Introduction

Warts are non-cancerous (benign) skin growths that develop on different parts of the body and can take on various forms. They are caused by viruses. Warts are contagious and very common: Most people will have one at some point in their lives. Although they can affect people at any age, warts are most common among children and teenagers.

Most warts are harmless and will go away on their own within a few weeks or months. But they can be bothersome and unattractive, and some people feel embarrassed. There are a number of different treatments that can make warts go away more quickly – but they don't always work.

Viral warts are not the same as “senile warts” (seborrheic keratosis), which usually first appear in older age and aren't contagious. They are also quite harmless, but permanent. This information is about viral warts only.

Symptoms

Most warts don't cause any bothersome symptoms. Some may cause itching, tightness or the feeling of pressure. Warts might be painful too, particularly those on the soles of your feet. Some warts have small black dots caused by clotted blood that has leaked from capillaries (very fine blood vessels in the skin).

Warts may appear alone or in groups, which are capable of covering larger areas of skin. The main types of warts include:

• Common warts are skin growths that range from the size of a pinhead to the size of a pea. They harden, making them scaly and rough to the touch. Common warts are often found on the back of the hands, the fingers, the skin around the nails, and on your feet.
• Plantar warts mostly occur on the ankles and soles of the feet. Those on the bottom of the feet and toes are sometimes referred to as verrucas. They can become quite large. Because the soles of your feet have to support your body weight, plantar warts do not grow outward like other kinds of warts. They are pushed inward when you stand or walk. This can cause pain or tenderness due to the pressure. It also makes it difficult to treat this kind of wart.
• Mosaic warts are white and about the size of a pinhead. They are usually found on the balls of the feet or under the toes, but may also spread and cover larger areas on the entire sole of the foot. Unlike plantar warts, they do not hurt when you walk because they are flatter.
• Filiform warts have a thread-like, spiky appearance, and sometimes look like tiny brushes. Because they often appear on the face, they are usually considered to be particularly bothersome.
• Flat warts are small, slightly raised warts that are often just a few millimeters wide. Sometimes they are light brown in color. They are most commonly found on the face, particularly on the forehead and cheeks. Hands and lower arms are often affected too.
• Genital warts are small hard nodules with rough surfaces. They are sexually transmitted and affect only the genital region. The treatment for genital warts is different from treatment for the other kinds of warts mentioned above, so genital warts are not included in this overview.

Some types of skin cancer may look like warts, but they are very rare.

Causes

Warts are caused by human papillomaviruses (HPV), of which there are more than 100 different types. These viruses can enter the skin through small cuts and cause extra cell growth. The outer layer of skin turns thicker and harder, forming a raised wart.

Wart viruses are mainly spread by direct skin contact, but they may also be spread by touching objects like towels or razors. They are more likely to infect moist and soft or injured skin.

Risk factors

Some people are at greater risk of developing warts. They include

• people who work with raw meat, for example at a butcher’s shop or slaughterhouse,
• children and teenagers who often use communal showers, for instance after sports or at the swimming pool,
• people with family members who have warts,
• children who share a classroom with a lot of children who have warts,
• People who have a weakened immune system: especially adults and children who have had an organ transplant or who have a serious disease like cancer or AIDS, and
• people with atopic conditions like eczema.

The viruses multiply in the skin. If someone has a weakened immune system, their body isn't always able to successfully fight them off. Other people have a greater risk of getting warts because they have more frequent contact with the viruses.

Prevalence

Warts are very common, especially among children and teenagers. Various studies have shown that up to 33% of children and teenagers have warts. They are estimated to be much less common in other age groups, affecting only about 3 to 5% of adults.

Outlook

Warts are almost always harmless for people with a healthy immune system. The body often builds up an immune response to the wart viruses over time, and the warts then disappear without treatment. The amount of time this takes varies greatly, depending on the type of virus and wart, as well as on the person’s general state of health.

Studies involving school-age children and teenagers showed that about 50% of them no longer had any warts after one year. After two years, about 70% of them no longer had any warts. There is hardly any research on the natural course of warts in adults.

It can be much more difficult for people who have a weakened immune system to get rid of warts.

Prevention

If you have warts, there are a few precautions you can take to avoid spreading them. These precautions may also help to prevent the warts from spreading to other areas of your own skin.

You can do the following things to avoid infecting others:

• Cover the warts with a waterproof plaster when you go swimming.
• Do not share towels, shoes, gloves or socks with others.
• Do not go barefoot at swimming pools, or in communal showers or changing rooms.
• Do not touch the warts.

In addition, the following things are recommended in order to stop warts from spreading to other areas of your own skin:

• Do not scratch the warts, otherwise the viruses might spread.
• Keep your feet dry.
• Change your socks every day.

The effectiveness of these recommendations hasn't been tested in studies, so it isn’t clear whether they work, or how well they work. Because the viruses that cause warts are highly contagious, it’s hard to completely prevent them from spreading. Also, it’s not easy to tell how someone got them since it can take months for a wart to develop after the skin becomes infected.

Because warts are almost always harmless and very common anyway, there is usually no need to avoid activities such as swimming and sports at school.

Treatment

Warts don’t normally have to be treated. They generally go away on their own after a few weeks or months. But sometimes it can take years. Warts can be bothersome and unattractive, though, so a lot of people want to get rid of them as fast as possible, and try to treat them.

Two main treatments are used for warts:

• Salicylic acid solution: This is put on the hardened skin of the wart several times a day over the course of a few weeks to gradually dissolve it. Most salicylic acid solutions are available over the counter at the pharmacy. Some of these products also contain lactic acid. The package insert contains a detailed description of how to use the product and what you need to be careful of. Salicylic acid may cause skin irritation, but it is usually well tolerated.
• Cryotherapy: Cryotherapy involves freezing the wart by applying liquid nitrogen. This is usually done by a dermatologist. The nitrogen is extremely cold, and destroys cells in the skin’s outer layer. The treatment is repeated several times with a break of at least one week between each session. Liquid nitrogen is very cold so it may cause brief stabbing pain, and the skin may turn red or swell afterwards. Blisters sometimes develop too.

Both of these treatments are generally effective, but don't always get every last wart. Plus, sometimes viruses might remain in the skin after treatment and then lead to the growth of new warts later.

There are a number of other treatment options for warts, but many of them haven’t been well studied.

It may be a good idea to have a doctor examine you before starting treatment if you have certain health risks, such as nerve damage in your feet (due to diabetes, for instance). Women who are pregnant or breastfeeding are also advised not to have treatment, just in case it might be harmful.

Sources

• Bruggink SC, Eekhof JA, Egberts PF, van Blijswijk SC, Assendelft WJ, Gussekloo J. Natural course of cutaneous warts among primary schoolchildren: a prospective cohort study. Ann Fam Med 2013; 11(5): 437-441. [PMC free article: PMC3767712] [PubMed: 24019275]
• Kwok CS, Gibbs S, Bennett C, Holland R, Abbott R. Topical treatments for cutaneous warts. Cochrane Database Syst Rev 2012; (9): CD001781. [PubMed: 22972052]
• Loo SK, Tang WY. Warts (non-genital). BMJ Clin Evid 2014.
• Sterling JC, Gibbs S, Haque Hussain SS, Mohd Mustapa MF, Handfield-Jones SE. British Association of Dermatologists' guidelines for the management of cutaneous warts 2014. Br J Dermatol 2014; 171(4): 696-712. [PubMed: 25273231]

• IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

  Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. We do not offer individual consultations.

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