Direct current and galvanization. Physical characteristics and biological effects. Techniques and methods of application. Dosage, indications, contraindications, and safety considerations

Direct current and galvanization. Physical characteristics and biological effects. Techniques and methods of application. Dosage, indications, contraindications, and safety considerations

Galvanization is treatment with a steady direct current. This page covers what such a current is, what it does to ions, water, membranes and blood flow under each electrode, the electrodes and methods (stable, labile, rhythmic, local, segmental, general), how the dose is set, and when it is and is not used.

Contents8 sections

At a glance

  1. A galvanic current is a direct current: it flows one way, at a steady strength, at 0 Hz. Low voltage (up to about 150 V) and small currents (usually a few milliamperes) are used.
  2. In tissue it moves ions: cations to the cathode, anions to the anode. Electrolysis makes alkali under the cathode and acid under the anode, and water drifts towards the cathode.
  3. The cathode depolarises membranes and stimulates; the anode hyperpolarises them and calms. Both produce reddening and better blood flow, more under the cathode.
  4. Methods: stable (still electrodes, steady current), labile (one electrode moved), rhythmic (current switched on and off); local, segmental and general; named techniques such as the Shcherbak collar, galvanic shorts, Bergonié's half-mask, Vermel's general galvanization and hydrogalvanic baths.
  5. The dose is set by sensation: a light tingling, never burning or pain. Usually 5 to 25 minutes, 10 to 25 sessions, with a total current not above 50 mA.
  6. The main danger is a chemical burn under an electrode, deeper under the cathode. Areas without sensation, broken skin, metal in the path, pacemakers, tumours, bleeding, acute inflammation and pregnancy are kept away from it.
  7. Modern evidence for galvanization on its own is thin. Its lasting importance is that it is the basis of iontophoresis and of every current with a direct-current component.

Direct current and galvanization

Electrotherapy began with direct current. A galvanic current (after Luigi Galvani) is a continuous current that keeps its direction, polarity and strength the whole time it flows. It has no frequency: it is 0 Hz. Galvanization is its therapeutic use.

Picture a river that flows one way at an even speed. Nothing pulses, so nerves are not fired over and over. What changes instead is where the charged particles of the tissue end up, and that is where all its effects come from.

Physical characteristics

FeatureGalvanic current
DirectionOne way, from anode (+) to cathode (−) in the external sense; inside the body, cations move to the cathode and anions to the anode
AmplitudeConstant, usually 1 to 10 mA on the device (depends on electrode size and the patient)
VoltageLow, up to about 150 V
FrequencyNone (0 Hz)
SwitchingRamped up and down slowly, because a sudden change in a direct current fires nerves (a jolt)
ElectrodesConductive rubber or carbon, or metal plates, always over a thick wet pad

Where it acts: the professor's zones

The book divides the path of the current into three zones, which explains why the effects are strongest under the electrodes.

ZoneWhereWhat happens
Polar zoneBetween electrode and skinElectrolysis, the products that burn
Peripolar zoneJust under the skin beneath each electrodeIon shifts, membrane polarisation, the specific effects
Interpolar zoneDeep, between the two peripolar zonesWeaker, nonspecific effects (hyperaemia, metabolism)

Inside the peripolar zones, cell membranes act as semi-permeable barriers on which ions pile up. Each acts like a tiny electrode of opposite polarity: the book calls them virtual electrodes. It is a model that explains why direct current does not act evenly, not a structure seen in tissue.

Biological effects

Physical and chemical effects

  1. 1

    Ions move

    Cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) drift to the cathode, anions (Cl⁻, HCO₃⁻) to the anode. Older texts add that the ratio of K⁺ and Na⁺ to Ca²⁺ and Mg²⁺ rises under the cathode, because single-charged ions move fastest; that holds for potassium, but sodium moves more slowly than calcium, so this is an old claim rather than a measured fact.
  2. 2

    Electrolysis

    At the electrodes, sodium and chloride ions give up their charge and react with water. Sodium hydroxide (alkali) forms under the cathode, with hydrogen gas; hydrochloric acid forms under the anode, with oxygen.
  3. 3

    Electro-osmosis

    The tissue's fixed proteins carry a negative charge, so the fluid around them carries a slight positive charge and drifts towards the cathode. Tissue under the cathode swells and loosens; under the anode it dries and firms.
  4. 4

    Membrane polarisation

    Charge piles up on cell membranes, changing how near threshold they sit.

The book adds two names for changes to large molecules in a direct-current field, electro-dimerisation and electro-polymerisation; they belong to the same list of polarisation phenomena.

