Cryotherapy, also known as cryosurgery, is a common dermatological technique involving the controlled application of extreme cold to destroy unwanted or abnormal skin tissue. This minimally invasive, in-office procedure uses a cryogen, most often liquid nitrogen, to achieve sub-zero temperatures at the skin’s surface. The intense cold energy causes cellular destruction, allowing the body to ultimately shed the damaged tissue and replace it with new, healthy skin.
The Science Behind Freezing
The mechanism of tissue destruction involves physical and physiological processes that lead to necrosis, or cell death. Liquid nitrogen, the most common agent, has an extremely low boiling point of approximately -196°C (-321°F), ensuring a rapid transfer of heat away from the targeted skin lesion. This quick heat loss causes the water inside and outside the cells to freeze.
The initial freezing forms ice crystals in the extracellular space. This ice formation concentrates the solutes outside the cell, creating a powerful osmotic gradient that pulls water out of the cells. As the temperature drops further, ice crystals form inside the cells, causing mechanical injury and irreversible damage to cell membranes and internal structures. Maximum tissue destruction is achieved through a rapid freeze followed by a slow, natural thaw, which further enhances cellular damage through osmotic shock and vascular injury. The freezing process also causes local vascular stasis, or blockage of small blood vessels, cutting off the blood supply to the lesion and leading to secondary cell death from lack of oxygen.
Common Conditions Treated
Dermatologists employ cryotherapy to manage a wide spectrum of skin growths, ranging from benign lesions to certain superficial malignancies. It is highly effective for common benign growths such as warts, caused by the human papillomavirus, and molluscum contagiosum. Other frequently treated non-cancerous lesions include skin tags and seborrheic keratoses.
The technique is also a standard treatment for precancerous lesions, specifically actinic keratoses, which are rough, scaly patches resulting from chronic sun exposure. Actinic keratoses are targeted because they carry a risk of transforming into squamous cell carcinoma. In select, low-risk cases, cryotherapy may also be used to treat certain superficial skin cancers, such as early-stage basal cell carcinoma or squamous cell carcinoma in situ. However, using cryotherapy for cancer is highly selective and depends on the tumor’s size, depth, and location.
What Happens During the Procedure
The cryotherapy procedure is typically quick and involves minimal preparation, often requiring just cleaning the treatment area. The dermatologist applies the liquid nitrogen using one of three methods: a spray canister, a cotton-tipped applicator (dipstick), or a cryoprobe. The spray technique, where the liquid nitrogen is directed onto the lesion from a distance of about one to two centimeters, is the most common approach.
Patients immediately feel an intense cold sensation, which progresses to a stinging, burning, or aching feeling as the tissue freezes. The duration of the freeze is precisely controlled, typically lasting five to thirty seconds, depending on the lesion’s size and type. The targeted area turns white as an “ice ball” forms, indicating sufficient temperature drop. For more resistant or deeper lesions, the dermatologist may perform a second freeze-thaw cycle after the tissue returns to near-normal temperature, increasing the destructive effect.
Recovery and Aftercare
Immediately following the application of the cold, the treated area becomes red, swollen, and tender, which is a normal inflammatory response. A blister usually develops within 24 hours; this blister may be clear or filled with blood, especially on the hands or feet. The formation of a blister is a sign that the freezing process successfully targeted the unwanted tissue.
It is important not to puncture or pick at the blister, as the skin acts as a natural sterile dressing, protecting the underlying healing tissue and preventing infection. If the blister bursts naturally, the area should be gently cleaned with mild soap and water and covered with a non-stick bandage or a smear of petroleum jelly. Over the next few days, the blister will dry up, and a dark crust or scab will form.
The scab will naturally fall off as the new skin underneath heals. This process typically takes between one and three weeks, though complete healing can take up to six weeks for deeper treatments. Patients should avoid scratching or picking at the scab to prevent scarring or delayed healing. Taking over-the-counter pain relievers like acetaminophen can help manage mild discomfort in the first 24 hours. Patients should contact their provider if they notice signs of infection, such as increasing pain, severe redness after 48 hours, or the presence of pus.