Common warts are small, grainy skin growths that occur most often on your fingers or hands. Rough to the touch, common warts also often feature a pattern of tiny black dots, which are small, clotted blood vessels.

Common warts are caused by a virus and are transmitted by touch. It can take a wart as long as two to six months to develop after your skin has been exposed to the virus. Common warts are usually harmless and eventually disappear on their own. But many people choose to remove them because they find them bothersome or embarrassing.

Common warts usually occur on your fingers or hands and may be:

• Small, fleshy, grainy bumps
• Flesh-colored, white, pink or tan
• Rough to the touch
• Sprinkled with black pinpoints, which are small, clotted blood vessels

When to see a doctor

See your doctor for common warts if:

• The growths are painful or change in appearance or color
• You've tried treating the warts, but they persist, spread or recur
• The growths are bothersome and interfere with activities
• You aren't sure whether the growths are warts
• You are an adult and numerous warts begin to appear, which may indicate the immune system is malfunctioning

Common warts are caused by the human papillomavirus (HPV). The virus is quite common and has more than 150 types, but only a few cause warts on your hands. Some strains of HPV are acquired through sexual contact. Most forms, however, are spread by casual skin contact or through shared objects, such as towels or washcloths. The virus usually spreads through breaks in your skin, such as a hangnail or a scrape. Biting your nails also can cause warts to spread on your fingertips and around your nails.

Each person's immune system responds to the HPV virus differently, so not everyone who comes in contact with HPV develops warts.

People at higher risk of developing common warts include:

• Children and young adults, because their bodies may not have built up immunity to the virus
• People with weakened immune systems, such as those with HIV/AIDS or people who've had organ transplants

To reduce your risk of common warts:

• Avoid direct contact with warts. This includes your own warts.
• Don't pick at warts. Picking may spread the virus.
• Don't use the same emery board, pumice stone or nail clipper on your warts as you use on your healthy skin and nails. Use a disposable emery board.
• Don't bite your fingernails. Warts occur more often in skin that has been broken. Nibbling the skin around your fingernails opens the door for the virus.
• Groom with care. And avoid brushing, clipping or shaving areas that have warts. If you must shave, use an electric razor.

In most cases, your doctor can diagnose a common wart with one or more of these techniques:

• Examining the wart
• Scraping off the top layer of the wart to check for signs of dark, pinpoint dots — clotted blood vessels — which are common with warts
• Removing a small section of the wart (shave biopsy) and sending it to a laboratory for analysis to rule out other types of skin growths

Most common warts go away without treatment, though it may take a year or two and new ones may develop nearby. Some people choose to have their warts treated by a doctor because home treatment isn't working and the warts are bothersome, spreading or a cosmetic concern.

The goals of treatment are to destroy the wart, stimulate an immune system response to fight the virus, or both. Treatment may take weeks or months. Even with treatment, warts tend to recur or spread. Doctors generally start with the least painful methods, especially when treating young children.

Your doctor may suggest one of the following approaches, based on the location of your warts, your symptoms and your preferences. These methods are sometimes used in combination with home treatments, such as salicylic acid.

• Stronger peeling medicine (salicylic acid). Prescription-strength wart medications with salicylic acid work by removing layers of a wart a little bit at a time. Studies show that salicylic acid is more effective when combined with freezing.

• Freezing (cryotherapy). Freezing therapy done at a doctor's office involves applying liquid nitrogen to your wart. Freezing works by causing a blister to form under and around your wart. Then, the dead tissue sloughs off within a week or so. This method may also stimulate your immune system to fight viral warts. You'll likely need repeat treatments.

  Side effects of cryotherapy include pain, blistering and discolored skin in the treated area. Because this technique can be painful, it is usually not used to treat the warts of young children.

• Other acids. If salicylic acid or freezing isn't working, your doctor may try trichloroacetic acid. With this method, the doctor first shaves the surface of the wart and then applies the acid with a wooden toothpick. It requires repeat treatments every week or so. Side effects are burning and stinging.
• Minor surgery. Your doctor can cut away the bothersome tissue. It may leave a scar in the treated area.
• Laser treatment. Pulsed-dye laser treatment burns (cauterizes) tiny blood vessels. The infected tissue eventually dies, and the wart falls off. The evidence for the effectiveness of this method is limited, and it can cause pain and scarring.

Home treatment is often effective in removing common warts. Unless you have an impaired immune system or diabetes, try these methods:

• Peeling medicine (salicylic acid). Nonprescription wart removal products such as salicylic acid are available as a patch, ointment, pad and liquid. For common warts, look for a 17 percent salicylic acid solution. These products (Compound W, Dr. Scholl's Clear Away Wart Remover, others) are usually used daily, often for a few weeks. For best results, soak your wart in warm water for a few minutes before applying the product. File away any dead skin with a disposable emery board or a pumice stone between treatments.

  If your skin becomes too irritated, decrease how often you use this method to treat your wart. If you're pregnant, talk with your doctor before using an acid solution.

• Freezing. Some liquid nitrogen products are available in nonprescription liquid or spray form (Compound W Freeze Off, Dr. Scholl's Freeze Away, others).

• Duct tape. Cover the wart with silver duct tape for six days. Then soak it in water and gently remove dead tissue with a pumice stone or disposable emery board. Leave the wart exposed for about 12 hours, and then repeat the process until the wart is gone.

  Study results have been mixed on the effectiveness of duct tape in removing warts, either alone or with other therapies.

You'll likely start by seeing your primary care doctor. But you may be referred to a specialist in disorders of the skin (dermatologist). The following tips can help you prepare for your appointment.

What you can do

Bring a list of all medications you take regularly — including over-the-counter (nonprescription) medications and dietary supplements — and the daily dosage of each.

You may also want to list questions for your doctor, such as:

• What made the warts develop?
• If I have them removed, will they come back?
• What types of treatments are available to remove the warts, and which do you recommend?
• What types of side effects can I expect?
• What are the alternatives to the primary approach you're suggesting?
• If the growths aren't warts, what tests do you need to do?
• How can I prevent warts?

What to expect from your doctor

Your doctor may also have some questions for you, such as:

• When did you first notice the warts?
• Have you ever had them in the past?
• Are you bothered by the warts, either for cosmetic reasons or for comfort?
• What treatments have you already used for your warts? If so, how long have you used them and what were the results?