Cryotherapy

What is cryotherapy?

Cryotherapy refers to a treatment in which surface skin lesions are frozen.

Cryogens used to freeze skin lesions include:

• Liquid nitrogen (the most common method used by doctors, temperature –196°C)
• Carbon dioxide snow (more commonly used 20 years ago, –78.5°C) 
• Dimethyl ether and propane or DMEP (available over the counter, –57°C).

Spray gun

Dewar flask

Dewar flask safety

Skin lesions treated with cryotherapy

Lesions that may be treated by cryotherapy include:

• Actinic keratoses
• Viral warts
• Seborrhoeic keratoses (senile warts).

Specialist dermatologists sometimes freeze small skin cancers such as superficial basal cell and in situ squamous cell carcinoma (intraepidermal carcinoma), but this is not always successful, so careful follow-up is necessary.

Freezing may be the most suitable way of getting rid of many different kinds of surface skin lesion. It is relatively inexpensive, safe, and reliable. However, it is important that the skin lesion has been properly diagnosed. It should not be used to treat melanoma or any undiagnosed pigmented lesion that could be melanoma.

The treatment

Cryotherapy stings and may be painful, at the time and for a variable period afterwards. 

Liquid nitrogen

Cryotherapy using liquid nitrogen involves the use of a cryospray, cryoprobe or a cotton-tipped applicator. The nitrogen is applied to the skin lesion for a few seconds or longer, depending on the type of lesion and the diameter and the depth of freeze. The treatment is repeated in some cases, once thawing has completed. This is known as a ‘double freeze-thaw’.

Swabs

Spray gun

Spraying viral warts

Carbon dioxide snow

Carbon dioxide cryotherapy involves making a cylinder of frozen carbon dioxide snow or a slush combined with acetone. It is applied directly to the skin lesion.

DMEP

DMEP comes in an aerosol can available over the counter. It is used to treat warts using a foam applicator pushed onto the skin lesion for between 10 and 40 seconds, depending on its size and site.

Ice ball

Immediate swelling

Looking after the treatment area

Immediate swelling and redness may be reduced by applying a topical steroid on a single occasion straight after freezing. Aspirin orally may also reduce the inflammation and discomfort.

The treated area is likely to blister within a few hours, depending on the depth and duration of the freeze. Sometimes the blister contains clear fluid and sometimes it is red or purple because of bleeding (this is harmless). Treatment near the eye may result in a puffy eyelid, especially the following morning, but the swelling settles within a few days. Within a few days, a scab forms and the blister gradually dries up.

Usually, no special attention is needed during the healing phase. The treated area may be gently washed once or twice daily and should be kept clean. A dressing is optional but is advisable if the affected area is subject to trauma or clothes rub on it.

When the blister dries to a scab, apply petroleum jelly and avoid picking at the scab. The scab peels off after 5–10 days on the face and 3 weeks on the hand. A sore or scab may persist as long as 3 months on the lower leg because healing in this site is often slow.

Haemorrhagic blisters

Clear and haemorrhagic blisters

Eyelid swelling

Results of cryotherapy

After a standard freeze of actinic keratosis, seborrhoeic keratosis, or viral wart, the skin may appear entirely normal without any sign of the original skin lesion. It may take several treatments to achiev.e this

Complications of cryotherapy

The main concern is secondary wound infection, but this is uncommon. Infection may cause increased pain, swelling, thick yellow blister fluid, purulent discharge and/or redness around the treated area. Consult your doctor if you are concerned: topical antiseptics and/or oral antibiotics may be necessary.

Other undesirable effects may include:

• Delayed healing and ulceration
• Local nerve damage (usually temporary)
• Permanent hypopigmentation or scar
• Persistent or recurrent skin lesions, necessitating further cryotherapy, surgery or other treatment.

Prolonged healing

Secondary infection

Recurrent basal cell carcinoma