Cryotherapy uses extreme cold, applied briefly to a small area, to destroy tissue deliberately. Ice forming inside cells damages them, and the surrounding skin recovers. Its difficulty is depth: too shallow achieves nothing, too deep affects structures nobody wanted to affect.
What does the cold actually do?
It destroys tissue, deliberately, and the mechanism is more interesting than it sounds.
When skin is cooled rapidly enough, ice crystals form inside and around cells. Their formation damages cell membranes directly, and the movement of water that accompanies freezing disturbs the chemistry inside cells further. Thawing does additional damage, which is why a freezing and thawing cycle rather than the cold alone is what matters.
Blood supply to the area is disrupted by the freezing at the same time, and that contributes to the tissue breaking down over the following days.
The treated skin then dies and is shed, and skin regenerates from the edges and from below. That regeneration is the reason the technique works at all: it destroys a defined patch and lets the surrounding tissue rebuild it.
Why is depth the whole difficulty?
Because there is no way to see how far the freezing has travelled while it is travelling.
It propagates downwards and outwards from the point of application, and the clinician is judging depth from experience, from how the surface looks as it freezes, and from how long the application has lasted. Too shallow and nothing useful is achieved. Too deep and structures nobody intended to affect are included in the freezing.
Several things sit at depth and are sensitive to cold. Pigment-producing cells are among the most sensitive, which is why a pale mark can persist afterwards, and why the question is more consequential in darker skin. Nerves near the surface in some sites are another consideration, as are structures close to the surface at the edges of nails.
This is why repeat applications are common. A cautious first treatment that needs repeating is a better outcome than an over-enthusiastic one, and repetition is part of how the technique is used rather than evidence of failure.
What is the appointment like?
Brief, and the treatment itself is usually over in less time than the explanation takes.
A very cold substance is applied to the area, either sprayed or held against the skin with a probe. The sensation is a sharp sting during application and for a period afterwards. Anaesthetic is not usually used, partly because the procedure is so short.
The area whitens as it freezes and then thaws, and the whole cycle may be repeated within the same appointment. Afterwards the skin reddens, often swells, and a blister frequently forms over the following day, because the freezing separates the epidermis from the dermis and fluid gathers in the gap. That blister is expected.
Healing then takes a period that depends on the site, with the lower leg notably slower than the face. Aftercare instructions come from the clinic and are specific to the site and to what was treated.
Why is what something is established first?
Because destroying tissue destroys the opportunity to examine it.
Where a clinician is confident about what they are looking at, treating directly is reasonable. Where there is a question, that question is settled before anything is destroyed, since a sample cannot be taken afterwards from tissue that no longer exists.
This ordering occasionally surprises people who expected something to be dealt with on the day and find that a sample is proposed instead. It is a sequence rather than a delay.
What is worth asking?
Ask what is being treated and how confident the clinician is about it, particularly if nothing has been sampled before freezing.
Enquire about the mark to expect and whether a pale patch is likely, especially on a visible area and especially if your skin is darker. This is far better discussed before freezing than after it.
Ask how many rounds of freezing are anticipated, since knowing that repetition is normal changes how the second appointment feels.
Ask what healing looks like at your site and when it would be worth making contact. Lower legs in particular heal slowly, and knowing the expected course prevents unnecessary worry.
What this page does not do
It states no temperatures, no durations, no number of cycles and no aftercare routine, and it does not say what should be treated by freezing. That judgement belongs to a clinician who has examined the area.
Common questions
Does freezing hurt?
It stings during application and for a period afterwards, and most people describe it as sharp rather than severe. No anaesthetic is usually used, partly because the procedure is brief. The area is commonly sore for some time after the appointment.
Why does a blister form afterwards?
Because freezing separates the epidermis from the dermis beneath, and fluid collects in the space. It is an expected consequence of the treatment working rather than a complication, and the clinic will explain what to do about it.
Why might treatment be repeated?
Because judging depth is genuinely difficult and a cautious first application may not have reached far enough. Repeating is a normal part of how this treatment is used rather than a sign that something failed the first time.
Can freezing change skin colour?
Pigment-producing cells are sensitive to cold, so a pale mark can remain where an area has been treated, and this is more noticeable in darker skin. It is worth raising before treatment on a visible area, because it may influence the decision.
Why would a clinician take a sample instead of freezing something?
Because freezing destroys tissue, and destroyed tissue cannot be examined. Where there is any question about what something is, establishing that comes first, since the opportunity to examine it does not survive the treatment.
Sources
- Patient information on skin conditions and treatments — British Association of Dermatologists (United Kingdom) · accessed
- Guidance — National Institute for Health and Care Excellence (England) · accessed
Last updated . How this page was written.