What should you know about liquid nitrogen and water?

Liquid nitrogen is far colder than water, so heat moves quickly from the water into the cryogen. The nitrogen changes into gas and may appear to bubble, fog, or surge across the surface. A small amount can seem to disappear quickly, but that does not make contact harmless: droplets or trapped liquid can freeze tissue before they evaporate.

In dermatology, the same heat-transfer principle allows a clinician to freeze a selected lesion. The operator chooses the application method and observes the skin response. Water, wet dressings, or moisture around the treatment site can change how cold is delivered, so follow the clinic's instructions rather than experimenting with the reaction.

Never mix liquid nitrogen with water in a closed container, carry it in an unsuitable vessel, or use it as a home skin treatment. If skin is exposed, move away from the source, remove contaminated jewellery or clothing if it is not frozen to the skin, and warm the area gradually with lukewarm water. Do not rub, scrub, or use direct heat.

A clinic may advise how to wash and dress a treated area after cryotherapy. A blister or crust can occur as frozen tissue separates from healthy skin. Protect the area from friction and follow the stated wound-care plan.

Get prompt medical help for numb, pale, hard, or severely painful skin after contact, especially if a blister is extensive or the exposed area involves the face, hands, feet, or genitals. Emergency help is needed for breathing trouble, eye exposure, or symptoms suggesting low oxygen in an enclosed space.

Ask how the treatment area should be kept clean, whether moisture affects the dressing, and which changes mean the wound needs an examination.