In contrast to Swift, which is a thermal treatment, cryotherapy involves cooling the lesion rapidly using nitrous oxide to -89 degrees centigrade. Similar to the Swift treatment, the wart has its overlying callus carefully pared away initially before freezing. This method is not always suitable for multiple lesions, nor so effective for lesions on the sole of the foot where the skin is at its thickest.
This treatment is the most superficial and is more suitable for the very youngest of patients. Silver nitrate is caustic when applied to the skin, and may sting slightly initially although this is usually as bad as it gets. The skin turns black, and the top layer eventually flakes away naturally or is abraded by fine grade sandpaper. Due to the superficial nature of the treatment multiple visits to the clinic over a short period of time are to be expected.