TENS devices can affect the operation of demand type cardiac pacemakers.

TENS is not recommended for patients with known heart disease without first consulting their doctor.  

Do not stimulate over the eyes or carotid sinus nerves.

Do not apply TENS for undiagnosed pain syndromes until etiology is established.

Do not apply TENS if you suffer from epilepsy.

         As with all medical devices, if in any doubt consult your doctor before using.