What Happens When the Dermatologist Freezes Skin?

When a dermatologist aims a canister of liquid nitrogen at your skin and pulls the trigger, the targeted tissue plunges to extreme sub-zero temperatures within seconds, cold enough to destroy abnormal or unwanted cells while leaving the surrounding healthy tissue largely intact. The procedure, called cryotherapy or cryosurgery, is one of the most common in-office dermatology treatments, used on everything from warts and precancerous spots to certain skin cancers. It looks deceptively simple from the patient’s chair, but the biology of what happens beneath the skin’s surface during and after that brief blast of cold is surprisingly complex.

How Cold the Skin Actually Gets

Liquid nitrogen, the most widely used cryogen in dermatology, boils at about −196 °C. When sprayed onto skin or applied with a cotton-tipped probe, it can drop the skin’s surface temperature to around −60 °C within just five seconds of contact.¹ The treated spot then gradually warms back up, crossing 0 °C after roughly 70 seconds.¹ That might sound like it all happens fast, and it does from the patient’s perspective. The actual spray or contact time for a common wart or sun spot is often just a handful of seconds, though the dermatologist may extend it for thicker or more serious lesions.

What you feel during those seconds is an intense, stinging cold. Most people describe it as a sharp burning sensation that peaks during the spray and fades quickly once the nitrogen is removed. For small benign lesions, anesthesia is usually unnecessary. For larger areas or deeper freezes, a local anesthetic may be offered beforehand.

What Happens Inside the Tissue

The damage from cryotherapy unfolds in stages, not all at once. The initial freeze forms ice crystals inside and around the cells. As the temperature drops rapidly, water inside cells freezes, and these intracellular ice crystals physically puncture cell membranes. Meanwhile, the frozen tissue’s tiny blood vessels constrict and then clot, cutting off the oxygen supply to the treated area. Some cells die immediately from this direct trauma.

But a significant portion of the destruction happens later, over the hours and days following treatment. Inflammation floods the area as the immune system responds to the damaged tissue. Cells that survived the initial freeze may still die through apoptosis, a controlled self-destruction process triggered by the injury. Research has shown that tissue destruction from cryotherapy results not only from direct cell death and blood vessel damage during the freeze, but also from the inflammatory response and subsequent apoptosis that follow.² This delayed wave of damage is why the treated spot often looks worse a day or two after treatment than it did immediately afterward.

Why the Thaw Matters as Much as the Freeze

One of the counterintuitive aspects of cryotherapy is that letting the tissue thaw slowly actually increases the damage to targeted cells. During a slow thaw, ice crystals have time to grow larger, creating shearing forces that tear through tissue structures. The concentration of dissolved substances inside cells also rises to toxic levels as ice melts unevenly. Experimental work has confirmed that slow thawing is a prime destructive factor, and that rapid warming, by contrast, increases the chance of cell survival.³

This is why dermatologists treating more aggressive lesions will often use a “freeze-thaw-freeze” technique: they spray the area, let it thaw completely on its own (no warming), and then freeze it again. Each cycle compounds the damage to the targeted cells. The optimal approach for destroying unwanted tissue is fast freezing to a sufficiently low temperature, slow thawing, and repetition of the cycle.³ For a simple wart, a single cycle may suffice. For a skin cancer, two or even three cycles are common.

What Cryotherapy Treats

The list of conditions treated with cryotherapy is long, which partly explains why liquid nitrogen canisters are a fixture in nearly every dermatology office. The most frequent targets include common warts, seborrheic keratoses (those brown, waxy “age spots” that seem to appear out of nowhere in middle age), skin tags, and actinic keratoses, which are rough, scaly precancerous patches caused by years of sun exposure. Among destructive procedures for actinic keratoses, cryotherapy is considered a standard first-line approach for individual lesions.⁴

Cryotherapy is also used for certain skin cancers, particularly basal cell carcinoma. In older patients who may not be good candidates for surgery, studies have reported cure rates of around 95% for basal cell carcinomas treated with cryotherapy.⁵ For superficial basal cell carcinomas on the trunk, even a single freeze-thaw cycle has achieved cure rates above 95%.⁶ These numbers make cryotherapy a genuinely effective option, though it is typically reserved for lower-risk tumors and patients for whom surgical excision poses challenges.

Some dermatologists also combine cryotherapy with topical medications. For Bowen’s disease (squamous cell carcinoma in situ) and superficial basal cell carcinoma, a combination of cryosurgery followed by immediate application of 5-fluorouracil cream has been studied, with clearance rates of about 90% for Bowen’s disease and 87% for superficial basal cell carcinoma at six months.⁷

What to Expect in the Days After

The healing timeline after cryotherapy depends on how aggressively the area was frozen. For a light freeze on a small wart, you might see mild redness and swelling that resolves within a week. For a deeper freeze, the progression is more dramatic and follows a fairly predictable pattern.