Under the cathode and under the anode

Under the cathode (−)Under the anode (+)
MembraneDepolarised, catelectrotonusHyperpolarised, anelectrotonus
ExcitabilityRaised: nerve and muscle fire more easilyLowered
ChemistryAlkaline (pH up)Acidic (pH down)
WaterTissue swells and loosensTissue dries and firms
Blood flowMarked hyperaemiaHyperaemia, less marked
Classical effectIrritative: stimulating, trophic, resorptive, revulsiveInhibitory: analgesic, sedative, lowers tone, anti-oedema
Burn if overdosedAlkaline, liquefaction necrosis, deeperAcid, coagulation necrosis, superficial
A direct current in the tissue
A slice through the body: sand-coloured skin on top, a layer of cream fat cells below it, and rose muscle below that. On the skin sit two electrodes, each a pale plate on a wet pad: the cathode, marked minus, on the left, and the anode, marked plus, on the right. In the fat and muscle between them, teal balls drift with fading trails behind them: sodium ions and water molecules towards the cathode, chloride ions towards the anode. Along the top of the cathode's pad, just under the electrode where they form, sit hydroxide ions, the alkali; along the top of the anode's pad, hydrogen ions, the acid. Deep in the muscle a mauve nerve fibre runs under both electrodes, with plus signs along the outside of its membrane and minus signs inside. Under the cathode the fibre is paler and its charges are few: the membrane is depolarised. Under the anode it is deeper and its charges are crowded: the membrane is hyperpolarised.+−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−++−−+Na⁺Na⁺Na⁺Na⁺Cl⁻Cl⁻Cl⁻Cl⁻Cl⁻−+OH⁻OH⁻OH⁻OH⁻H⁺H⁺H⁺H⁺

Point at a name or a part to light it.

A direct current moves charge through the tissue, and everything it does follows from that. Cations drift to the cathode and anions to the anode; water drifts to the cathode too. At the electrodes, electrolysis makes alkali under the cathode and acid under the anode, which is why the pads must be thick and wet and why burns form there. Under the cathode the nerve membrane is depolarised and fires more easily (catelectrotonus); under the anode it is hyperpolarised and calmed (anelectrotonus).

Simplified: not to scale: the layers, the ions, the water molecules and the nerve fibre are drawn far larger than life, and the pads far thinner; the current spreads through the tissue between the pads, and the ions are shown drifting along it in a few directions; they move slowly, and most are carried along by many collisions; the charges on the membrane stand for its voltage, not for single ions; a real fibre has a myelin sheath and runs in a nerve with many others; a few ions stand for many kinds and countless numbers; potassium, calcium, bicarbonate and the gases of electrolysis are left out.

5 sources
  1. Aleksiev A. Physical Medicine and Rehabilitation for English-speaking MD students. Medical University of Sofia, 2002. Galvanization: biophysics, polarization phenomena, effects of the electrodes, hydrophile pillows.
  2. Aleksiev AR. Physical Medicine and Rehabilitation, lecture 1 handnotes. Medical University of Sofia, 2026. Galvanic current: ion migration, electro-osmotic flow, changes in tissue pH.
  3. Cameron MH. Physical Agents in Rehabilitation, an evidence-based approach to practice, 5th edition. Elsevier, 2018. Chapters on electrical currents and their effects.
  4. Hall JE, Hall ME. Guyton and Hall Textbook of Medical Physiology, 14th edition. Elsevier, 2021. Membrane potentials and action potentials.
  5. Rumble JR (ed). CRC Handbook of Chemistry and Physics, 104th edition. CRC Press, 2023. Equivalent conductivity of electrolytes in aqueous solution (limiting ionic conductivities).

Physiological effects

  • Hyperaemia. The skin reddens under both electrodes and stays red for some time after, because the current releases histamine-like substances and widens small vessels, more under the cathode. With it come warmth and a feeling of comfort. One lecture slide shows blood flow falling under the anode; the usual teaching is that the anode reddens the skin too, only less.
  • Electroanalgesia. The anode lowers the excitability of nerve endings; the current also activates large touch fibres, which damp pain in the spinal cord; and the better blood flow carries away pain-causing substances.
  • Effects on nerve and muscle. A steady direct current does not make a muscle contract; only switching it on, off or changing it suddenly does. This is why rhythmic galvanization (current interrupted) is used to stimulate.
  • Trophic and resorptive effects. Better circulation and tissue loosening are said to help healing, resorption of swelling and nerve regeneration. This rests on old observations more than modern trials.
  • Segmental and reflex effects. A current applied over a skin zone that shares a spinal segment with an organ (Zakharyin–Head zones) or over the neck and face is said to act on that organ and on the autonomic nervous system. These effects are weaker and nonspecific.

