In a nutshell, basic problems encountered by pain patients whose electrodes won't stick are:
(1) skin debris on re-usable self-adhering electrodes,
(2) dried out adhesive, and
(3) too much water (over saturation) of adhesive.
Additionally, the skin should be cleaned with soap and water. Never use alcohol, lotions, oils, or creams on the skin prior to placing the electrodes. Pre- and post-treatment skin care products are protect the skin and help to keep the treatment area healthy. Read on and/or watch tens electrode care video.
Reusable electrodes need to be clean to stick and to be effective. Always check the electrode gel for tac ( stickiness) prior to using the electrode. If the gel does not readily adhere to a gentle touch of your fingertip then the skin residue (dead skin cells, salts, oils from your skin) is on the surface and needs to be cleaned. Clean the electrode gel gently with a moist cloth (not a paper towel or tissue or anything that will stick to the gel). Wipe the surface area whisking away the particle matter. If the surface is flat you may want to take an old toothbrush and stroke the surface gently in one direction. This actually fluffs up the surface area and gives more stickiness to the electrode.
Reusable self-adhering electrodes need to be hydrated. If you have cleaned the electrode, but still do not feel the tac of the gel, rub only a drop of water on the gel surface and repeat until the surface has been completely hydrated. Do not hold the electrode under the faucet as this will cause too much water or "saturation".
Over saturation can occur if electrodes are worn too long at a time. The electrode will absorb and retain moisture from perspiration, hot/humid environments, or excessive addition of water to re-hydrate the gel surface. To extend the life of the electrodes, rotate their use. They should be rotated every 4 to 6 hours, especially if being used in a hot or humid environment. Over-saturation results in the eventual lessening of the physical and adhesive properties of the gel. The electrodes should be removed from the skin and allowed to air dry in a cool and dry environment, with the gel exposed to the air for at least 24 hours. The electrodes can be stored on their original plastic sheet in the refrigerator if you want. The refrigerator, being frost free, will remove any excess humidity.