Cryotherapy in Dermatology
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Direct answer
Cryotherapy in dermatology destroys tissue by freezing it, most often with liquid nitrogen at about minus 196 degrees Celsius, and it is used for warts, actinic keratoses and small benign lesions. The freeze must cover a small margin of normal skin, and a double freeze-thaw cycle increases tissue destruction. Its characteristic complication is hypopigmentation, which is especially visible and sometimes permanent in darker skin.
What you must remember
- Agent: liquid nitrogen at about minus 196 degrees Celsius, applied by spray, cotton bud or cryoprobe.
- Commonest indication: cutaneous warts, with actinic keratoses, seborrhoeic keratoses and small benign lesions also treated.
- Margin: a small margin of normal skin is included so that the lesion is fully destroyed.
- Double freeze-thaw: two cycles of freezing and thawing produce greater tissue destruction than a single freeze.
- Hypopigmentation: the most important complication, particularly in Fitzpatrick skin types IV to VI, and it can be permanent.
- Other complications: blistering, pain, scarring and, in sensitive areas such as the nail matrix, injury like frostbite.
- Contraindications: cold urticaria, cryoglobulinaemia and Raynaud phenomenon, plus local neuropathy that impairs sensation.
- Biopsy first: pigmented, changing or uncertain lesions need biopsy before freezing, because freezing can destroy the evidence needed to exclude melanoma.
A step-by-step freeze for a common wart
Cryotherapy is a simple procedure with a small margin for error, so a standard sequence protects the patient and the result. The steps below follow the usual office practice for a benign lesion.
- Select the lesion: confirm that it is benign and treatable, and avoid freezing any pigmented or changing lesion.
- Prepare the patient: explain the expected pain, blistering and temporary pale patch, then record consent.
- Apply the freeze: hold the spray or cotton bud over the lesion, freezing a small margin of normal skin until it whitens.
- Thaw and repeat: allow the tissue to thaw, then repeat the freeze once to complete a double cycle.
- Protect and review: keep the area clean and dry, expect blistering over the next few days, and review at the agreed interval.
- Escalate if the response is poor: combine with a keratolytic or move to another modality for resistant warts.
The procedure is quick, but the risk of pigment loss depends on how much skin is frozen and on the patient's skin type. Shorter freezes and clear counselling reduce the chance of an unwelcome result, especially in darker skin.
Where the exam tries to catch you
Stems test whether you can apply cryotherapy safely and recognise the lesion that must not be frozen.
- Trap: freezing a pigmented lesion without a biopsy. Correct: melanoma must be excluded first, since cryotherapy can destroy the evidence and delay diagnosis.
- Trap: ignoring hypopigmentation risk in darker skin. Correct: hypopigmentation is the characteristic complication, so warn the patient and use cautious freeze times.
- Trap: freezing a patient with cryoglobulinaemia or cold urticaria. Correct: cold-induced disease is a contraindication to cryotherapy.
Frequently asked questions
What temperature does liquid nitrogen reach in cryotherapy?
Liquid nitrogen reaches about minus 196 degrees Celsius, the temperature used in cryotherapy for destroying cutaneous lesions. Freezing intracellular water at this temperature causes cell death when the freeze time is adequate.
Why is a double freeze-thaw cycle used in cryotherapy?
A double freeze-thaw cycle is used because two cycles of freezing and thawing cause greater tissue destruction than a single freeze. It is a standard technique for warts in many dermatology practices.
Which complication of cryotherapy matters most in darker skin?
Hypopigmentation is the most important complication of cryotherapy in darker skin, and it can be permanent. Patients with Fitzpatrick skin types IV to VI need warning in advance and more cautious freeze times.
Which lesions should not be frozen without a biopsy?
Pigmented, changing, bleeding or uncertain lesions should not be frozen without a biopsy, because cryotherapy can destroy the evidence needed to exclude melanoma and other malignancy. Benign warts and clearly identified seborrhoeic keratoses are the typical targets.