Iontophoresis: only one hand was treated — and the other hand improved just as much

A 2023 randomised controlled trial in Iran. Thirty-two patients with primary palmar hyperhidrosis were divided into two groups of sixteen.

• Group 1: iontophoresis with aluminium chloride hexahydrate gel
• Group 2: iontophoresis with tap water
• On the dominant hand only, seven sessions every other day
• Sweating rate measured by gravimetry and iodine-starch test before and after the last session

The result.

Following iontophoresis, the rate of sweating in both hands in the two groups was significantly reduced (P < .001). However, the sweating rate in the treated hand and the non-treated hand showed no significant difference.

Read that second sentence again.

Current went through one hand only, and the other hand lost just as much sweat. And the difference between them was not statistically distinguishable.

This is where the design earns its value. The untreated hand acted, in effect, as a control group attached to the same body. Same person, same day, same expectation, same measurement conditions — the only difference was whether current was applied.

And that one difference did not separate the results.

So why did both sides fall? Several possibilities.

• A systemic effect — current through one side may have altered sympathetic activity throughout the body
• Time and regression to the mean — people who enrolled at their sweatiest may have drifted back to their own average over two weeks
• Measurement conditions — gravimetry swings heavily with room temperature, humidity and tension. Participants may simply have been less nervous by the end

This trial alone cannot separate them. So this item is filed as 'not established'.

It was 32 people, over seven sessions every other day.

What the trial compared was aluminium chloride gel iontophoresis against tap water iontophoresis.

Tap water iontophoresis is not a placebo. It is one of the standard methods long used for palmar hyperhidrosis, and the current flows just the same. So the design asked 'does adding a drug help', not 'does iontophoresis work'.

It is the structure we keep writing about on procedure pages here — as the hyaluronic acid filler page sets out, almost every randomised trial in this field is A versus B.

But here the situation from the item above overlaps. Normally 'A versus B, no difference' means you cannot tell whether both worked or neither did. This trial, though, had a third point of comparison — the untreated hand — and that hand improved just as much.

So what the trial actually showed is this:

• Does aluminium chloride gel beat tap water — no (no significant difference)
• Does the hand that had iontophoresis beat the hand that did not — no (no significant difference)
• Did sweating fall in both hands over two weeks — yes (P < .001)

Quote the third line alone and the procedure reads as effective. Keeping all three lines together is what this page is for.

We found no randomised trial comparing iontophoresis against a sham — that is, against the same setup with the current off.

Building a sham here would not actually be hard: put the hands in the same device and switch off the current. Participants might notice the absence of tingling, but that can be handled by passing a very weak current — the same approach the radiofrequency plus HIFEM trial used when it set its sham arm to 5%.

And yet we found no such trial.

The gap stands out more when you look across the same sweating concern.

• Botulinum toxin — 322 people, 52 weeks, placebo-controlled
• Microwave — sham-controlled
• Iontophoresis — no sham control

We have also registered a 2022 systematic review of palmar hyperhidrosis in this page's sources. We have not verified at source what that review concluded about iontophoresis, so we do not carry its content over here.

What is not established, written as it stands:

• Whether iontophoresis beats doing nothing — not established
• How many sessions are appropriate — not established
• How long any effect lasts — not established
• Whether home devices match clinic devices — not established

Having been used for a long time and having evidence are different things. The cryolipolysis page carries the same sentence.