Within hours, the treated area reddens and swells. A blister often forms within the first day or two, sometimes filled with clear fluid, sometimes with blood-tinged fluid (which looks alarming but is normal). The blister may be quite large relative to the original lesion. Over the following week, the blister dries into a crust or scab. Underneath, new skin is forming. The scab eventually falls off on its own, usually within one to three weeks for superficial treatments and potentially longer for deeper ones.

Pain is generally mild to moderate. The stinging sensation from the procedure itself fades within minutes, but the area may throb or ache for a few hours afterward, similar to a mild burn. Over-the-counter pain relievers handle it for most people. The treated spot may weep or ooze slightly, and keeping it clean and covered with a simple bandage is usually all the wound care required.

Pigment Changes and Why They Happen

One of the most common and sometimes persistent side effects of cryotherapy is a change in skin color at the treatment site. Studies have found that all frozen lesions develop some degree of hypopigmentation (lighter skin) with a surrounding rim of hyperpigmentation (darker skin), and these pigment abnormalities can persist for at least six months.⁸ For lighter-skinned individuals, this pale spot may be barely noticeable. For people with darker skin, the contrast can be significant and distressing.

The reason lies in the cold-sensitivity of melanocytes, the cells that produce skin pigment. Melanocytes are more vulnerable to freezing injury than the surrounding keratinocytes (the cells that form the bulk of the skin’s outer layer). Research has confirmed that cold exposure can selectively destroy melanocytes while sparing keratinocytes.⁹ After a brief freeze, hypopigmentation can persist even when functional melanocytes are still present in the area, suggesting that the pigment-producing machinery inside the cells is disrupted even when the cells themselves survive. After prolonged freezes, melanocytes may be present but fail to transfer pigment to surrounding cells.⁸

This pigment vulnerability has practical consequences. Dermatologists treating patients with darker skin tones tend to use cryotherapy more cautiously or opt for alternative treatments when possible, because the resulting light spot may be more cosmetically troubling than the original lesion. When cryotherapy is used, shorter freeze times and fewer cycles reduce, but do not eliminate, the risk of lasting pigment change. In a comparison of cryotherapy versus imiquimod cream for actinic keratoses, over half of cryotherapy patients developed hypopigmentation compared to about a quarter of those treated with imiquimod.¹⁰

How Cryotherapy Compares to Alternatives

For precancerous actinic keratoses, cryotherapy remains a workhorse treatment, but it is not always the best cosmetic choice. In a head-to-head trial, cryotherapy cleared about 85% of actinic keratosis lesions compared to about 67% for imiquimod cream.¹⁰ Cryotherapy wins on raw clearance. But among the lesions that did clear, the cosmetic outcome was rated excellent in 82% of cryotherapy-treated spots versus 100% of imiquimod-treated spots. Cryotherapy also produced more blistering, redness, scaling, and scabbing.¹⁰

The tradeoff is fairly clear: cryotherapy is faster (one office visit, done in seconds) and more effective at clearing individual spots. Topical treatments like imiquimod take weeks of at-home application but leave the skin looking better afterward and can treat broader areas of sun damage that may harbor invisible precancerous changes. For someone with a single rough spot on their arm, cryotherapy is efficient and effective. For someone with a field of sun damage across their forehead, a topical approach or photodynamic therapy may treat the whole zone rather than playing whack-a-mole with individual spots.

Who Should Not Have Cryotherapy

Cryotherapy is safe for the vast majority of people, but a few conditions make it risky or inappropriate. Physicians should be aware of contraindications including cold urticaria (a condition where the skin breaks out in hives in response to cold), cryoglobulinemia (abnormal proteins in the blood that clump in cold temperatures), Raynaud’s disease (exaggerated blood vessel spasm in response to cold), and certain connective tissue diseases.¹¹ People with these conditions could experience severe local reactions, impaired wound healing, or systemic flare-ups from the cold exposure.

Location on the body matters too. Areas with poor blood circulation, such as the lower legs in people with diabetes or peripheral vascular disease, heal more slowly and are more prone to complications like ulceration. Cryotherapy on the scalp or near hair-bearing areas can destroy hair follicles, leading to a permanent bald patch. On the fingers and toes, aggressive freezing near nerves can cause prolonged numbness. Dermatologists weigh all of these factors when deciding whether cryotherapy is the right choice or whether a different approach makes more sense.

