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Are TENS units safe? Benefits and contraindications of TENS therapy

TENS units have become popular as an alternative treatment for pain management. And because they are mostly safe, TENS units are available over the counter (OTC) and can be purchased online, without a prescription. There are however a few cases where TENS device should be avoided.

Understanding how TENS units work:

A Transcutaneous Electrical Nerve Stimulation unit (TENS) is a small battery operated device that has electrodes with adhesive pads that stick to the patient’s skin. These electrodes send small electrical impulses through the skin, into the nervous system, which reduces its ability to transmit pain signals to the spinal cord and brain. During the treatment, the patient only feels a tingling sensation in the area where the pads are being applied.

TENS units have a lot of benefits: they are a drug-free treatment and have minimal side effects and contraindications. TENS units are used by many health professionals to help relieve pain symptoms. For example, they are used in conditions such as back pain, bursitis, arthritis, tendonitis, post surgery pain, sports injuries, headache…etc. A TENS device is also very portable, and relatively discrete.

Do TENS units have any possible side effects?

Most users don’t experience any side effects after using a TENS unit. But this doesn’t mean that there aren’t any possible minor side effects. Some people may feel uncomfortable because of the tingling sensation the TENS device creates, and some also can feel little electrical shocks.

The adhesive pads used to attach the electrodes to the skin can also trigger an allergic reaction in some people, which may cause redness and skin irritation. And in this case, patients should use hypoallergenic pads.

What are the contraindications of TENS units?

Although TENS units are generally safe, there are a few cases where TENS devices and any other electrical stimulation device should be avoided.

  • Interference with other critically important medical devices: People with pacemakers, infusion pumps, defibrillators or any other similar devices should consult their physician before using a TENS unit. The electrical current generated by the TENS unit can interfere with the device.  For people with pacemakers, studies have shown that TENS units rarely interfere with bipolar pacing, but can inhibit unipolar pacing in some cases.
  • Pregnancy: TENS units are sometimes used as a non invasive method to alleviate labor pain. Although no side effects from the use of TENS during pregnancy have been reported, It is recommended that pregnant women do not use TENS units early in pregnancy, especially prior to the third trimester. This is because the effects of TENS on the fetus are unknown. Pregnant women should also avoid using TENS in the abdominal and pelvic regions.
  • Use on the head and neck: using TENS units on the head and neck is not recommended. And for patients with epilepsy, applying electrodes to the head or neck may trigger seizures. People with blood or blood vessel disorders should also avoid placing the TENS electrodes on the head or neck.

TENS therapy is not a cure:

Probably the biggest risk related to TENS units is the fact that it only treats the symptoms of pain, and does not eliminate the cause. Before using a TENS unit, you should always see a physician to determine the underlying causes of the pain.

Are TENS units FDA approved?

Electrical stimulators are considered devices under the Federal Food, Drug, and Cosmetic Act. Under this law and the agency’s regulations, the FDA is responsible for regulating the sale of all electrical stimulators in the United States.  A lot of the TENS units that are available over the counter have already received FDA approval, but it’s not rare to find devices that haven’t received FDA premarket requirements online.  In order to check if a device has received FDA clearance, you can ask the seller about the 510K number and check the FDA’s website here: