Transcutaneous Electrical Nerve Stimulation (TENS) is a non-invasive method of pain management that delivers mild electrical impulses through electrodes placed on the skin. A TENS unit provides symptomatic pain relief by interfering with pain signals traveling to the brain and promoting the release of the body’s natural pain-relieving chemicals. While TENS is widely considered safe for most users when guidelines are followed, it requires strict adherence to usage and placement protocols to prevent adverse effects. Understanding the potential risks and necessary safety precautions is important for anyone considering this therapy.
Minor Adverse Effects
The most common side effects associated with TENS therapy are generally mild, localized, and temporary, often stemming from the interaction between the electrodes and the skin. Skin irritation, known as contact dermatitis, is frequently reported and can manifest as redness, itching, or a mild rash where the adhesive pads are applied. This irritation can be caused by the adhesive itself, particularly for individuals with sensitivities, or by poor skin preparation.
Users may also experience an uncomfortable prickling or tingling sensation if the intensity setting is too high, or mild muscle soreness following a session. Excessive electrical intensity can cause underlying muscles to twitch, potentially leading to muscle fatigue or temporary soreness. Switching to hypoallergenic adhesive pads or ensuring the skin is clean and dry before use can typically resolve most issues related to skin irritation.
Absolute Contraindications
The danger associated with TENS units arises when the electrical current interferes with biological systems or implanted medical devices.
Implanted Devices and Sensitive Areas
The use of a TENS unit is strictly forbidden for individuals who have implanted electronic devices, such as a cardiac pacemaker or an implantable cardioverter-defibrillator (ICD). The electrical impulses from the TENS unit can interfere with the function of these life-sustaining devices, potentially leading to device malfunction or an erratic heart rhythm.
TENS should never be used over the front of the neck, specifically over the carotid sinus area. Stimulation in this region can cause a sudden, dangerous drop in blood pressure and heart rate due to the activation of baroreceptors, and it may also trigger laryngeal spasms. Similarly, placement over the eyes is forbidden due to the potentially harmful effects of electrical current on the ocular structures.
Pregnancy and Disease
For pregnant individuals, TENS use, especially over the abdomen, pelvis, or lower back, is an absolute contraindication because the safety and effects on the developing fetus have not been established through research. The electrical current may also pose a risk of inducing premature labor if applied near the uterus.
Electrodes should not be placed directly over areas affected by active malignancy (cancer) or active infection. While TENS may be used for pain management in palliative care, placement directly over a known cancerous lesion is avoided due to the theoretical risk of altering cell behavior or metastasis. The current should also be avoided on skin that is broken, damaged, or severely irritated, as this increases the risk of skin burns or further irritation. TENS should not be used transcranially, or through the head, unless specifically directed by a healthcare professional, as the effects on the brain are not fully understood.
Ensuring Safe Operation
Safe and effective TENS therapy requires careful attention to device quality, placement, and intensity settings. Use only FDA-cleared devices that meet established safety standards. Before each use, the TENS unit must be turned off before attaching or detaching the electrode pads to prevent unexpected shocks.
Correct electrode placement is critical to prevent discomfort and potential harm. Pads should be placed around the perimeter of the painful area, avoiding bony prominences, which can cause discomfort. Ensure they are spaced far enough apart to prevent the current from jumping between them. The skin underneath the electrodes must be clean and dry to ensure proper adhesion and conductivity, minimizing the risk of irritation or electrical burns.
Users must approach intensity settings with caution, starting at the lowest level and increasing gradually until a strong, comfortable tingling or buzzing sensation is felt. The intensity should never be increased to a level that causes pain or excessive muscle contractions. Prolonged, continuous use can lead to skin damage or muscle fatigue, so users should take breaks between sessions.
If pain symptoms worsen, or if the user experiences unusual symptoms like dizziness, nausea, or persistent skin reactions, they should immediately discontinue use. Consulting a healthcare provider is necessary to determine the appropriate settings, placement, and duration of therapy.