Verrucas mainly occur on the heel and the ball of the foot or the underside of the big toe. Corns usually occur between and on top of the toes but occasionally they can also appear on the ball and the heel. The appearance of a wart will have a dry, crusty surface with tiny black dots deep inside while the corn will have a surface which is thick and callused and there will be no black dots. The warts often develop in clusters while corns are always single and may be found in several different areas on the same foot. Plantar warts are often passed on when walking barefooted on communal surfaces such as public swimming pools and showers. They are caused by the human papilloma virus (HPV) and are contagious. Direct contact with the virus can infect your skin through a scratch. The virus then grows inward, causing thickening and damage to the skin and the appearance of warts.
Corns usually appear when a prominent bone in the foot presses against the inside of your shoe. The pressure causes the skin to thicken just at that point making a hard surface. This hard surface then becomes the core of the corn that penetrates deep into the foot. The corn becomes cone-shaped with the point facing inward which in turn presses into the foot cause pain. This can become very uncomfortable and feels as if you are walking with a stone in your shoe. Corns are not contagious but warts are.