Are there side effects when using a TENS unit?

When used correctly, there are no TENS machine side effects to speak of. However, some adverse effects may crop up here and there, but they’re nothing that can’t be fixed by being a little bit more careful. For instance, prolonged application in a single area may lead to skin irritation. Most TENS units include a gel that improves conductivity and may keep the skin from becoming irritated. The only problem would be that the person turned out to be allergic to that gel, but that only happens in very rare occasions. 
Extended use of this technology may also lead to muscle twitching. Generally speaking, these devices are actually designed to be used for as long and as often as it is necessary to enjoy pain relief. Users are encouraged to take advantage of that as long as they remain comfortable. They are also advised to try different settings to find out what works for them.  If TENS doesn’t seem to be taking effect, it may be because the intensity chosen is too low. On the other hand, if the user experiences discomfort, it may be because the intensity is too high.  What works for one person may not work for others, and vice-versa. 

Further TENS machine side effects may be brought about by misplacement of the electrodes. Electrode pads are not meant to be placed over the front and sides of the neck, the temples or across the head, over or near the eyes, or on open wounds and broken skin. People with pacemakers or heart disease should used this technology with extreme care, and only if their doctors allow them to. This is because TENS may cause irregular heart rhythms. In fact, people should consult a physician before and while using a TENS machine, and follow instructions, both their doctor’s and the accompanying manual’s.
Using a TENS unit as it is intended too will not only maximize pain relief but also decrease possible side effects, which are already minimal as it is. These lack of major side effects is what makes TENS technology such a sought-after treatment for pain. Analgesics usually are laden with side effects, which are sometimes even worse than the pain itself. While TENS may not work for everybody, it certainly doesn’t hurt to try; on the contrary, chances are that you will hurt less after undergoing TENS pain management therapy.   

Related Read: What is a TENS Unit?