Some Warts are easily removed by freezing them (Cryotherapy) with common brand name liquid nitrogen sprays (Cryogun) like Dr Scholls freeze away, Wart remover. Freeze off and Wart off. They work by freezing the wart or warts and can take as little as a single applications to be successful. A little goes a long way and while blasting the wart will kill it off quicker. It can also damage surrounding tissue, less is sometimes more.
This is best applied as soon as the wart is noticed. Old warts can be extra stubborn and may need to be treated with wart killer first and then frozen with liquid nitrogen for a double dose treatment. If is a good idea to remove as much of the wart surface as it dies off. so you hit fresh material.
The wart growth is caused by a virus.