Warts are caused by the human papillomavirus (HPV). There are more than 100 recognized strains of HPV and, of these, more than 60 are known to cause or contribute to wart formation.
Though they are often unsightly and can be very difficult to treat, warts are benign growths that rarely pose long-term health risks.
Classification
Warts are classified by their location and shape. Plantar warts are often mistakenly referred to as "planter warts," when, in actuality, they take their name from the Latin words, "planta pedis," which means the "sole of the foot." Periungual and subungual warts take their names from the Greek word, "unguis," which means "nail." "Peri" and "sub" refer to the wart's location beside or beneath fingernails and toenails.
Types of Warts on Feet
Plantar warts are one of the most common types of warts on the feet. They can be quite painful and are sometimes mistaken for a corn or callus. Due to their location on the sides and undersides of the feet, and the constant pressure being applied to them, plantar warts tend to grow inward. Unlike other warts, they are often flat and hard. When many plantar warts grow side-by-side, they are called mosaic warts.
The location of periungual and subungual warts makes treating these types of warts very difficult. To effectively treat the affected skin, the nail often has to be removed.
Direct Contact
HPV is transmitted through direct and indirect contact. Direct contact refers to skin-to-skin transmission of the virus. This can be from one person to another, or through self-infection. Self- infection occurs when the virus spreads from one wart to uninfected areas of the body.
The strains of HPV that cause plantar warts are not especially contagious, but they thrive in moist areas. Hot, sweaty feet are a perfect location for the virus to live until it can enter the body at a new location. A tiny cut or an abrasion on the surface of the skin, which is very common on the soles of the feet, especially in people who walk barefoot, is all the entrance the virus needs.
The spread of periungual and subungual warts from an infected finger or toe is common in people who bite or pick at their nails. As long s the skin remains unbroken, HPV infection is rare. Once the skin is damaged, however, the virus can enter the new site.
Indirect Contact
HPV can be transmitted through indirect contact. This occurs when a person touches an object that was previously touched by an infected individual. Because the strains of the virus that cause foot warts flourish in moist environments, locker rooms, communal showers, community pools, spas and saunas are locations where people commonly pick up warts.
Immune Response
The American Academy of Dermatology notes that infection rates vary from person to person and that an individual's immune system plays a role in whether warts will develop or not. Warts tend to develop in people with weakened immune system more so than in healthy individuals.
