A transcutaneous electrical nerve stimulation (TENS) unit is a battery-operated device that some people use to treat pain.
TENS units work by delivering small electrical impulses through electrodes that have adhesive pads to attach them to a person's skin.
These electrical impulses flood the nervous system, reducing its ability to transmit pain signals to the spinal cord and brain.
The same electrical impulses also stimulate the body to produce natural pain relievers called endorphins.
In this article, learn more about the uses of a TENS machine and the research on its effectiveness.
TENS units may help treat the following symptoms:
They may also alleviate pain that results from the following conditions:
- sports injuries
- multiple sclerosis
- painful diabetic neuropathy
- spinal cord injury
A TENS unit has controls that allow people to administer an appropriate level of pain relief. People can achieve this by altering the following aspects of the electrical current:
Intensity: A dial allows the user to adjust the intensity of the electrical stimulation.
Frequency: The frequency refers to the number of electrical pulses per second. High-frequency (HF) pulses range from 80 to 120 cycles per second and may help manage acute pain. Low-frequency (LF) pulses range from 1 to 20 cycles per second and are suitable for the treatment of chronic pain.
Duration: The duration is the number of microseconds that the current enters the skin for during each pulse.
TENS is a noninvasive method for relieving pain. People who experience pain relief from TENS may be able to reduce their intake of pain medications, some of which can be addictive or cause adverse side effects.
TENS units are also convenient because they are small, portable, and relatively discrete. People can carry a TENS unit in their pocket or clip it onto a belt to ensure that they have immediate access to pain relief throughout the day.
It is safe for most people to use a TENS unit, and they will not usually experience any side effects.
However, the electrical impulses that a TENS unit produces may cause a buzzing, tingling, or prickling sensation, which some people may find uncomfortable.
Some people may be allergic to the adhesive pads. Anyone who experiences skin redness and irritation can switch to using hypoallergenic ones instead.
It is vital never to place the electrodes on either the front of the neck or the eyes. Putting electrodes on the neck can lower blood pressure and cause spasms. On the eyes, the electrodes can increase pressure within the eye and possibly cause an injury.
Although it is safe for most people, experts recommend that some groups of people avoid TENS treatment unless a doctor advises its use.
This recommendation applies to the following people:
- Pregnant women: Pregnant women should avoid using TENS in the abdominal and pelvic regions.
- People with epilepsy: Applying electrodes to the head or neck of people with epilepsy may induce seizures.
- People with heart problems.
- People with a pacemaker or another type of electrical or metal implant.
Due to a lack of high-quality research and clinical trials, researchers have not yet determined whether TENS is a reliable treatment for pain relief.
While there is a lack of strong clinical evidence for its effectiveness, TENS is a low-risk pain relief option for many people.
Several factors may influence the effectiveness of TENS:
Research shows that people who use a TENS unit on a daily basis at the same frequency and intensity can develop a tolerance to the treatment.
A person who develops tolerance will no longer feel the same level of pain relief that they did when they first used the unit.
To prevent this from occurring, people can alternate between LF and HF TENS within each treatment session.
Alternatively, they can gradually increase the intensity or duration of TENS on a daily basis.
The range of intensities of the electrical stimulation may account for some of the differences in research findings.
According to a 2014 review, HF TENS treats pain more effectively than LF TENS. In fact, many studies have found LF TENS to be ineffective.
Given that HF TENS is a more effective pain reliever, experts recommend that people apply the highest-intensity TENS that they can tolerate.
TENS may be more effective if people place the electrodes on acupuncture points.
Acupuncture is a practice that uses needles to stimulate the nerves beneath the skin at specific locations known as acupuncture points. Experts believe that this assists the body in producing endorphins.
One review found some evidence that people who receive TENS through acupuncture points may experience a reduction in pain.
The duration of pain relief after using a TENS unit can vary. Some people report that their pain returns as soon as they switch off the device. Others continue to experience an adequate level of pain relief for up to 24 hours.
A 2012 review suggests that the duration of pain relief increases after repeated TENS treatments. However, this repetition can also increase the likelihood of a person building up a tolerance to the treatment.
The research on using a TENS unit for pain relief has so far yielded inconsistent results due to a lack of high-quality scientific studies and clinical trials.
Some research suggests that TENS treatment can relieve pain, but this may be dependent on certain factors, such as the affected area of the body and the treatment intensity. Knowing how these factors affect TENS can help people use it more effectively.
Most people can use a TENS unit safely, and few will experience side effects. However, it is best to speak to a doctor before trying TENS either as an alternative treatment or in combination with other methods of pain management.
TENS units are available to purchase at some pharmacies and online.