Techniques and methods of application

Electrodes and pads

  • The active electrode is the treating one, often smaller, so current density and effect are greatest under it. The indifferent electrode is larger, so its density and effect are lower. Both carry the same current.
  • Each sits on a hydrophilic pad of cloth, sponge or felt, about 1 cm thick and soaked in warm tap water or saline, larger than the electrode on every side. The pad takes up the acid and alkali formed by electrolysis, keeps them off the skin, and lowers skin resistance.
  • The skin is clean and intact; small scratches are covered with an insulating layer, because current crowds into them.

How the electrodes are placed

PlacementWhereEffect
TransverseOn opposite sides of a limb or jointCurrent crosses the tissue, so it reaches deep structures such as a joint
LongitudinalAlong the same surface, one above the otherCurrent runs along the well-conducting tissues; longer and more superficial
DiagonalAcross, at an angle, such as from neck to armFor a particular path, such as nerve root to limb

By how the current is given

  • Stable galvanization. Both electrodes fixed, current steady. The usual method, and the one for analgesia and sedation, with the anode active.
  • Labile galvanization. The indifferent electrode stays, the active one is slid slowly over the skin. A stronger, more stimulating effect, for larger areas.
  • Rhythmic galvanization. Electrodes fixed, the current rises from zero to a set level and falls again in a rhythm. Each change fires nerves, so it stimulates: with the cathode active, for the revulsive effect and muscle stimulation.

By where the effect is wanted

MethodAimExamples
LocalThe diseased area itselfA painful joint (transverse), a nerve trunk, a scar
Segmental and reflexThe spinal segment or a reflex zoneParavertebral electrodes for radicular pain of an arm or leg, intercostal neuralgia; skin zones of an organ; the neck for heart pain of spinal origin
GeneralThe whole bodyGeneral galvanization, hydrogalvanic baths

The named techniques

The book and slides show the classic Eastern European set; the exam may ask for them by name.

  • Galvanic collar (Shcherbak). A large shawl-shaped electrode over the neck and upper shoulders, the other on the low back: a segmental technique for the cervical sympathetic chain, used for headache, sleep problems and high blood pressure in the old school.
  • Galvanic shorts (Shcherbak). Electrodes over the upper thighs and buttocks with one on the low back, for the lumbar segments and the pelvis.
  • Half-mask of Bergonié. A three-lobed electrode over one half of the face, for facial (trigeminal) neuralgia and facial nerve palsy.
  • General galvanization (Vermel). A large electrode between the shoulder blades and two on the calves, for a general, calming effect.
  • Hydrogalvanic baths. The limbs (four-chamber bath) or the whole body sit in water through which the current passes. Water is the electrode, so contact is even.
  • Endonasal (intranasal-neck) technique. Small wet wicks in the nostrils, the other electrode on the back of the neck; a reflex technique once used for sinusitis, asthma and bronchitis.
  • Also: transverse and longitudinal techniques for joints, galvanization of the eyes (through a bath electrode), of the breast and of the submandibular glands.

Dosage

What the dose is made of

per session
5–25minutes
per course, daily or every other day
10–25sessions
the most the total current may reach, with large electrodes
50mA

The dose is the current, the time, the electrode area and the polarity together. Current divided by electrode area gives the current density; classic Eastern European texts keep it at no more than about 0.1 mA/cm² in adults (usually 0.05 to 0.1 for local techniques, less for general and segmental ones), and lower still in children.

Dosing by sensation

In adults the current is set by what the patient feels, a subjective dose.

  • Acceptable: a light tingling, pricking or mild itching under the electrodes.
  • Not acceptable: burning or pain, which warn of a chemical burn; reduce or stop at once.
  • The sensation of one person cannot be compared with another's, because skin resistance differs hugely between people. A therapist or parent cannot test the current on themselves.
  • In an area with poor or no sensation (hypoaesthesia, anaesthesia, dysaesthesia), the patient's feeling there is no guide. The tolerated intensity is found on an intact area, best the opposite side, used as a cautious reference, and the skin is watched.
  • In children the dose is objective: a current density in mA/cm² from age-based tables, never only what the child says.

Monitoring

The current is raised slowly from zero and lowered slowly to zero at the end; the electrodes are never removed while current flows. Mild redness under the electrodes afterwards is normal; blisters, grey or brown spots are burns.

