Cryotherapy - guideline for professionals performing cryotherapy (G061)

This guideline provides recommendations and good practice points regarding the use of cryotherapy which is the name given to treatments which involve liquid nitrogen spray freezing the skin and tissues, resulting in cytolysis (cell breakdown) at the dermal junction and subsequent necrosis¹. Liquid nitrogen is a hazardous substance which requires great care during handling².

Only healthcare professionals who have received appropriate training may administer cryotherapy.

Health Care Assistants, although not involved with performing cryotherapy, may decant liquid nitrogen only if they have received appropriate information and training and been made aware of the risk assessment and also the Control of Substances Hazardous to Health (COSHH) Assessment. All staff who decant liquid nitrogen and perform cryotherapy treatment should be aware of the potential hazards associated with liquid nitrogen use.

Emergency procedures, storage, handling and use of liquid nitrogen are in appendix 1.

Cryotherapy results in a localised area of frostbite which is thought to stimulate the body’s immune response to combat the virus that produces warts. To achieve maximum effect from cryotherapy a basic knowledge of the following is required:

• knowledge of the relevant skin lesions that can be treated with cryotherapy
• what to expect from cryotherapy treatment
• how to administer cryotherapy treatment
• how often to administer cryotherapy.

• to treat minor skin lesions such as viral warts, skin tags and solar keratoses by stimulating immune response process in patients
• to minimise the use of wart paints and creams.

Lesions which can be treated with cryotherapy are:

• viral warts
• solar keratoses
• Bowens disease
• skin tags
• seborrhoeic keratoses
• Molluscum contagiosum

It is at the discretion of the individual practitioner to assess the suitability of the client to receive cryotherapy.

This section references West of Scotland Managed Clinical Network (2024). External anogenital warts. 

• Cryotherapy is the treatment of choice for a small number of keratinised lesions, intrameatal warts and in pregnancy.
• Treatment should be applied until a halo of freezing has been established a few millimetres round the treated lesion. A freeze, thaw, freeze technique should be used.
• Response rates depend on size and chronicity of the lesions.

The skin and surrounding tissue which has been treated with liquid nitrogen can sting a little and after treatment the area may blister and become painful. This is a normal response to cryotherapy treatment and the patient should be advised to keep the area clean and dry. The lesion should fall off with the roof of the blister and should leave a healthy skin underneath. Just like any other blister if it becomes broken it can result in localised infection, this is very unusual but the patient should be advised to seek medical advice if this does occur.

Care of the treated site

• Keep the treated area clean and dry.
• Only apply a dressing if area becomes red, painful or weeps fluid – if necessary seek medical or nursing advice.
• For genital warts, salt baths may provide relief.
• Paracetamol can be taken for pain relief

Employees are reminded that they may have patients/carers who require communication in an alternative format e.g. other languages or signing. Additionally, some patients/carers may have difficulties with written material. At all times, communication and material should be in the patient’s/carers preferred format. This may also apply to patients with learning difficulties.

In some circumstances there may be religious and/or cultural issues which may impact on clinical guidelines e.g. choice of gender of health care professional. Consideration should be given to these issues when treating / examining patients.

Some patients may have physical disability or impairment that makes it difficult for them to be treated / examined as set out for a particular procedure requiring adaptations to be made.

Patients’ sexual orientation may or may not be relevant to the implementation of this guideline, however, non-sexuality specific language should be used when asking patients about their sexual history. Where sexuality may be relevant, tailored advice and information may be given.

This guideline has been impact assessed using the NHS Ayrshire and Arran Equality and Diversity Impact Assessment Toolkit.

1. United Kingdom National Guideline on the management of anogenital warts (2015). British Association of Sexual Health and HIV [online]. Available from www.bashh.org/guidelines.
2. West of Scotland Managed Clinical Network (2024) External anogenital warts.
   Available from: https://www.wossexualhealthmcn.scot.nhs.uk/wp-content/uploads/2024/07/West-of-Scotland-Warts-External-Anogenital-V.7.1-May-24-1.pdf
3. BOC (2005) Care with Cryogenics. Available from: Official BOC Gases | Gas, equipment & accessories | Services & industries - UK

