Transcutaneous electrical nerve stimulation (TENS) Dr Trisha Macnair This method of pain relief is popular across the world, but some experts in the UK are sceptical about its use.

Pain relief

The management of pain by UK doctors is improving but there still isn’t nationwide access to specialist pain clinics and those that do exist often have lengthy waiting lists.

TENS is widely used around the world for a variety of painful conditions (for example, there are an estimated 450,000 users annually in Canadian state hospitals, while in Scandinavia TENS is well known as a treatment for period pain). In the UK, the use of TENS is increasing in many fields and, whilst originally used by women in labour, it‘s now marketed for most sorts of pain, especially musculo-skeletal.

How does it work?

A small electrical device delivers electrical impulses across the skin. The device is usually about the size of a personal stereo, although lightweight versions not much bigger than a credit card are available.

The device is connected by wires to sticky pad electrodes, which are placed on the skin in the area of the pain. This allows a small, low-intensity electric charge to be passed across the area.

TENS is thought to work in two ways:

• On a high frequency, by selectively stimulating certain 'non-pain' nerve fibres to send signals to the brain that block other nerve signals carrying pain messages.
• On low frequencies, by stimulating the production of endorphins, natural pain-relieving hormones.

The device is usually used for 15 to 20 minutes, several times a day, and is controlled by the user rather than a health professional. Pain relief may be rapid and last for days.

Unlike many pain-relieving drugs, TENS isn't addictive and seems to have few side-effects. Most people can use a TENS machine but it’s not suitable for:

• Epileptics.
• Those with pacemakers and certain other types of heart disease.
• Unknown causes of pain.
• Unsupervised in pregnancy (other than in labour).

Claims and counter-claims

Some of the claims made for TENS could lead you to think it's the miracle cure for pain. Back pain, arthritis, migraine, sports injuries, period pains and even non-painful conditions such as sleeplessness and stress are said to improve with its use.

But while TENS is widely recommended in the UK as a way of controlling labour pain, a review by the Pain Research Unit at Oxford University, published in 1997, found that evidence for it having an analgesic effect in such circumstances was weak. The unit could find no study of note showing any difference in pain intensity or pain relief scores between TENS and a placebo treatment during labour. There has not been any substantial study since, supporting its use.

TENS has also been recommended for treating pain following surgery but, according to the UK College of Anaesthetists, it isn't effective on its own as pain relief for acute moderate to severe postoperative pain.

There's also some controversy as to whether TENS is effective for chronic pain, and some experts feel that more research needs to be done in this area.

Pain is highly individual and you may feel that it's worth trying TENS. In addition, while it may not bring guaranteed pain relief on its own, TENS may be effective when used in combination with other pain treatments.

Talk to your doctor first and find out where you can hire a machine from before buying one yourself. Try your local health centre, high street chemist, hospital pain clinic or branch of the National Childbirth Trust.

This article was last medically reviewed by Dr Gill Jenkins in June 2009.