What Are Warts Caused By?

What are warts? 

Warts are small skin growths that are usually harmless and that are caused by the human papillomavirus.
Warts are small skin growths that are usually harmless and that are caused by the human papillomavirus.

Warts are small skin growths and are usually painless and harmless. Warts are benign (non-cancerous) and caused by a virus called human papillomavirus (HPV) and so they are highly contagious. Warts can be rough to the touch or may also be flat and smooth.

Most are the same color as your skin, but sometimes they are dark brown or gray and can have black, seed-like dots.

Signs and symptoms of warts

Warts do not cause any other symptoms aside from the growths themselves. If warts appear in places like the hands, they can be painful and bleed if bumped. Warts begin to develop months before you ever see them on the surface of your skin. 

Types of warts

Common warts

These are rough to the touch and gray or brown. They are most often on your fingers, elbows, knees, or face.

Plantar and palmar warts 

These warts grow on the soles of your feet or the palms of your hands. Plantar warts may grow in clusters called mosaics and can be very painful.

Flat warts

These are small and smooth, and most often appear on your face.

Filiform warts

Usually on your eyelids, lips, face, or neck, these warts are long and narrow.

Periungual warts

These warts grow around the edges of your fingernails as thick skin. They can crack, bleed, and be painful. 

Genital warts

When HPV is spread through sexual contact you can develop warts on your genitals.

What causes warts?

HPV is a virus that occurs naturally and has more than 40 variations. Anyone can have HPV and most adults will contract some version of the virus during their life.

Warts spread very easily through direct contact with HPV. Your warts may spread by touching another part of your body. You can also contract the virus from sharing personal items like towels and razors.  


How are warts diagnosed?

Your doctor will complete a physical exam to diagnose warts based on their appearance. They will usually diagnose warts based on their appearance but may also use a small blade to scrape away the top layers of the wart to assess its texture. Many warts have black dots beneath the top layers. These are tiny, clotted blood vessels. 

For persistent warts, you may need to see a dermatologist for specialized treatment. In some cases, your dermatologist takes a sample of the wart and completes a biopsy.

Treatments for warts

There are many treatments for warts, and some can be done at home. Always talk to your doctor about your condition before beginning treatment. Your doctor may suggest leaving warts alone until they go away on their own.

Some warts can be hard to get rid of because the thick layers of skin make it hard for the medicine to reach the virus that causes them. If you try an over-the-counter treatment and warts grow back, talk to your doctor about other options. 

Common treatments for warts include:

  • Topical treatments – These may be purchased at your local store or prescribed in a higher strength by your doctor. Topical treatments contain acid that removes the dead skin cells on the wart, causing it to go away.
  • Cryosurgery – Your doctor uses a special chemical like liquid nitrogen to freeze the wart. This treatment is usually repeated several times.
  • Laser treatment – This is used for stubborn warts that won’t go away with other treatments. Your doctor will cut the wart away using a laser tool that goes deeper in the skin to remove more of the wart than topical treatments can.
  • Medication – Genital warts require a special medication used to treat sexually transmitted diseases.

After getting rid of a wart, you will probably want to make sure it doesn’t come back. Since HPV is a virus, you can never get rid of it in your body. You can prevent future wart growth using preventative measures: 

  • Avoid touching another person’s wart(s)
  • Don’t share towels, razors, or shoes
  • Clean and cover open wounds like cuts and scrapes
  • Wash your hands frequently
  • Moisturize to prevent dry, cracked skin
  • Don’t chew or pick at your nails
  • Wear flip-flops around pools, showers, and locker rooms

American Academy of Dermatology Association: "How to heal warts more quickly and prevent new ones."

Dignity Health: "How do you get warts? A quick guide to causes, symptoms, and treatments."

Hopkins Medicine: "Warts in children."

Kids Health: "Warts."

University of Michigan Health: "Warts and plantar warts."

U.S. Department of Health & Human Services: "HPV Human Papillomavirus."