining treatments was limited.
- Mayo Clinic
- Advice from UK Society of Chiropodists and Podiatrists
- Warts, The Merck Manual
- Plantar Wart photo library at Dermnet