Warts are noncancerous skin growths caused by infection with the human papillomavirus (HPV). Many different types of HPV exist that can cause warts to form on the skin or mucous membranes (e.g., mouth, genitals). Warts are usually pink to flesh-colored and have a rough texture, but some have a dark color and a smooth feel.

The major categories of warts include:

• Common warts. Typically appear on the fingers, especially in areas where skin has been broken around the nails and on the back of the hand.
  
  
• Foot warts. Also known as plantar warts, they appear on the soles of the feet at pressure points (such as the balls and heels of the feet).
  
  
• Flat warts. Small, smooth warts that typically grow in large groups of between 20 and 100 warts at a time, most commonly on the face of children and in areas irritated by shaving in adults.
  
  
• Genital warts. Irregular, bumpy growths with the texture of a small cauliflower that are transmitted through sexual contact. They may appear near the genitals and other body areas, and are usually relatively harmless. However, some types may cause abnormalities that can lead to genital cancer.

Warts are contagious, but most only pose a very low risk of being passed to another person through direct or indirect contact. However, genital warts are considerably more contagious than most other types of warts.