What Causes Warts?

No matter what you might have heard on the playground, touching toads and frogs are not common wart causes.

Warts are caused by the human papillomavirus, or HPV. Researchers have identified over 100 different strains of HPV associated with different skin or mucous membrane problems and modes of transmission.

Not all HPV types cause symptoms and, because everybody's immune system will react to HPV a little differently, it's possible to be carrying HPV and not know it. In addition, because there can be a time lag of weeks or months between the time you're exposed to HPV and the time you develop a wart, it can be hard to determine the specific causes of warts.

The following strains of HPV have been identified as common wart causes:

• Types 1, 4 and sometimes 2: Associated with plantar warts, often found on the feet
• Types 2 and 7: Linked to warts on the hands
• Types 3 and 10: Identified as causes of warts more commonly found on children, these strains gives rise to reddish brown lesions found on the hands and face, called flat warts
• Types 6 and 11: Associated with warts in the genital area.

What Causes Warts to Spread

Although they're caused by HPV, warts are spread by person-to-person contact, or by touching a contaminated surface or object. Between 30 and 40 known HPV strains are spread by sexual contact.

When your skin is damaged, wet or rough, it's much easier to pick up the HPV strains that are common wart causes.

If you have warts, you can spread them to different parts of your body by picking at them, or scratching or biting your nails. If you have a weakened immune system, you may be more likely to get warts, and they can be harder to treat.

Although shaving and not wearing sandals aren't exactly causes of warts, the following practices can help you prevent warts:

• Don't bite your fingernails if you have warts on your hands.
• Don't brush, clip or shave areas where you have warts.
• Don't scratch your warts.
• Don't share towels or shoes with someone who has warts.
• Don't touch someone else's wart.
• Wash hands thoroughly after touching a wart.
• Wear sandals in public showers, locker rooms and swimming pools.

Common Wart Causes Not Associated with Cancer

The HPV strains identified as common wart causes are generally not the strains of HPV associated with cancer. The HPV types that have been linked to cervical cancer, but are not common causes of warts, include:

• HPV 16
• HPV 18
• HPV 31
• HPV 45.

If you've been infected with an HPV strain identified as one of the common causes of warts, it does not put you at an increased risk for HPV-related cancer.

Resources

Healthcommunities.com. (2007). Overview, incidence and prevalence. Retrieved June 1, 2010, from: http://www.podiatrychannel.com/plantarwarts/cause.shtml.

Mayo Clinic. (2010). Causes.Retrieved June 1, 2010, from: http://www.mayoclinic.com/health/common-warts/DS00370/DSECTION=causes.

Nordqvist, C. (2009). What are warts? What causes warts? Retrieved June 1, 2010, from: http://www.medicalnewstoday.com/articles/155039.php.

Stoppler, M. (2006). Warts-a common infectious disease. Retrieved June 1, 2010, from: http://www.medicinenet.com/script/main/art.asp?articlekey=46499.