Generally TENS units are considered to be safe, however you should always speak to your doctor or another medical professional before starting to use one.
The National Health Service (NHS) in the UK report that most people who use TENS do so without experiencing any side effects. However in a very rare number of cases burns and irritations of the skin have been reported.
There are also a number of groups that should avoid the therapy, such as those who have epilepsy or women in the early stages of pregnancy.
The NHS provides a list of those who should not use TENS treatment:
TENS is not safe for everyone to use. Do not use it without first getting medical advice if:
- You have a pacemaker or another type of electrical or metal implant in your body
- You’re pregnant, or there’s a chance you might be pregnant – TENS may not be recommended early in pregnancy
- You have epilepsy or a heart problem
In the past it was fairly common that a very small number of users would have an allergic skin reaction to the pads, approximately 2-3%.
To counter this, manufacturers moved to latex-free pads. Despite this, if you do have allergies then it’s essential that you still check the material of the electrodes before use.
Other side effects from a TENS machine are often down to people not following guidance correctly and overusing the tool or having the intensity set too high.
It’s essential to remember that you are using electrical nerve stimulation on your skin. Using it too much can make the treatment area sore.
Excessive intensity can also make your muscles twitch and result in unpleasant sensations.
The MidSouth Pain Treatment Center recommends a 30 minute limit:
TENS stimulation should last for only 30 minutes at a time. After this, a 20-minute break is advised to give your skin a break for potential skin irritation from using TENS in one area on the skin for too long.
It’s important to note that there are also a number of different places on your body that you shouldn’t place electrodes.
For example, it’s not recommended that TENS pads are placed on any part of your head, face or throat.
Medical professionals within University of Iowa Hospitals & Clinics, summarize exactly where a TENS unit should not be used:
Do not use TENS on:
- Open wounds or rashes
- Swollen, red, infected, or inflamed skin
- Cancerous lesions, or close to them
- Skin that does not have normal sensation (feeling)
- Any part of your head or face
- Any part of your throat
- Both sides of the chest or trunk at the same time
- Directly on your backbone
If you use the machine as advised by your physician and the manufacturer, it’s unlikely that you’ll experience any side effects.
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