What Are Plantar Warts?
Warts are caused by an infection of the skin by human papillomavirus (HPV), which is the most common viral infection of the skin. Plantar warts grow on the plantar surface or the sole of the foot. They can be found anywhere in this area but tend to produce symptoms in areas of pressure and friction. The virus that causes warts, the human papillomavirus, infects only the superficial layer of skin, producing a thickened callus-like growth that, if located in an areas subjected to pressure, can become quite tender.
Although warts characteristically resolve spontaneously, it is occasionally necessary to treat painful plantar warts. The incubation period (the period of time between infection and the production of the visible skin lesion) is unknown but estimates vary from months to years. Historical evidence is of little benefit in attempting to determine how one's wart was acquired. There are at least 120 different types of human papillomavirus (HPV), and certain types tend to infect specific anatomical areas, like the plantar surface of the foot. Other HPV types that infect oral or genital mucous membranes are implicated in the development of cervical cancer and other malignancies of the oral or anal lining tissues. HPV infections are ubiquitous infections, with least one-half of adults infected during their lifetime. The current prevalence of plantar warts in adults is unknown, but it is a fraction of the estimated 7%-10% of adults with all types of wart virus infections.
What Are Causes and Risk Factors of Plantar Warts?
The HPV types 57, 27, and 1a account for most plantar warts. The virus gains access to the skin through direct contact. It is presumed that inoculation of the skin occurs in places likely to be contaminated by others with plantar warts, like communal showers. Once infected by HPV, spontaneous resolution seems to depend on the development of immune lymphocytes that destroy the virus-infected cells. Vaccines are available to protect against certain types of genital viral infections, but there are no vaccines for the HPV types that cause plantar warts.
- Plantar warts are seen in all age groups, but they are most common among children 12-16 years of age and rare in the elderly.
- Risk factors for the development of plantar warts include
- use of public showers,
- skin trauma, and
- weakened immune system because of certain medications used or illness.
What Are Plantar Wart Symptoms and
- Foot pain localized to a thickened area on the sole
- Firm, warty (rough, bumpy, and spongy, some appear thick and scaly) lesions with tiny pinpoint dark spots in the body of the wart (not always apparent): These dark spots are minute, thrombosed (containing blood clots) capillaries in the deeper layers of the skin.
- Smooth surface with a gray-yellow or brown color
- Often located over areas of pressure or bony point such as the heel and ball of the foot
- Usually flat because of pressure
- Several warts may fuse to form "mosaic" warts.
Common Foot Pain Problems
Foot pain may be caused by a variety of problems. See photos of common foot problems, such as corns and calluses, plantar warts, gout, bunions, athlete's foot, hammertoe, ingrown toenails, and flatfoot.
What Specialists Treat Plantar Warts?
Usually a primary-care doctor can adequately treat plantar warts. If treatment under a family physician's care fails to work satisfactorily, a referral to a dermatologist (a skin specialist) may be necessary.
When Should Someone Seek Medical Care for Plantar Warts?
Call a doctor if simple home therapy fails to resolve the problem.
Corns and calluses, which can resemble warts, usually develop very gradually over several years. It is wise to consult a physician when one is unable to distinguish a plantar wart from a corn, callus, nevus (mole), or another type of skin lesion.
Most such growths are harmless, but some may pose a significant health risk. It is also possible for a variety of more serious lesions to appear on the foot, including malignant lesions such as carcinomas and melanomas. Although rare, these conditions can sometimes be misidentified as a wart.
- Seek medical attention for these conditions when
- you or your child have warts and want them removed;
- severe pain, redness, swelling, bleeding, or large lesions develop;
- removal by a physician by freezing or burning is desired;
- warts don't disappear completely after treatment; or
- other warts appear after treatment.
Plantar warts are rarely an emergency; however, the complications of aggressive therapy can be bleeding, severe pain, inability to walk, redness, swelling, streaking, and boil or abscess formation, which can all indicate an emergency.
How Do Doctors Diagnose Plantar Warts?
The diagnosis is typically made by observing the wart. If in doubt, the physician may send a tissue sample of the wart to a pathologist for examination.
The doctor may consider other problems that may cause a similar appearance, such as corns, calluses, or black heel (ruptured capillaries).
Are There Home Remedies for Plantar Warts?
