Iontophoresis is a technique that uses a weak DC current, applied to the part of the body to be treated, to carry drugs through intact skin. In hyperhidrosis, simple tap water iontophoresis is used, normally without adding any active substances, to treat patients who have not achieved satisfactory results with antiperspirants.
The mechanism of action is not fully understood, but it is thought that the electrical current produces a minimal thickening surface layer of the sweat ducts, so that the perspiration is reduced or even blocked. In addition, the sensitivity of the sweat receptors that respond to stimulation of the gland seem to become impaired.
The treatment consists in placing the hands and/or the feet in flat containers which are partially filled with water and have electrodes and cables connected to a DC generator. The intensity of the current is increased with a knob until a slight tingling sensation is felt. 
For the armpits and other parts of the body, there are special electrodes available(electrode pads of absorbent material) that have to be soaked in water before use.
Tap water seems to be an ideal conducting fluid, better even than saline for the purpose of inhibiting the sweat glands, despite saline being a better conductor. Only exceptionally, in areas with tap water of extremely low conductivity (almost no mineral content), half a teaspoon of bicarbonate can be added to 1 liter of water in order to improve conductivity.
Each treatment lasts around 15-30 minutes. In the beginning, it should be performed daily or every 2 days over a period of 1-2 weeks until the sweating stops. The duration of dryness varies from person to person and can last for several days, up to 3-4 weeks. Once the moisture reappears, a maintenance treatment should be carried out. Some patients undergo treatment regularly once a week as a preventive measure.
The classical iontophoresis treatment is performed with direct current (DC) of constant intensity. On feet and hands this has been for decades and still is a very reliable treatment for many patients. Under certain circumstances this type of current may cause unpleasant sensations or even pain at higher current levels, maybe before reaching a level necessary for effective treatment. This happens particularly in areas where the skin is very sensitive (armpits, face, etc.) or when there are small skin lesions. Some people do not tollerate the treatment because generally more sensitive, such as children.
Therefore, devices have been developed that deliver direct current in intermittent pulses of certain frequency. This type of current is much less perceived and therefore, at the same amperage, far better tolerated. The patient accepts a higher amount of energy and can therefore expect a much better effect. Unfortunately, this advantage comes at a higher price.
Iontophoresis for palmar hyperhidrosis
Iontophoresis for plantar hyperhidrosis
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Examples of different devices
Iontophoresis is performed at home with home-therapy equipment. For availability of equipment see below.
In medicine, the principle of iontophoresis is often used to get pharmaceutical substances through the skin with the help of electrical current, aiming to achieve high concentrations and a maximum effect of the drug locally, and minimizing the side effects in distant areas. The method is particularly useful in combating local painful and inflammatory conditions. Devices dedicated to drug-iontophoresis have a weaker output (5-10 mA). Iontophoresis for the treatment of hyperhidrosis should deliver at least 25-35 mA continuous DC and/or 15-25 mA for pulsating DC. If the treatment fails to yield acceptable dryness at highest tollerable current levels, a tiny dose of an anticholinergic drug (eg atropine) may be added to the water. However, such a measure should be carried out only under medical supervision in order to avoid toxicity by overdosing.
Ionophoresis is preferably performed at home with home-based therapy equipment.
It may be difficult to find the right device through pharmacies or healthcare providers. When purchasing online, it is advisable to contact specialized stores with a refund guarantee, e g the largest online supplier in Europe (www.iontodevice.com) and the US (www.sweating.com) for equipment and materials dedicated to hyperhidrosis, shipping worldwide.