Dermatologists frequently use cryotherapy, or cryosurgery, a standard, effective method for treating numerous skin lesions. This procedure involves applying extreme cold to destroy abnormal tissue on the skin’s surface. The simplicity and speed of the treatment make it a popular choice for in-office dermatological care. By inducing a controlled cold injury, the procedure targets unwanted cells while minimizing disruption to the surrounding healthy skin. Destruction is achieved through rapid freezing and subsequent thawing.
The Mechanism of Cell Destruction
The goal of cryotherapy is to cause controlled cellular necrosis (cell death) by subjecting the target tissue to intensely cold temperatures. Liquid nitrogen is the most common cryogen used, with a boiling point of approximately -196°C (-321°F), allowing for the rapid removal of heat from the skin. This rapid cooling initiates destruction primarily through the formation of ice crystals.
Immediate freezing causes water inside the targeted cells to crystalize, mechanically rupturing the cell membranes and disrupting internal cellular structures. A rapid freeze followed by a slower thaw is often employed because thawing causes further damage. As ice crystals outside the cells melt, the extracellular environment changes, leading to osmotic stress that draws water back into the damaged cells, causing them to swell and burst.
Beyond direct cellular injury, a secondary mechanism involves the circulatory system. Extreme cold causes blood vessels and capillaries in the frozen area to constrict and become damaged, leading to vascular stasis. This disruption halts blood flow, starving the targeted tissue of oxygen and nutrients, which results in ischemic necrosis. The combination of mechanical cell rupture and vascular shutdown ensures destruction of the treated lesion.
Conditions Successfully Treated By Freezing
Cryotherapy is versatile, offering a non-invasive treatment option for a wide spectrum of skin growths, from benign cosmetic issues to precancerous lesions. The most frequent application is treating actinic keratoses, which are rough, scaly patches developing after years of sun exposure. These lesions are considered premalignant, potentially progressing into squamous cell carcinoma, and their removal is a common preventative measure. A single, short freeze-thaw cycle is sufficient for these superficial lesions.
Viral lesions are also commonly addressed with cryosurgery, particularly common warts caused by the Human Papillomavirus. Warts often require a more aggressive approach, sometimes needing longer freeze times or multiple treatment sessions spaced several weeks apart due to their resistance and depth. Complete cure rates vary but can reach approximately 75 percent, depending on the size and location.
The procedure is effective for managing common benign skin growths that are not medically threatening yet may be bothersome. Seborrheic keratoses, which are harmless, waxy, “stuck-on” looking lesions, are readily treated with cryotherapy. Similarly, skin tags, small flaps of tissue appearing in areas of friction, can be quickly removed using this technique. The sensitivity of melanocytes to cold also makes cryotherapy useful for treating solar lentigines (sun spots or age spots), though this carries a risk of hypopigmentation.
Patient Experience and Recovery
During liquid nitrogen application, patients typically feel an intense cold sensation immediately, which quickly transitions into stinging or burning discomfort. This sensation is usually brief, lasting less than a minute, and often does not require local anesthesia for small, isolated spots. For lesions on sensitive areas (e.g., the forehead), a throbbing sensation may persist after the procedure.
The treated area shows immediate signs of inflammation, including redness and swelling, as the body begins healing. Within hours to a day, a blister typically forms over the site of the destroyed tissue. This blister may be clear and fluid-filled, or hemorrhagic, appearing dark red or purple, especially on the hands or feet, as a consequence of the vascular damage.
Patients should avoid rupturing the blister, as the overlying skin acts as a protective, sterile dressing. The blister eventually flattens and dries out, forming a crust or scab over the damaged area. Healing time varies depending on the depth of the freeze and the location on the body, but most sites scab over within a week. The scab naturally falls off, revealing new, healed skin underneath, usually within one to three weeks.