Written and maintained by CASRAI Editorial Board
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General product and regulatory information only, not medical advice. Whether to use any iontophoresis device is a decision for a clinician and the device labeling.
Short answer
Iontophoresis is the passing of a weak electrical current through the skin (MedlinePlus, reviewed 3 June 2025). It is used to push charged drug molecules across the skin, to induce sweat for analysis, and, with tap water, to treat excessive sweating. In US regulation these uses sit under one device entry, 21 CFR 890.5525, which makes iontophoresis devices for purposes other than the sweat-induction use a prescription device.
Definition and scope
Roustit, Blaise and Cracowski describe iontophoresis as a non-invasive method of transdermal drug delivery based on the transfer of charged molecules under a low-intensity electric current (Br J Clin Pharmacol 2013;77(1):63-71). MedlinePlus lists excessive sweating of the hands, underarms and feet as a use and notes that home units are available.
The term covers three different product roles, which is why search results mix clinical, retail and laboratory pages:
- Sweat induction for analysis. 21 CFR 890.5525(a) covers a device used to induce sweat for analysis, for example in cystic fibrosis diagnosis, when the drug labeling gives adequate directions. FDA classifies it as Class II (performance standards).
- Tap-water units for sweating. DermNet NZ (page dated April 2015) describes passing current through skin soaked in tap water, with normal saline or an anticholinergic solution as other options.
- Drug-delivery electrodes and patches. Electrode assemblies that deliver a drug through the skin fall under the “any other purposes” paragraph of the same regulation.
How current moves substances
Roustit et al. name two main mechanisms.
Electromigration
Charged ions move across the membrane under the electric field. Negatively charged drugs are delivered under the cathode and positively charged drugs under the anode.
Electro-osmosis
The current also produces a volume flow from anode to cathode. It favours positively charged drugs and lets neutral molecules move during anodal iontophoresis.
The same review lists what governs delivery: the charge delivered (Faraday’s law), the current density (current divided by contact area), drug concentration (flux reaches a plateau), molecule size and charge, pH, and skin condition. For sweating, DermNet states that the mechanism is not fully understood; one theory is that ions block the sweat ducts in the stratum corneum.
Iontophoresis machines vs patches
“Machine” and “patch” describe different parts of the same system rather than competing technologies. Roustit et al. describe a controller connected by wires to an electrode patch. The electrodes are small sponges that conduct once dampened with the drug solution. They report that silver/silver chloride (Ag-AgCl) electrodes are preferred over bare metal or carbon because of a lower potential and because they avoid electrolysis of water.
DermNet describes two power types for sweating units: battery-powered direct current devices and mains-powered alternating current devices, with the hands placed in trays of water that hold the active and indifferent electrodes.
| Component or term | What the source says | Source |
|---|---|---|
| Controller | Generates the current and is wired to the electrode patch | Roustit et al. 2013 |
| Electrode patch | Sponge electrodes in skin contact, conductive once dampened with drug solution; Ag-AgCl preferred | Roustit et al. 2013 |
| Tray unit | Hands in water trays with active and indifferent electrodes; DC (battery) or AC (mains) types | DermNet NZ |
| Sweat-induction device | Class II (performance standards) under 890.5525(a) | 21 CFR 890.5525 |
How the FDA classifies iontophoresis devices
21 CFR 890.5525 (as published by Cornell Legal Information Institute) sets two tiers:
- Paragraph (a): a device for specified uses such as inducing sweat for analysis, when the drug labeling gives adequate directions, is Class II (performance standards).
- Paragraph (b): “An iontophoresis device intended for any other purposes is a prescription device.” It is Class II with special controls.
The special controls call for performance testing (safe use with an approved drug, safe pH, and mechanical safety if used in the ear), electromagnetic, electrical, thermal and mechanical safety testing, software verification, biocompatibility, sterility if supplied sterile, and shelf-life testing. The labeling must describe electrical output, electrode materials, the pH buffer, complications and warnings, and must carry this warning: “Potential systemic adverse effects may result from use of this device,” with a statement that drugs or solutions delivered with the device have the potential to reach the blood stream and cause systemic effects.
The regulation was issued in 1983 (48 FR 53047) and last amended in 2018 (83 FR 13864). Older 510(k) clearance letters may describe a different class for the “other purposes” category, so the current CFR text is the reference.
Where it matters for labs, clinics and supply decisions
This checklist is drawn from the regulation’s special controls. It lists what the labeling of a prescription iontophoresis device is required to state, so staff can see whether a document set covers it.
| Item to find in the labeling | Basis |
|---|---|
| Electrical output | 21 CFR 890.5525(b) labeling requirement |
| Electrode materials | 21 CFR 890.5525(b) labeling requirement |
| pH buffer | 21 CFR 890.5525(b) labeling requirement |
| Complications and warnings, including the systemic-effects warning | 21 CFR 890.5525(b) labeling requirement |
| Sterility statement, if the device is supplied sterile | 21 CFR 890.5525(b) special controls |
| Shelf life | 21 CFR 890.5525(b) special controls |
Roustit et al. identify device reliability as the central safety issue: they report component faults that caused burns and a fentanyl overdose risk, which led to the market withdrawal of one system, and that burns were rarer and usually tied to operator error or to electrode or formulation choice, worse at the cathode where pH rises. For related regulatory background see what a medical device is, predicate devices and substantial equivalence, FDA unique device identifiers, FDA recognized consensus standards, and medical device reporting.
Common misunderstandings
- “Iontophoresis” means one product. It is a technique with several product roles, and the regulatory status depends on the intended use.
- A home unit and a drug-delivery system are interchangeable. The regulation separates sweat-induction uses from “any other purposes,” which is a prescription device.
- It is risk-free because it is non-invasive. MedlinePlus says side effects are rare but may include skin irritation, dryness and blistering. Roustit et al. report tingling, erythema and edema as common and burns as rarer.
- Delivery rises indefinitely with concentration. The review reports that flux reaches a plateau.
FAQ
What is an iontophoresis machine?
It is a current-generating controller with electrodes. Sweating units use water trays with active and indifferent electrodes and may be battery-powered DC or mains-powered AC (DermNet NZ). Drug-delivery systems pair a controller with an electrode patch (Roustit et al. 2013).
What is an iontophoresis patch?
It is the electrode assembly of a drug-delivery system: sponge electrodes in contact with the skin that conduct once dampened with the drug solution, wired to a controller (Roustit et al. 2013).
Is an iontophoresis device regulated by the FDA?
Yes. 21 CFR 890.5525 classifies it as Class II, and a device for any purpose other than the listed sweat-induction use is a prescription device.
Sources
- 21 CFR 890.5525, Iontophoresis device, law.cornell.edu/cfr/text/21/890.5525 (checked 30 October 2026).
- Roustit M, Blaise S, Cracowski JL. Trials and tribulations of skin iontophoresis in therapeutics. Br J Clin Pharmacol 2013;77(1):63-71, PMC3895348 (checked 30 October 2026).
- DermNet NZ, Iontophoresis (page dated April 2015), dermnetnz.org/topics/iontophoresis (checked 30 October 2026).
- MedlinePlus, Iontophoresis (reviewed 3 June 2025), medlineplus.gov/ency/article/007293.htm (checked 30 October 2026).
