Cryotherapy

Cryotherapy (in dermatology) is a treatment that uses extreme cold to destroy abnormal or unwanted skin tissue.

A very cold substance — most commonly liquid nitrogen — is applied directly to the target area on the skin. The intense cold freezes the cells in that spot. Ice crystals form inside the cells and the blood supply to the area is cut off. The damaged tissue dies, then naturally sheds or peels away over the following days and weeks, leaving the surrounding healthy skin intact.

Dermatologists use cryotherapy to treat a range of skin conditions — both non-cancerous growths and certain early-stage or superficial (surface-level) skin cancers. It is chosen when the lesion (abnormal patch or growth) is clearly visible, well-defined, and accessible on the skin surface.

• Warts (viral growths caused by HPV) on the hands, feet, or body
• Verrucas (plantar warts — warts on the sole of the foot)
• Seborrhoeic keratoses (rough, waxy, non-cancerous skin growths that often appear with age)
• Actinic keratoses (rough, scaly patches caused by years of sun damage that can become cancerous if untreated)
• Skin tags (small, soft flaps of skin that hang off the body)
• Molluscum contagiosum (a viral skin infection that causes small, round bumps)
• Solar lentigines (flat, dark sun spots)
• Superficial basal cell carcinoma (a type of early-stage skin cancer limited to the top layers of skin)
• Bowen's disease (squamous cell carcinoma in situ — an early form of skin cancer that has not yet spread deeper)

Cryotherapy is not suitable for every situation. A dermatologist will usually advise against it in the following cases:

• Lesions in areas where freezing could damage nearby nerves, tendons, or vessels (for example, around the eyes or over major joints)
• Patients with cold-related conditions such as cold urticaria (an allergic skin reaction to cold) or Raynaud's phenomenon (a condition in which cold causes blood vessels to narrow severely)
• Patients on blood thinners, as the treated area may bleed more easily
• Dark or brown skin tones, because freezing can cause permanent pale patches (loss of pigment) in those areas
• Thick or deep lesions that extend well below the skin surface — surgery or another method may be more effective
• Lesions that have not yet been diagnosed — a biopsy (tissue sample test) is usually needed first

Dermatological cryotherapy is generally a low-risk procedure when performed on suitable lesions, but the following reactions and complications are recognised:

• Pain or stinging during and immediately after freezing — this is expected and usually brief
• Redness and swelling around the treated spot, which is a normal response and typically settles within a few days
• Blister formation (a fluid-filled bubble under the skin) over the treated area — this is common and part of how the skin heals
• Temporary darkening (hyperpigmentation) or permanent lightening (hypopigmentation) of the treated skin, more noticeable in people with darker skin tones
• Scarring, particularly if the freezing was deep, prolonged, or the area was large
• Hair loss in the treated area if hair follicles were frozen
• Numbness or altered skin sensation near the treated site, usually temporary
• Nerve injury causing lasting numbness or tingling, in rare cases when treatment is performed close to a nerve
• Infection of the treated area if the wound is not kept clean
• Treatment failure — the lesion may not fully respond, especially for thick warts, and a repeat session may be needed

Preparation for dermatological cryotherapy is generally simple. There is no fasting required. However, the dermatologist will usually ask about your current medications, especially blood thinners, as these can increase bleeding or bruising at the treated site. Patients are generally advised to inform their doctor about any cold-sensitivity conditions before the appointment.

Before the procedure, the dermatologist may carry out one or more of the following:

• A visual skin examination of the lesion to confirm it is suitable for cryotherapy
• A dermoscopy (a detailed examination using a magnifying device with a light) to look more closely at the lesion's structure
• A biopsy (tissue sample test) if the diagnosis is uncertain — cryotherapy will usually only proceed once the results are known
• A discussion about your skin tone, as darker skin carries a higher chance of pigment changes after treatment

The procedure itself is typically performed in an outpatient clinic and takes only a few minutes per lesion. Here is what usually happens, in order:

• 1. The skin around the lesion is cleaned.
• 2. The dermatologist may apply a numbing cream or give a small local anaesthetic (pain-blocking) injection to the area, particularly for larger or more sensitive lesions.
• 3. Liquid nitrogen is applied to the lesion using a spray device or a cotton swab, depending on the size and location.
• 4. The area is frozen for a set number of seconds. The doctor controls the depth and duration carefully.
• 5. The area is allowed to thaw naturally. In some cases, a second freeze-thaw cycle is performed during the same session for more complete treatment.
• 6. The treated area is checked, and the patient is given aftercare instructions before leaving.

Recovery after cryotherapy takes place at home. Because cryotherapy is an outpatient procedure, patients leave the clinic on the same day. The treated area will go through a predictable healing process over the days and weeks that follow, and most people can return to normal daily activities right away, with a few precautions.

• Keep the area clean and dry for the first day or two as directed by your dermatologist.
• A blister (fluid-filled bubble) may form over the next day or two — this is normal. It should generally be left intact; your doctor will advise whether it needs to be drained.
• Avoid picking, scratching, or rubbing the treated area, as this can introduce infection or cause scarring.
• If a dressing (wound cover) has been applied, follow the dermatologist's instructions on when and how to change it.
• Sun protection is important: the healing skin is sensitive, and sun exposure can worsen pigment changes. Use a broad-spectrum sunscreen (one that blocks both UVA and UVB rays) on the area once the skin has closed.
• Avoid soaking the area (baths, swimming pools, or the sea) until the skin has fully healed.
• Some discomfort, mild oozing, or crusting (scab formation) over the treated spot is normal in the first one to two weeks.
• The dead tissue will naturally peel or fall away — the time this takes varies depending on the size and depth of the lesion treated.
• A follow-up appointment is usually scheduled so the dermatologist can check whether the lesion has cleared or whether a further session is needed.
• Report to your doctor promptly if you notice spreading redness, increasing pain, pus (thick discharge), or fever, as these may be signs of infection.