Since warts generally go away on their own within months or years and leave no scar, treatment ought to be conservative, with destructive approaches being reserved after all else fails.
- For temporary relief of pain, place a doughnut-shaped piece of moleskin around the wart. This can be purchased at a drugstore.
- Since the source of discomfort in most symptomatic plantar warts is the thickened layer of horny skin between the nerve-bearing tissues and the ground, simple nontraumatic removal of this material is a good alternative. This can be accomplished with a pumice stone or some other type of abrasive material after the sole of the foot has been soaked in water for 20 minutes to soften the wart. Since the thickened surface keratin is identical to the keratin found in any callus, its painless. Bloodless removal by careful paring with a corn or callus trimmer is a reasonable alternative. Recently, a battery powered abrasive wheeled device (Amope) has become available, which ought to be useful in removing excess keratin. People with diabetes or peripheral artery disease or individuals who have numbness due to peripheral neuropathy should avoid paring.
- Salicylic acid
- Another technique to remove the excess keratin is an over-the-counter salicylic acid preparation, available at the pharmacy in liquid, gel, pad, or ointment form. Some familiar brand names are Dr. Scholl's Wart Remover, Compound W, Freezone, and Wart-Off. Be sure to follow package directions because over-application of these products can irritate the skin. Periodically sand and retreat the wart. It can take several months to get rid of a large one using these treatments. Warts can spread, so monitor your feet closely and treat warts when they are small.
- Soak the affected area in warm water for five minutes before applying the salicylic acid. This will enhance the effects of the medication.
- Remove any loose tissue with a brush, washcloth, or emery board and dry thoroughly. It is also important to file away as much of the overlying callus tissue as possible so that the medication can penetrate the wart properly.
- In general, one should see improvement in one to two weeks. If such treatment does not yield results after several weeks, see a doctor for more aggressive methods of wart removal.
- The prolonged use of this medication is not recommended, especially in infants, people with diabetes, and others with impaired circulation.
- Salicylic acid should only be used on warts or calluses and not on other types of skin conditions or lesions.
- A commercial preparation containing about 17% salicylic acid and 17% lactic acid in a fast-drying solution (for example, DuoFilm or Dermatech Wart Treatment) can be applied daily after showering. The preparation is allowed to dry and the wart covered with waterproof tape, which is removed after the next shower or bath. An individual can pare the wart once a week with a sharp blade (or a family member can do it). It may take many months to clear the wart with this method.
- The application of "duct tape" is a safe and possibly effective treatment approach worth trying. Any color duct tape is applied to the wart, which is kept covered 24 hours a day, six out of seven days a week, for six weeks.
What Are Treatments for Plantar Warts?
Doctors may choose from several different techniques for removing plantar warts.
- Acid: One of the most common methods is to burn warts off with a mild acid applied topically to the wart. Many applications may be required over the course of several weeks to achieve this, but the technique is highly successful. Salicylic acid and dichloroacetic (or trichloroacetic) acid are useful.
- Other acid methods may be used.
- Upton's paste: Upton's paste consists of six parts salicylic acid and one part trichloroacetic acid in glycerin, mixed to a stiff paste (ordered by prescription).
- A piece of thick adhesive tape (such as Leukoplast), with a hole cut in the middle for the wart, is applied to the sole to isolate the wart. Upton's paste is applied to the wart, and the whole area is covered with a second piece of tape. This is kept dry and intact for one week. The wart is then pared (shaved down) and the paste reapplied until clearance occurs.
- Salicylic acid in white soft paraffin: A mixture of 40%-60% salicylic acid in white soft paraffin is applied daily after showering and covered with waterproof tape. Pare the wart once a week with a sharp blade.
- Efudex (5-fluorouracil), used off-label, is another topical ointment that has been used to treat warts.
- Laser treatment: New technology has enabled doctors to use lasers to destroy the wart. The procedure, performed in the physician's office, is expensive and is likely to result in some scarring. Its efficacy in comparison to other destructive approaches in unproven.
- Cryotherapy: Freezing warts with liquid nitrogen is frequently successful. This causes the wart to turn black and eventually fall off within a few days. If used properly, there should be no scarring.
- Curettage and desiccation: After injecting a local anesthetic, the physician uses an electrical or ultrasonic device to destroy the wart, the remainder of which is removed with a curette. This technique is likely to cause a scar. (Note: The excision of warts is not recommended since the surgery may leave a painful scar, and it is common for warts to return in the scar tissue.)
