What Causes Electrical Shock in the Human Body?

Electrical shock happens when current passes through body tissue, and the harm it causes depends on how much current flows, what path it takes, and how long the exposure lasts. Your skin normally acts as a strong barrier, but once current gets past it, the wet, salty tissues inside conduct electricity readily, allowing even modest voltages to disrupt the heart, lock up muscles, and burn tissue from the inside out. The story is more layered than “electricity is dangerous,” because the same household outlet that delivers a mild tingle in one scenario can kill in another.

Your Skin Is the Gatekeeper

More than 99% of the body’s resistance to electrical current sits in the skin. A dry, calloused hand can present over 100,000 ohms of resistance, mostly because of the thick layer of dead cells on the surface. Beneath that outer layer, internal body resistance drops to roughly 300 ohms, because living tissue is wet and full of dissolved salts that conduct electricity well.¹ This is why the circumstances of contact matter so much. A person with sweaty palms, a cut on their hand, or who is standing in water has lost most of that protective resistance. The same voltage that barely registers through dry skin can push dangerous amounts of current through wet or broken skin.

Think of it this way: voltage is the push, current is the flow, and resistance is the dam holding the flow back. Your skin is the dam. When the dam holds, very little current reaches your vital organs. When the dam breaks, current floods in. This is why electricians treat even modest household voltages with respect when their hands are wet or their skin is compromised.

Why the Path Through the Body Matters

The route current takes through the body is one of the biggest factors in whether an electrical shock is merely painful or life-threatening. A current path that crosses the chest, known as a transthoracic path, is the most dangerous because it can pass through the heart and the muscles that control breathing. Hand-to-hand, hand-to-foot, and front-to-back chest paths all qualify as transthoracic.² A shock that enters one hand and exits through the other hand travels straight through the heart. A shock that enters one hand and exits through the same arm is far less likely to cause cardiac arrest, though it can still burn tissue and lock up muscles along that limb.

Forensic data from electrocution fatalities reflects this pattern. In one study of 75 fatal cases, upper limb injuries were the most common entry point, found in about 39% of cases, and nearly half of victims had identifiable entry and exit wounds, confirming that current had traveled a defined path through the body.³ The path isn’t always predictable, though. Current follows the path of least resistance, which can branch and split through different tissues, making injury patterns sometimes surprising even to experienced clinicians.

What Current Does to Muscles and Nerves

Your muscles and nerves operate on their own tiny electrical signals. When an external current overrides those signals, the results can be dramatic. If enough current flows through a muscle, it forces the muscle to contract as fast as it can. Because muscle fibers can’t keep up with the rapid stimulation of household alternating current, the result is a sustained, locked contraction called tetany.⁴ This is the “can’t let go” phenomenon people describe: if you grab an energized wire, the flexor muscles in your hand clamp down involuntarily, and you physically cannot release your grip.

When this same tetanic contraction hits the muscles of the chest wall, breathing stops. The diaphragm and intercostal muscles lock up, and the person cannot inhale or exhale for as long as the current flows. If the exposure is brief, breathing may resume on its own once the source is removed. If it continues, the victim suffocates.² This respiratory arrest can kill even when the heart itself is unharmed, which is why rapid separation from the electrical source is the single most important first step in any rescue.

How Electrical Shock Stops the Heart

The most feared consequence of electrical shock is ventricular fibrillation, a chaotic, disorganized quivering of the heart muscle that stops it from pumping blood. Researchers have found that alternating current can trigger fibrillation by generating a rapid ventricular rate combined with uneven recovery of the heart muscle’s ability to respond to signals. An animal mapping study demonstrated that this happens because the electrical stimulation creates conflicting zones of excitability across the heart tissue.⁵ Once fibrillation starts, the heart cannot recover on its own without defibrillation, a deliberate counter-shock that resets the cardiac rhythm.

The threshold for triggering fibrillation decreases the longer current flows through the chest. Animal experiments have shown that even small currents can cause fibrillation if the exposure lasts long enough.² This is one reason household electricity is so dangerous: although the voltage is relatively low, a person who grabs a live wire and can’t let go may be exposed for many seconds, allowing the fibrillation threshold to drop well within the range of current that common circuits deliver.

