Cryotherapy for skin diseases has a history of nearly 50 years, initially with carbon dioxide snow (dry ice), and now with liquid nitrogen. The cryogenic temperature of liquid nitrogen is -196 degrees Celsius, which is used to treat skin diseases by producing low temperature effects on skin lesions through various cryotherapy devices. It is commonly used to treat a variety of proliferative skin diseases, such as: small area of hemangioma, nodular itchy rash, seborrheic keratosis, sweat duct tumor, various moles and warts and other skin growths, but also can be used to treat baldness, neurodermatitis, etc. For smooth pigmented nevi with no recent itching or growth, sufficient freezing depth should be ensured during cryotherapy to achieve complete freezing off, otherwise, freezing stimulation may easily lead to malignant transformation of nevus cells. For lesions suspected to be skin malignant tumors, cryotherapy should not be used as much as possible, but should be completely excised and examined by histopathology and, if necessary, immunohistochemistry. If the blister is small, it can be absorbed by itself. If it is large or painful, you can puncture it with a sterile needle from the base of the blister, use a cotton swab to drive out the blister fluid, and apply iodophor locally to prevent infection. Generally two weeks to three weeks after the scabs fall off, the wound surface is smooth and flat. When the blister dries up and starts to scab, protect the scab and leave it to fall off on its own. If the scab is accidentally rubbed off in advance, there is a risk of pigmentation or leftover wounds scabbing again, or even secondary infection.