Storage

• Liquid nitrogen should be stored in a suitable container fitted with an appropriate withdrawal device. Withdrawal devices must only be fitted to Dewars for which they are designed.
• Liquid nitrogen containers whether full or part-full should be stored in a well ventilated dry area. The Dewar ‘dust caps’ must always be fitted whilst in storage. Handle empty Dewars in the same manner as you would handle full Dewars as they will still have some residual content.
• The liquid nitrogen should be stored in the designated container, in a locked store cupboard that is ventilated and has the appropriate signage, and only transferred into the cryotherapy flask prior to the start of the clinic. Any surplus liquid nitrogen should not be transferred back into the container but allowed to evaporate, in a well ventilated room. Managers should ensure that when leaving any flask to evaporate that all staff groups are considered and informed of the risks, i.e. domestics who may have to go into the room to clean out of hours.
• There may be a need to fit oxygen depletion monitors in the room where the liquid nitrogen flask is held, this would be identified in the risk assessment and based on quantity stored, room size, ventilation and building usage.
• All departments using liquid nitrogen should have completed a Health and Safety Risk assessment and also a COSHH Risk assessment form. These are available to download on AthenA: http://athena/ohrd/ohs/assform/Generic%20Risk%20Assessments/HS-Generic-006.docx  and can be found under H&S manuals. The Occupational Health and Safety Department have produced generic risk assessments and safe systems of work as the minimum standard that should be in place.

Transport

• Transportation of liquid nitrogen, no matter how small the quantity, should only be undertaken by trained personnel who are aware of the potential hazards and emergency procedures. Transportation must be in an approved vehicle type. Guidance on vehicle transportation can be obtained from the Dangerous Goods Safety Advisor. Under no condition should Dewars containers be transported in a private car, taxi, van.
• Minimise the number of stairways/doorways which require to be negotiated.

Handling and use

• Decanting of liquid nitrogen to be undertaken by personnel trained in this procedure only. Procedure must be performed in a well ventilated room. Liquid should be poured slowly, pausing mid-way to allow liquid to settle which will help minimise risk of thermal shock. Keep vessel upright at all times, except when pouring liquid from Dewars specifically designed for that purpose.
• Goggles (preferably a visor) to fully protect eyes and full length plastic aprons should be worn over uniform or personal clothing.
• Protective gloves should be worn. Gloves should be loose fitting (for easy removal) thermal insulated and should have a ribbed cuff to protect the wrist area and prevent any spillage of liquid nitrogen from contacting the skin.
• Be careful to avoid spillage during handling. This could lead to cold burns or oxygen depletion.
• Metallic jewellery should be removed.
• Feet should be adequately covered. Open toed shoes should not be worn.
• Decanting of substance in to smaller container should be done by trained personnel only. In the event of a faulty Dewar, no attempt should be made to repair this locally. All repairs must be completed by the manufacturer or competent supplier.
• Equipment should be inspected regularly at every refill of liquid nitrogen. Staff should not use equipment if visually it appears faulty. Any suspected faults should be reported to the Laboratory Manager at Crosshouse Hospital.
• Exposed skin should be kept to a minimum. Legs and arms should be covered.

Disposal

• Any liquid nitrogen remaining in the small flask, should not be transferred back into the container but allowed to evaporate, in a well ventilated room.
• Liquid nitrogen will be uplifted for disposal by designated Board staff – contact Biochemistry, Crosshouse Hospital, 01563 521133 Extension 27403.

Spillage/emergency procedures

In the event of spillage:

• Evacuate area immediately.
• A representative from Health and Safety should be informed of the incident immediately.
• Do not allow anyone to enter the area until you are sure that the nitrogen gas has all dispersed and that the air is safe to breathe. If in doubt, use an oxygen monitor to check oxygen levels.
• Report incident by completing Datix electronically.

In the event of inhalation:

• Persons suffering from lack of oxygen should be moved to fresh air.
• First aid should be given if required.
• If breathing is difficult, administer oxygen if available, keep person warm and send for ambulance without delay – dial 999.
• If casualty is not breathing, commence artificial respiration.
• Do not enter area where there is suspected oxygen deficiency even for purposes of rescue.

For spillage on skin:

• Flush area of skin with tepid water.
• Do not use a forceful flow of water as this may cause tissue damage.
• Do not use direct heat or hot water.
• Remove any clothing that may restrict circulation to affected area.
• Any clothing adhering to the affected site should not be removed until affected area has thawed, otherwise tearing of flesh may occur (thawing may take 15-20 mins)
• Move casualty to warm area and call ambulance.
• Affected area when thawed should be placed in warm water.
• Apply sterile dressing to affected area when thawed to help protect against infection and swelling.
• Inhalation of cold vapour may trigger asthmatic attack.

Eye contact:

• Flush eyes thoroughly with tepid water for at least 15 minutes.
• Do not use hot water.