If you have warts, you know they can be embarrassing, especially on your face and hands. Sometimes they itch or hurt, especially on the soles of your feet, but they are usually harmless. When you know what causes them, you may be able to avoid getting them or re-acquiring them after you have them removed. A virus called the human papillomavirus, HPV, causes the pea-sized skin growths. Infected skin cells produce excess, hardened protein nodules, which become warts.
Common Warts
Scientists at the National Cancer Institute say there are more than 100 related strains of HPVs. A common wart is a papilloma, or a benign, noncancerous tumor. The HPVs that cause typical or common hand and foot warts are of a different strain than those that produce growths in the throat, the genital area or the feet. Some HPVs appear to be oncogenic or carcinogenic, meaning they cause certain types of cancer. They are called high-risk HPVs.
Genital Warts
Sexual transmission spreads a different type of wart, produced by some of the more than 30 types of genital HPVs. Most genital HPV infections produce few or no warts or symptoms. Some infections persist for many years in women without causing abnormalities but increase their risk of developing cervical cancer. Genital warts, medically called condylomata acuminata, are most often caused by two of the 30 genital HPV sub-types, HPV--6 and HPV--11. Warts may appear from several weeks to years after contact, causing characteristic flat growths rather than the more typical raised, common skin warts.
Plantar Warts
Plantar warts grow on the soles of your feet. Your weight forces them to grow inward, making plantar warts unusual in that they usually cause pain. When you walk, the warts press upward into the muscles of your foot. Mayo Clinic doctors report that the particular variety of HPV that causes plantar warts is not highly contagious. It thrives in moist, warm environments, such as shower floors, public swimming areas and locker rooms. You can contract the virus when you walk barefoot in these places. Plantar HPV is communicable between people by contact with skin cells shed from a wart or by contact with blood from an injured wart. You can spread the virus from one of your feet to the other by scratching it.
Susceptibility
Contact with HPV will not cause warts with the same likelihood in everyone exposed to the virus. People in the same family do not always react to HPV in the same way. Parents and children will not necessarily spread warts to each other when they share the same shower.