Cryotherapy for Scars and Keloids

Beyond warts and skin cancers, cryotherapy has carved out a niche in treating hypertrophic scars and keloids, those thick, raised scars that grow beyond the boundaries of the original wound. Standard surface cryotherapy can flatten scars, but the more innovative approach is intralesional cryotherapy, where a needle-like probe is inserted directly into the scar tissue and the freeze is delivered from the inside out. This method freezes a larger volume of the deep scar material than surface spraying can reach, meaning fewer treatment sessions are needed.¹²

Keloids are notoriously stubborn. They recur after surgical excision at frustratingly high rates. Intralesional cryotherapy offers an alternative that destroys the excess collagen from within, causing the scar to gradually shrink and soften over multiple sessions. The tradeoff, again, is pigment change. On keloid-prone skin, which is more common in people with darker skin tones, the resulting hypopigmentation at the treatment site may be conspicuous. Still, for large or painful keloids that have resisted other treatments, it represents a meaningful option.

The Immune System’s Response to Freezing

An area of active research involves what happens immunologically when tissue is frozen and left in place. Unlike surgical excision, which removes tissue entirely, cryotherapy destroys cells but leaves them where they are. As the dead and dying cells break apart, they release their internal contents into the surrounding tissue, essentially exposing the immune system to a concentrated dose of cellular debris. When the frozen tissue is a tumor, this debris includes tumor-specific proteins that the immune system can learn to recognize.¹³

This phenomenon has generated interest in combining cryotherapy with immunotherapy for cancer treatment. The idea is that freezing a tumor creates a kind of in-body vaccine: the destroyed tumor cells teach nearby immune cells what the cancer looks like, potentially generating anti-tumor immune responses that could target cancer cells elsewhere in the body.¹³ This is still largely in the realm of ongoing research rather than routine clinical practice for skin cancer, but it speaks to how much more is happening during a freeze than simple tissue destruction. The same immune activation that helps fight tumors is also responsible for the redness, swelling, and tenderness you feel in the days after a routine cryotherapy session on a wart or sun spot.

Why Melanocyte Sensitivity Is Being Studied on Its Own

The fact that melanocytes are more cold-sensitive than surrounding skin cells, which is the source of the unwanted pigment changes described earlier, is also being explored as a potential therapeutic tool. Researchers have investigated whether carefully controlled cold exposure could selectively destroy melanocytes in conditions characterized by excess pigmentation, such as certain types of dark spots or melasma, while leaving the rest of the skin intact.⁹ The concept, sometimes called selective cryolysis, aims to find the precise temperature and duration that kills melanocytes without harming keratinocytes.

The research is still early, and clinical devices designed for this purpose are not yet widespread. But the underlying principle is a good example of how a side effect in one context becomes a treatment goal in another. The same melanocyte vulnerability that makes cryotherapy cosmetically tricky for dark-skinned patients with warts could, if harnessed precisely, offer a new approach to pigmentary disorders that are currently difficult to treat.

1
PubMed. Skin thermal recovery following cryotherapy: a comparison of liquid nitrogen and liquid nitrous oxide
2
PubMed. Apoptosis and leucocyte-endothelium interactions contribute to the delayed effects of cryotherapy on tumours in vivo
3
PubMed Central. Experimental Cryosurgery Investigations In Vivo – Section: The Thawing Rate
4
PubMed Central. Cryotherapy for Actinic Keratosis: Basic Principles and Literature Review
5
PubMed Central. Cryotherapy as an Effective therapeutic Option in Patients with Nodular Basal Cell Carcinoma – Case Report
6
PubMed. Cryosurgery in the treatment of basal cell carcinoma. Assessment of one and two freeze-thaw cycle schedules
7
PubMed. Cryosurgery and 5-Fluorouracil Combination Therapy for Treatment of Bowen’s Disease and Superficial Basal Cell Carcinoma
8
PubMed. Pigment changes in human skin after cryotherapy
9
PubMed. Selective Cryolysis of Melanocytes: Critical Temperature and Exposure Time to Induce Selective Pigmentary Loss in Yucatan Pig Skin
10
Journal of Drugs in Dermatology. A Comparison of Cryotherapy and Imiquimod for Treatment of Actinic Keratoses: Lesion Clearance, Safety, and Skin Quality Outcomes
11
Indian Journal of Dermatology, Venereology and Leprology. Guidelines for cryotherapy
12
PubMed. Intralesional cryotherapy for enhancing the involution of hypertrophic scars and keloids
13
PubMed Central. Cryoablation and Immunotherapy: An Enthralling Synergy to Confront the Tumors