Warts are small growths caused by the human papilloma viruses (HPV) of which there are at least 60 different known strains.
They can appear singly or in clusters and are most common on the hands, fingers, elbows, forearms, knees, face and the skin around the nails. Usually, they occur on skin that is continually exposed to friction, trauma or abrasion.
A wart is a highly contagious virus and hence warts can easily spread to other parts of the body where there is a break in the skin. In men, a wart on the face, for example, can be spread by shaving nicks.