Patient education: Common warts, plantar warts, and flat warts (Beyond the Basics)

SKIN WARTS OVERVIEW — Skin warts are growths on the skin that are caused by a virus called human papillomavirus (HPV). HPV infection is common; there are different types, some of which can cause warts.

What are the different types of warts? — Examples of the types of warts HPV infection can cause include:

●Common warts (rough warts often found on the hands, knees, or other areas)

●Plantar warts (warts on the bottom of the feet)

●Flat warts (warts that appear as small, smooth bumps on the skin)

●Genital warts (warts in the genital area, also called "condyloma acuminatum")

The types of HPV that cause common warts, plantar warts, or flat warts are usually different from the types of HPV that cause genital warts. A vaccine is available to help protect against the types of HPV that cause genital warts (and increase a person's risk of certain types of cancer). More information on the HPV vaccine and genital warts is available separately. (See "Patient education: Human papillomavirus (HPV) vaccine (Beyond the Basics)" and "Patient education: Genital warts in women (Beyond the Basics)".)

Who gets warts? — Common, plantar, and flat warts are most common in children and young adults. People with certain jobs, such as handling meat, fish, and poultry, may also be more likely to develop common warts. People who have chronic skin conditions, such as eczema, and people with a weakened immune system (eg, from AIDS or after an organ transplant) may have more extensive warts or warts that are difficult to control.

How do you get warts? — People can become infected with the virus that causes warts (HPV) by touching another person's wart. HPV is more likely to infect skin that is injured or softened by water, but they can infect healthy skin as well. It can take up to six months or longer after exposure to the virus for a wart to appear.

What do warts look like? — Warts on the skin can have different appearances. A person may have a single wart or multiple warts:

●Common warts – Common warts usually appear as rough bumps on the skin (picture 1). The bumps are often round or oval in shape and less than one centimeter wide but occasionally join together or grow larger.

Common warts can occur in almost any body area. Frequent places for common warts are the hands and knees. When common warts are located around the fingernails, they are called periungual warts (picture 2).

●Plantar warts – Plantar warts are found on the soles of the feet. Plantar warts often begin as a small, round area of rough or thickened skin but may grow to involve larger areas (picture 3).

Close examination of a plantar wart will show that it interrupts the normal skin lines that are found on the soles of the feet. Small, clogged blood vessels, which look like black dots or tiny seeds, are also commonly seen in plantar warts.

●Flat warts – Flat warts usually appear as skin-colored, pink, or brown, small bumps on the skin (picture 4). Common places for flat warts are the face, top of the hands, top of the feet, arms, and legs.

SKIN WART DIAGNOSIS — Skin warts can usually be diagnosed based upon how they look. Skin biopsy or other testing is not usually necessary.

It is important to see your health care provider if a wart looks odd, grows rapidly, becomes painful, or does not get better with treatment. Skin cancer and other types of skin problems sometimes look similar to warts.

SKIN WART TREATMENT — Treatment of warts depends upon where the wart is located and how much it bothers you. Treatment is not necessary in all cases. For instance, two-thirds of skin warts in children will resolve on their own within two years, without treatment. However, during this time, the wart may enlarge or new warts may appear. In addition, a few small warts are usually easier to treat than multiple larger warts. For these reasons, most people choose to treat skin warts, particularly if they are painful, persistent, or bothersome in their appearance.

There are many ways to treat warts. Some treatments take several weeks or even months to work, and warts can come back after treatment. Plantar warts and periungual warts can be particularly difficult to eradicate with treatment.

People with diabetes or other diseases that can slow healing of wounds may have a higher risk for complications from some wart treatments. If you have one of these diseases and have developed skin warts, it's best to talk with your health care provider before trying any home treatments.

Also, if your child is at risk for ingesting treatments that you might try at home (eg, children with warts on the hands who thumb or finger suck), it is best to discuss treatment options with your health care provider before trying at-home treatments.

Treatment you can try at home

Salicylic acid — Salicylic acid is a type of acid that is applied directly to the wart. It comes in different forms, such as a liquid or patch.

If you decide to try salicylic acid treatment at home, you should follow the instructions on the package or your provider's instructions. This often involves first soaking the wart in warm water for five minutes, then drying the skin completely, and then applying the salicylic acid. These steps are repeated each day.

Thick or loose skin on the surface of the wart should be removed at least every few days. This skin often appears white after soaking. Removal of this skin helps the medication to penetrate better and can be performed by filing the surface of the skin with a pumice stone or nail file. It is common to have a small amount of bleeding during filing, but you should stop if the skin becomes painful.

If the wart does not go away within 12 weeks, you should stop treatment and see your health care provider.

If you have neuropathy (nerve damage that causes numbness), you should not use salicylic acid, as it could injure your skin without you realizing it.

Treatments performed by a health care provider

Liquid nitrogen — Liquid nitrogen, often called "cryotherapy," is a very cold liquid that destroys warts by freezing the skin. Liquid nitrogen must be applied by a health care provider, and multiple treatments are often needed to eliminate the wart.

Liquid nitrogen is often used to treat warts in older children and adults. The treatment can be difficult for younger children to tolerate because it can be painful.

After liquid nitrogen treatment, most people heal within four to seven days.

Liquid nitrogen can cause permanent loss of skin color in the areas treated. If you have concerns about how your skin will appear after treatment with liquid nitrogen, talk to your health care provider.

Cantharidin — Cantharidin is a liquid that is applied by a health care provider to treat skin warts. It may be particularly useful for young children because it causes no pain initially. However, some people develop pain, blisters, and swelling 2 to 24 hours after the treatment.

The skin usually heals within 5 to 10 days after treatment.

Shave excision — Shave excision is a procedure that involves removing a skin wart with a blade. A health care provider performs the procedure, usually after injecting local anesthesia to numb the skin.

Other treatments — Examples of other treatments that may be used for warts include fluorouracil cream (sample brand name: Efudex), imiquimod cream (sample brand name: Aldara), immunotherapy, injection of medications that have antiviral effects, and laser therapy. A health care provider prescribes or performs these treatments. Immunotherapy involves the application or injection of a substance to the wart to trigger a response from your body's immune (infection-fighting) system. These treatments are usually used for people with many warts or warts that do not respond to other treatments.

WHEN TO SEEK HELP — Consult a health care provider if:

●You are not sure if you skin growth is a wart.

●Your skin wart does not improve with home treatment or becomes painful. A health care provider should examine it to confirm that it is not a skin cancer or another skin condition.

●You would like to use home treatment, but are not sure which treatment is right for you.

●You have a wart that is bleeding or growing rapidly.

●You have been treated for warts and have developed signs of a skin infection, such as redness, pain, or pus-like drainage from the treated area. In some cases, redness and pain are normal reactions after wart treatment, so discuss possible side effects with your health care provider in advance.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Skin warts (The Basics)
Patient education: Seborrheic keratosis (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

This topic currently has no corresponding Beyond the Basics content

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Cutaneous warts (common, plantar, and flat warts)
Human papillomavirus infections: Epidemiology and disease associations

The following organizations also provide reliable health information.

●KidsHealth

     (https://www.kidshealth.org/en/parents/wart.html)

●Medline Plus

     (https://medlineplus.gov/ency/article/000885.htm, available in Spanish)

●American Academy of Dermatology

     (https://www.aad.org/public/diseases/a-z/warts-overview)

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