Liquid nitrogen is a very cold, liquid gas used to remove different kinds of skin lesions, such as warts and actinic keratoses. The liquid nitrogen forms an ice ball inside the treated skin. Within 30 minutes after the ice thaws, the treated skin containing the abnormal cells (for example, wart cells) will separate from the normal skin cells.

A stinging or “burning” sensation can be felt during the freezing. This mild pain usually lasts for three to ten minutes while the ice ball thaws. Occasionally, a throbbing sensation may be felt for one or two hours after freezing. This throbbing is most common on fingers, toes, eyelids and lips.
Redness and swelling usually happens within minutes after the freezing. It is also likely that a blister will form 12 to 48 hours after the freezing. The blister may be filled with a clear fluid or with blood, which will give it a blue or violet color. The blister will flatten by itself in three to ten days. If a blister becomes painful, a sterile needle may be used to puncture the top. The fluid can be removed by gently pressing on the blister site with a clean tissue, being careful to leave the blister top intact. If the blister has been drained, daily cleaning with soap and water is important to prevent infection.
Long-term side effects from liquid nitrogen therapy include hyper- or hypopigmentation (meaning a darker or lighter color of the treated area compared to the surrounding skin). This color change within the skin may or may not decrease over the months following treatment.
Warts treated with liquid nitrogen therapy will often need repeated treatments to be completely removed. This usually requires a visit every month.
When to call your health-care provider
Call your health-care provider if the treated area becomes red, swollen, “warm to touch”, painful, or has drainage (all signs of infection) more than one week after freezing.
If you have any other questions or concerns, please call your healthcare provider.