Warts are growths on the skin that occur in response to a viral infection.

Warts come from the human papilloma virus, or from one of its 48 different subtypes, and enter the skin by direct contact. They thrive in moist environments but can occur anywhere.

Once on the skin these viruses develop into nodules, usually gray-colored, benign protuberances that are highly contagious and easily spread by skin contact. Some warts will disappear over time if the immune system recognizes it as a virus and...