You put your hands or feet in trays of ordinary tap water. A machine sends a weak direct current between two electrodes through the water and through your skin. The current is small, and you control the level yourself.
The honest answer to how it works is that nobody has settled it. The leading idea is that the current temporarily plugs or disables the sweat duct where it opens onto the skin, so sweat produced deeper down cannot get out. Other theories involve a local change in the acidity of the duct or a direct effect on the nerve endings that trigger the glands. What is clear is that the effect is local, it builds over repeated sessions, and it fades if you stop.
Two practical consequences follow. First, it only helps the parts you put in the water, which is why it suits palms and soles and is awkward everywhere else. Second, because it is not destroying anything, it must be repeated forever. That is not a failure of the treatment; it is how it works.
Very soft water sometimes carries too little current to be effective. A pinch of baking soda in the tray is the usual fix. For people who stall out on tap water alone, some dermatologists add a small amount of a glycopyrrolate solution to the water, which often pushes a partial responder over the line.
Tell your dermatologist about any implanted device, metal hardware, pregnancy or heart rhythm problem before your first session.
Ask for a prescription and a letter of medical necessity if you plan to buy a machine. Some insurance plans and many flexible spending accounts will cover it, and the paperwork is much easier before you buy than after.
Remove rings, watches and any jewelry from the area. Metal concentrates current and causes stinging.
Cover cuts, cracks and hangnails with a dab of petroleum jelly. This is the difference between a comfortable session and a painful one.
Fill the trays with plain tap water, just deep enough to cover the palms or the soles. Do not use distilled water — it does not conduct.
Do not use a metal bowl or sit with your feet touching anything metal.
You place both hands, or both feet, in the trays, with the electrode plates sitting under the water.
You turn the current up slowly from zero until you feel a distinct tingle that is noticeable but not painful. That level is different for everybody and is different on hands and feet. Hands tolerate less than feet.
The tingling is the point. Turning the machine to a level you cannot feel means the session will do nothing. Turning it to a level that hurts risks small burns at any break in the skin.
A typical session runs 20 to 30 minutes. Most machines switch the direction of the current partway through so that both hands or both feet get treated evenly — some do this automatically, some need you to flip a switch.
You will feel pins and needles, occasional small sharp pricks where there are unnoticed nicks, and sometimes a metallic taste. The sharp pricks mean current is finding a break in the skin. Turn the current down and add petroleum jelly there next time.
Turn the current back to zero before taking your hands or feet out. Lifting them out with the current running gives you an unpleasant jolt.
Afterward, dry off and moisturize. You can do anything you like immediately.
There is no recovery period. You go straight back to whatever you were doing.
Hands and feet often feel dry, and sometimes a little rough or tight, for a few hours. A plain moisturizer or petrolatum at the end of the session handles that.
Small red dots or a faint prickle where the current found a nick are common and settle within a day.
The schedule, not the recovery, is the demanding part. A typical plan is a session every day or every other day for two to four weeks until the sweating drops, then a maintenance session every one to two weeks. If you find yourself getting wet again before the next session, move maintenance closer together rather than turning the current higher.
Most people who use it correctly get a substantial reduction in palm and sole sweating. It is one of the more reliable treatments in hyperhidrosis, and it has been in routine use for decades.
The improvement builds. The first few sessions may do very little. Judge it after three to four weeks of frequent sessions, not after two.
What "working" looks like: hands that can hold paper, shake hands and use a phone screen without wiping. Not completely dry hands. People who set the bar at zero sweat generally end up disappointed.
It always comes back. Stop for two or three weeks and you are usually back where you started. Restarting works, and you generally get back to dryness faster the second time.
Who is disappointed: people who do a handful of sessions and quit, people who keep the current too low to feel, people with severe sweating who never try adding glycopyrrolate to the water, and people expecting it to help their face or trunk.
If tap water alone stalls, the usual next steps are adding a glycopyrrolate solution to the water, or moving to Botox injections into the palms, oral glycopyrrolate or oxybutynin. Nerve surgery is a distant last resort for reasons covered on the ETS surgery page.
Home use is the normal way to do this — it is not a compromise. Clinic sessions two or three times a week are impractical and cost more within a few months than buying the machine.
Get a real machine. Prescription-grade and reputable consumer units both work, and both are far safer than the improvised setups described on forums. Do not build one from a battery charger or a phone adapter. The current, the polarity switching and the safety cutoffs are what keeps this from burning you, and homemade rigs have caused injuries.
Ask your dermatologist for a prescription and a letter of medical necessity before you buy. Some plans cover it, most flexible spending and health savings accounts will, and a machine you use for a decade is one of the better-value purchases in dermatology.
The other genuinely useful home measures for sweaty hands and feet are aluminum chloride antiperspirants applied to dry skin at night (they work on palms and soles, not just underarms), moisture-wicking textiles and changing socks during the day.