Therapeutically, electromotive drug administration(EMDA) delivers a medicine or other chemical through the skin. It is an injection without a needle, and may be described as non-invasive. It is different from dermal patches, which do not rely on an electric field. It drives a charged substance, usually a medication or bioactive agent, transdermally by repulsive electromotive force, through the skin. A small electric current is applied to an iontophoretic chamber placed on the skin, containing a charged active agent and its solvent vehicle. Another chamber or a skin electrode carries the return current. One or two chambers are filled with a solution containing an active ingredient and its solvent vehicle. The positively charged chamber, called the anode, will repel a positively charged chemical species, whereas the negatively charged chamber, called the cathode, will repel a negatively charged species into the skin. Common diagnoses treated with iontophoresis include plantar fascittis, bursitis, lateral and medial epicondylitis (commonly referred to as tennis elbow and golfers elbow respectively) and some types of palmar-plantar hyperhydrosis.