Indications

The book says galvanic current is used mainly for its analgesic effect. The lecture adds the other traditional uses. Most come straight from the polarity rule.

Because it…It is used forUsual active electrode
Calms nerve endings and relieves painNeuralgias (post-traumatic, post-herpetic, intercostal, trigeminal), radicular pain, sprains and strains, painful joints, myofascial pain and trigger pointsAnode
Lowers toneMuscle spasm, raised tone, hyperexcitabilityAnode
Raises excitability and blood flowMuscle weakness and disuse, peripheral nerve lesions (with other methods), poor local circulationCathode
Improves tissue nutritionSlow-healing wounds and ulcers, trophic disorders (as an adjunct)Cathode
Acts on segments and the autonomic systemAutonomic dysfunction, functional disorders (old school, weak evidence)Segmental techniques
Moves ionsDelivering drugs: see iontophoresisSame sign as the drug

Contraindications

They follow from three facts: direct current burns, it increases blood flow and tissue activity, and it flows wherever the electrodes send it.

ReasonDo not use (or only with great caution)
It burns, and the skin must warn usBroken, infected or inflamed skin under the electrodes; eczema and dermatitis; an area without sensation; a patient who cannot cooperate or report pain
It increases blood flow and tissue activityMalignant tumours; bleeding tendency, coagulation disorders, active bleeding; acute inflammation or trauma until the first reaction has settled; suppuration of any kind; active tuberculosis; fever and acute infection; acute deep vein thrombosis and venous obstruction; severe arterial insufficiency; active inflammatory arthritis with a swollen joint
It flows where it is sentA pacemaker or implanted defibrillator; metal implants in the current path, where current crowds and electrolysis acts on the metal; pregnancy, especially the abdomen, pelvis and low back; epilepsy (for the head)
The body may not copeSevere heart, lung, kidney or liver failure (use sparingly, if at all); frail and elderly patients with care

Safety

  1. 1

    Before

    Check contraindications and implants, test sensation, inspect the skin, explain that only a light tingling is allowed.
  2. 2

    Pads

    Wet, thick, larger than the electrode, never folded; no metal touching the skin; small scratches covered.
  3. 3

    Current

    Check polarity, start from zero, raise slowly, stay with the patient and ask.
  4. 4

    End

    Lower to zero before removing the electrodes, inspect the skin, record polarity, current, area, time and any reaction.

What causes burns: too high a current density (small electrode, high current), too long a session, thin or dry pads, an electrode touching the skin directly, a patient who cannot feel, reactive metal electrodes, and occlusive coverings that trap the products. Other adverse effects are skin irritation and itching, and, rarely, dizziness or a vasovagal faint.

Check yourselfAnswer, then say how sure you were: a lucky guess still counts as a weak point.

1After galvanization a patient has a soft, moist, greyish skin lesion with ragged edges under one electrode. Under which electrode did it most likely form, and why?

2In the classical method, which arrangement is chosen for pain relief over a painful shoulder?

3A patient with a post-traumatic neuralgia of the forearm has reduced sensation in the area to be treated. How is the galvanic current dosed?

4To reach the inside of the knee joint with a galvanic current, how should the electrodes be placed?

5Which patient should not receive galvanization of the lumbar region?

Sources

  1. Aleksiev A. Physical Medicine and Rehabilitation for English-speaking MD students. Medical University of Sofia, 2002. Galvanization (definition, biophysics, polarization phenomena, danger of chemical burn, polar zones, virtual electrodes, physiological effects, effects of the electrodes, application technique, examples of galvanic techniques, dosing, indications, contraindications).
  2. Aleksiev AR. Physical Medicine and Rehabilitation, lecture 1 handnotes. Medical University of Sofia, 2026. Galvanic current, definition, tissue effects, electrochemical injury, local and segmental effects, application techniques, electrode arrangement, dosage and monitoring, indications, limitations and safety.
  3. Watson T, Nussbaum EL (eds). Electrophysical Agents, evidence-based practice, 13th edition. Elsevier, 2021.
  4. Cameron MH. Physical Agents in Rehabilitation, an evidence-based approach to practice, 5th edition. Elsevier, 2018. Electrical currents, direct current and iontophoresis.
  5. Robinson AJ, Snyder-Mackler L. Clinical Electrophysiology, electrotherapy and electrophysiologic testing, 3rd edition. Lippincott Williams and Wilkins, 2008.

Checked against its sources on 05 Nov 2026.