Iontophoresis is a method of delivering a drug through the skin that involves electricity. Unlike a hypodermic, or powderject it is not an instentaneous process, an takes time to happen.

Many chemicals are charged, either positively, or negatively. As everyone knows, like charges repel. If a drug of a certain charge is put on the skin, and a similar charge placed above it, the only direction it can move is down. It may seem illogical that the skin could be penetrated, because we think of it as solid. However, this is happening on the molecular level, and so drug molecules can go through the top layer of skin, the stratum corneum. Once through their they can be absorbed, and have an effect.

Iontophoresis is only suitable for treatment of conditions that occur locally. The drug must be placed exacly where it is needed, as it does not enter the blood supply and circulate round the body. The most common conditions that can be treated with iontophoresis are localised skin disorders. It can also be used to deliver a limited local anaesthetic.

Some drugs can be delivered at a controlled rate by wearing a wristband that passes a current through the skin, causing gentle iontophoresis.