If you have an active wart, that means that your immune system doesn’t detect the wart, allowing it to grow undisturbed. Your immune system is usually usually capable of defeating a wart. Inflaming the surrounding tissue can initiate an immune response to the wart, which ultimately kills it. Destroying/damaging much of the wart itself gives it a big boost too.
The liquid nitrogen causes frostbite and irritates and/or kills tissue in the area. They can also do this with acid or burning, but liquid nitrogen is relatively quick, safe, and less painful.
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