Damage Beyond What You Can See

Electrical injuries are often compared to icebergs. The visible burns at the entry and exit points may look relatively small, while the real devastation lies deeper. As current passes through tissue, it generates heat through simple resistive heating, the same principle that makes a toaster wire glow. But heat isn’t the only mechanism of harm. Current also punches holes in cell membranes, a process called electroporation, and can directly warp the shape of proteins, destroying their ability to function.⁶

This means that tissue along the current path can be dead or dying even when the skin surface looks relatively intact. Surgeons treating electrical burn patients frequently describe finding layers of destroyed muscle beneath seemingly minor skin wounds. The deeper the tissue and the longer the current exposure, the more extensive this hidden damage tends to be. In a systematic review of direct current injuries, the most commonly reported consequences were burns and skin lesions, followed by neurological effects, unconsciousness, and cardiac complications.⁷

High-Voltage Injuries vs. Low-Voltage Injuries

The threshold between “high voltage” and “low voltage” in clinical practice is typically set at 1,000 volts, though some systems use different cutoffs. What matters is that high-voltage injuries tend to be dramatically worse across nearly every measurable outcome. A large propensity-matched analysis covering two decades of data found that high-voltage injuries were associated with roughly three times the amputation rate, more than five times the risk of death within 14 days, much longer hospital stays, larger burn areas, and a significantly higher likelihood of needing multiple surgeries compared to low-voltage injuries.⁸

But the data also tells a more nuanced story than “low voltage is safe.” Studies comparing the two groups have noted that low-voltage injuries still lead to reconstructive surgeries, and the number of operations required doesn’t always differ significantly between the groups.⁹ Household outlets deliver well under 1,000 volts, yet they remain responsible for a substantial share of electrical fatalities. In one forensic series, about two-thirds of electrocution deaths involved low-voltage sources.³ High voltage causes more tissue destruction, but low voltage kills through prolonged contact and cardiac disruption.

When Muscles Break Down and Kidneys Follow

One of the more insidious consequences of electrical injury, particularly from high-voltage exposure, is a chain reaction that starts in the muscles and ends in the kidneys. When electrical current destroys large amounts of muscle tissue, the damaged muscle fibers release their contents into the bloodstream. Among those contents is myoglobin, a protein that normally carries oxygen inside muscle cells. Flooding the bloodstream with myoglobin overwhelms the kidneys, which struggle to filter it out. The myoglobin constricts blood vessels in the kidneys, forms obstructive casts in the kidney’s filtering tubes, and directly damages kidney cells.¹⁰

This condition, called rhabdomyolysis, is estimated to affect about 10% of people who survive high-voltage electrical injuries. Acute kidney injury is its most serious complication.¹⁰ Doctors monitoring electrical injury patients watch blood levels of creatine kinase, an enzyme that spills out of damaged muscle, as an early warning sign. Aggressive fluid resuscitation, pushing large volumes of intravenous fluid to flush the kidneys, is one of the main treatment strategies. This is why electrical injury treatment in the hospital looks different from treating ordinary burns: the hidden muscle damage demands a different playbook.

Lightning as a Special Case

Lightning delivers staggering voltages and currents, yet not everyone struck by lightning dies. The reason is counterintuitive: the exposure is extraordinarily brief, and much of the current flows over the body’s surface rather than through it. A lightning flash can interact with a person through several mechanisms, including a direct strike, a side flash from a nearby object, touch voltage from holding something that gets hit, and step voltage from current spreading through the ground. The injuries a victim sustains depend heavily on which mechanism is involved and how much current actually penetrates the body.¹¹

Beyond the electrical current itself, lightning also produces intense light, extreme heat, and a powerful shock wave, all of which can cause independent injuries. Experimental work with animals exposed to simulated lightning impulses has shown that survival depends heavily on whether a flashover, where current arcs over the body’s surface, happens quickly. When the flashover occurred almost immediately after peak voltage, the animals survived because very little energy was deposited inside the body. When the flashover was delayed by even a fraction of a millisecond, enough energy passed through internal tissues to be lethal.¹² Essentially, your body’s own surface conductivity can save you from lightning if the current finds the outside path fast enough.

