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What is Entonox?

Entonox is a gas made up of 50 percent nitrous oxide and 50 percent oxygen. It is also referred to as ‘laughing gas’ or ‘gas and air’ and is commonly used in childbirth.

When is it used?

Entonox can be used to reduce the pain and anxiety created by short, painful procedures whilst receiving treatment in hospital.

How will I receive the gas?

The gas is self-administered via a cylinder with tubing and a mask or a mouthpiece attached to it. The mask is clear and to make it more child friendly, smells of a variety of flavours such as cherry, strawberry and bubble-gum.

How long does it take to work?

When breathed in efficiently the gas should be working after about 1 minute, however there will be several minutes to keep breathing the gas in before a procedure is commenced. You will need to continue breathing in the gas throughout the procedure for it to remain effective.

Who will supervise me?

Supervision will be provided at all times by a qualified nurse, trained to supervise the self-administration of Entonox. You will be shown how to use Entonox and will be asked to hold the mask over your own nose and mouth. If you are using a mouthpiece you will have to mouth breath only. The gas is self-administered at all times. When you feel that you have had enough gas, you will be free to take the mask or mouthpiece away at any time.

Can I receive other painkillers too?

Yes, you will still be able to receive other pain relief as normal, should it be required.

What are the side effects?


Nausea is a side effect that happens not very often. Because of this, we would recommend, where possible, that you have not eaten up to an hour prior to the procedure. However this is not essential and eating will not exclude you from this facility.

Tingling sensation

Occasionally children report a tingling sensation around their lips and at the tips of their fingers and toes. This is harmless and will disappear on stopping breathing the gas.

You should remain awake and co-operative throughout the procedure.

How long will it take to recover?

The gas is very short acting. It will take 2 to 3 minutes to get out of your system. However, some children feel a little light headed for several minutes afterwards, so you will be given as much time as necessary to recover.

Is there a time when Entonox will not be used?

Yes. It will not be used in the following circumstances:

  • A child who is not able to understand and co-operate.
  • A child who has a decreased level of consciousness such as a recent head injury, intoxication or coma.
  • A child who has air trapped within the body and where expansion may be dangerous.
  • In patients who have vitamin B deficiency or have a disorder of vitamin B12 metabolism.
  • Within the first trimester of pregnancy.

If you are pregnant, we need to know, as you must not be in the area where Entonox is used.

Contact us

If you have any questions or concerns about Entonox please speak with the pain team.

You can contact the pain nurses between 8.30am and 5.30pm from Monday to Friday on telephone number 0114 271 7397. If it is out of hours please leave a message and we will get back to you.

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Contact us


Please note this is a generic information sheet relating to care at Sheffield Children’s. The details in this resource may not necessarily reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If you have specific questions about how this resource relates to your child, please ask your doctor.

Resource number: PAI4

Resource Type: Article

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United Kingdom

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