- Oral medication: No oral medication has proven effective in the treatment of warts.
- Immunotherapy: For plantar warts that are resistant to treatment, one may be referred to a dermatologist for immunotherapy, which creates an immune response against foreign substances. Occasionally, the injection of Candida skin test antigen into warts is effective if the patient is skin test positive to this material.
- Rarely, certain chemotherapeutic agents (like bleomycin [Blenoxane]) are injected directly into the wart.
- There are many other treatments available for the treatment of plantar warts. No single therapy is so effective that it has eliminated the use of all others. Ultimately, all treatments rely on the patient's immune system to recognize the wart virus proteins and to produce an immune response that will rid the body of this annoying problem.
Follow-up for Plantar Warts
Follow the physician's directions. Overuse of prescribed medicines can lead to damaging results.
Is It Possible to Prevent Plantar Warts?
- Avoid walking barefoot, except on sandy beaches. Use shower thongs or sandals, particularly in public shower rooms.
- Change shoes and socks daily.
- Keep feet clean and dry.
- Check children's feet periodically.
- Avoid direct contact with warts from other people or from other parts of the body. Don't touch warts on other people. To keep from spreading warts, don't scratch them. Warts spread readily to small cuts and scratches.
- Do not ignore growths on, or changes in, the skin.
- Avoid sharing socks, shoes, and showering facilities.
- Protect the skin from injury, and wash hands frequently. Warts should be covered with waterproof tape in wet environments such as showers and swimming pools to avoid infecting oneself or others.
What Is the Prognosis of Plantar Warts?
Regardless of the home treatment or medical treatment used, a cure is not guaranteed. Warts may reappear at any time. Most therapies require several treatments and strict adherence to them. Work with a doctor or dermatologist to determine which therapy is best.
- In up to 60% of cases, plantar warts exhibit "spontaneous remission." This disappearance of the wart is because of the action of the body's immune system.
- Untreated, plantar warts may grow up to 1 inch across and spread into clusters. Since certain HPV types are oncogenic (able to produce invasive malignant cancers), it is possible that plantar warts can rarely become invasive malignancies. Any wart-like lesion on the sole of the foot that does not resolve after appropriate therapy and continues to enlarge should be biopsied and examined by a pathologist.
- A painful scar on the sole of the foot can pose an even more severe problem, which is why excisional surgery is not a desirable treatment option.
- Many of these warts resolve within one to two years. While they last, though, the warts are ugly, irritating, and often painful. For these reasons, many podiatrists (foot specialists) recommend having plantar warts treated.
- Warts can grow back. This indicates a virus is still in the body and growing. However, this is not cause for undue alarm. The type of HPV that causes plantar warts is relatively harmless and causes few problems. Warts can spread to other parts of the body, particularly if scratching a wart causes it to bleed. Blood from a wart contains the virus and can cause a new wart to grow in an area that it touches.
- Infection, pain, and scarring may result from overly aggressive home therapy penetrating beneath the skin surface. Pain can spread to other sites, and warts can be transmitted to others because of ineffective treatment.
Reviewed on 9/11/2017
Bruggink, Sjoerd C., et al. "HPV type in plantar warts influences natural course and treatment response: Secondary analysis of a randomised controlled trial." Journal of Clinical Virology 57 (2013): 227-232.
Cardoso, J.C., and E. Calonje. "Cutaneous manifestations of human papillomaviruses: A review." Acta Dermatoven APA 20.3 (2011): 145-154.
De Planell-Mas, Elena, et al. "Human Papillomaviruses Genotyping in Plantar Warts." Journal of Medical Virology. DOI 10.1002/jmv.24713.
Kollipara, Ramya, et al. "Advancements in Pharmacotherapy for Noncancerous Manifestations of HPV." J Clin Med 4.5 May 2015: 832-846.
Lipke, M. "An Armamentarium of Wart Treatments." Clinical Medicine & Research 4.4 Dec. 1, 2006: 273-293.
Naymor, M. "Cutaneous Human Papillomavirus Infections." The Electronic Textbook of Dermatology. <http://www.telemedicine.org/warts/cutmanhpv.htm#plantar%20etiology>.
"Plantar Warts." Warts Information Center. <http://www.warts.org/types-of-warts.html>.