TENS is generally reported as well tolerated. Skin irritation and redness are the most common adverse reactions (90;47;120;138;189;211), occurring in up to one-third of patients (212;213). Hives, welts, or contact dermatitis/allergic skin reactions may occur with the use of electrodes and electrode paste {Cauthen JC, 1975 1325 /id;Marren, 1991 1177 /id;Al'Ajlan, 2000 1178 /id;Dwyer, 1994 1179 /id;Meuleman, 1996 1181 /id;Castelain, 1986 1760 /id;Zugerman, 1982 314 /id;Meyler WJ, 1990 230 /id}. Electrical burns may occur with excess use or improper technique (221). Due to the risk of burns, TENS should be used cautiously in people with decreased sensation, such as with neuropathy.

TENS should not be used in patients with implantable devices such as defibrillators, pacemakers, intravenous infusion pumps, or hepatic artery infusion pumps (222). Electrical shocks or device malfunction may occur.

There are isolated case reports of lung atelectasis and edema, paresthesias, pain, and increased hair growth with the use of TENS. Seizures have been reported, and TENS should be used cautiously in people with seizure disorder (223;224). Unpleasant sensations at and away from the site of TENS, headache, muscle aches, nausea, agitation, and dizziness have also been reported (77). It is also sometimes suggested that TENS may affect the cardiovascular system, increasing heart rate and reducing blood pressure (17).

TENS cannot be recommended during pregnancy due to insufficient evidence, and due to a theoretical risk of harm to the fetus. Fetal heart rate may be elevated (225). Although multiple trials of TENS for pain relief during childbirth have been published, interference with fetal heart monitoring equipment may occur (105), and this technique should not be used unless under the strict supervision of an experienced licensed healthcare practitioner. Safety of TENS is not established in children.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Dental procedures (Grade: B)
Several small randomized controlled trials in adults (

Knee osteoarthritis (Grade: B)
Multiple randomized controlled trials have examined the effects of TENS in patients with osteoarthritis of the knee (

Anesthesia (pain relief during surgery) (Grade: C)
Auricular TENS is sometimes used in Europe to reduce the need for anesthesia during surgical procedures. There is not enough reliable evidence to draw a firm conclusion in this area (

Alzheimer's disease (Grade: C)
Preliminary research suggests that TENS may benefit some symptoms of Alzheimer's disease, including mood, memory, and cycles of daily rest and activity (

Angina (chest pain) (Grade: C)
Several small, brief studies report benefits of TENS on angina pectoris pain (

Ankylosing spondylitis (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Back pain (Grade: C)
The effects of TENS or acupuncture-like TENS on low back pain remain controversial, and multiple controlled trials have been published in this area (

Burn pain (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Cancer pain (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Chronic pain (Grade: C)
The effect of TENS on chronic pain of various causes and locations remains controversial, and multiple controlled trials have been published in this area (

Dysmenorrhea (painful menstruation) (Grade: C)
TENS has been examined for the treatment of dysmenorrhea in several small studies (

Headache (Grade: C)
Preliminary controlled trials suggest that TENS may have some benefits in patients with migraine or chronic headache (

Hemiplegia / hemiparesis (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Labor pain (Grade: C)
The effect of TENS on labor pain remains controversial, and multiple controlled trials have been published in this area (

Local anesthesia during gallstone lithotripsy (Grade: C)
TENS has been tested for its effects on pain control during lithotripsy (a technique used to break up gallstones). Currently, there is not enough reliable evidence to draw a firm conclusion in this area (

Facial pain / trigeminal neuralgia (Grade: C)
Several studies report benefits of TENS in patients with chronic facial pain of various causes (

Myofascial pain (Grade: C)
There is preliminary data that high frequency/high intensity TENS may benefit myofascial pain. However, currently there is insufficient evidence from well-designed controlled trials to support this use.

Nausea/vomiting of pregnancy (Grade: )
There is not enough reliable evidence to draw a firm conclusion in this area (

Neck and shoulder pain (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Pain from broken bones / acute trauma (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Peripheral neuropathy (Grade: C)
Several case reports and a small number of controlled trials (

Phantom limb pain (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (

Post-herpetic neuralgia (Grade: C)
TENS has been used in post-herpetic neuralgia, however there is insufficient evidence from controlled clinical trials upon which to base recommendations (

Post-operative ileus (Grade: C)
There is conflicting evidence from clinical trials on the effectiveness of TENS in post-operative ileus (

Post-operative nausea / vomiting (Grade: C)
There is not enough reliable scientific evidence to firmly conclude if TENS is beneficial in patients with pain after surgery (

Post-operative pain (Grade: C)
There are multiple controlled studies of TENS for pain following various types of surgery, including abdominal surgery (

Post-stroke rehabilitation (Grade: C)
Studies of TENS in post-stroke rehabilitation report inconsistent findings, and benefits have not consistently been demonstrated (

Rheumatoid arthritis (Grade: C)
Preliminary studies of TENS in rheumatoid arthritis report improvements in joint function and pain (

Skin flap ischemia (Grade: C)
TENS has been tested for its effects on blood flow to skin flaps used in plastic surgery procedures such as breast reconstruction. Currently, there is not enough reliable evidence to draw a firm conclusion in this area (

Skin ulcer (Grade: C)
TENS has been evaluated in patients with diabetic foot ulcers and chronic ulcers of other causes (

Spinal cord injury (Grade: C)
There have been limited non-controlled trials of TENS in spinal cord injury. Well-designed controlled trials are required to recommend for or against the use of TENS for this indication.

Temporomandibular joint pain (TMJ) (Grade: C)
There is insufficient reliable evidence to recommend for or against the use of TENS in temporomandibular joint pain (

Urinary incontinence / detrusor instability (Grade: C)
There is not enough reliable evidence to draw a firm conclusion in this area (