Microshock and the Hospital Setting

Most discussions of electrical shock assume current enters from outside the body and has to push through the skin. But in a hospital, catheters and electrode leads can deliver current directly to the heart muscle, bypassing the skin entirely. When that happens, the amount of current needed to trigger fibrillation drops to almost nothing. The accepted minimum current for cardiac fibrillation through a direct intracardiac path is just 10 microamps, which is one ten-thousandth of the current needed to produce the same effect through intact skin.¹³

This risk, called microshock, is why hospitals classify electrical equipment into safety categories depending on how close it gets to the patient’s heart. Equipment that contacts the body surface follows one set of leakage current standards; equipment with parts that can reach the heart, such as pacemaker leads or central venous catheters, follows far stricter limits. The entire grounding and isolation system in an operating room or intensive care unit is designed around the principle that a current too small for anyone to feel at the skin surface could be fatal if delivered directly to cardiac tissue.

Long-Term Neurological and Psychological Effects

Surviving an electrical injury doesn’t always mean recovering fully. Neurological symptoms are among the most widely reported consequences of both electrical and lightning injuries, and a disabling pattern of neuropsychological problems is commonly described in survivors.¹⁴ These can include difficulty concentrating, memory problems, chronic pain, and personality changes. The long-term effects tend to be more subtle and harder to define than the acute injuries, but they can be pervasive and disabling.¹⁵

A large register-based study comparing electrical injury survivors to matched controls found elevated rates of several mental health conditions. Post-traumatic stress disorder and anxiety disorders showed the strongest associations in the period shortly after injury, which isn’t surprising given the traumatic nature of the event. Depression was also more common, though with somewhat weaker associations. Some conditions took longer to emerge: somatoform disorders, sleep disorders, and other non-psychotic mental disorders appeared over a longer follow-up period.¹⁶ The picture that emerges is that electrical injury can set off a slow cascade of psychological consequences that outlasts the physical recovery by years.

Emergency Response to Electrical Shock

The immediate priorities in treating electrical shock victims are the same as for any cardiac arrest: secure the airway, support breathing, and restore circulation. But electrical injuries add several wrinkles. Vigorous fluid resuscitation is essential because of the hidden muscle damage and the risk of kidney failure described above. Spinal immobilization is often needed because tetanic muscle contractions and falls from heights are common accompaniments to electrical shock. And the standard triage rules for mass casualty events get reversed in lightning strike scenarios: with lightning, the people who appear dead, those in cardiac arrest, are prioritized for resuscitation because they may have the best chance of recovery if treated quickly, whereas in most other mass casualty events, victims without a pulse are triaged last.¹⁷

The reasoning behind that reversed triage is that lightning can cause temporary cardiac standstill that responds well to prompt CPR and defibrillation, while victims who are conscious and breathing after a lightning strike are unlikely to deteriorate rapidly. This is strikingly different from industrial or household electrical injuries, where the pattern of harm depends on contact duration and current path. In any electrical injury scenario, the first responder’s most important job, after ensuring the power source is off or the victim is safely separated from it, is to assume the worst about internal injuries and act accordingly.¹⁸

Who Gets Hurt Most Often

Electrical injuries are not evenly distributed across the population. Forensic and epidemiological data consistently show that young men, particularly those in occupational settings involving electrical work or construction, bear a disproportionate share of the burden. In one forensic analysis of electrocution fatalities, men accounted for 92% of victims, and the most common age group was 21 to 30 years old. The primary cause of death in that series was a combination of shock and subsequent infection.³ Children face a different risk profile: they are more likely to suffer electrical injuries at home from outlets, cords, and low-voltage appliances, and their thinner skin offers less resistance than an adult’s calloused hands.

Occupational electrical injuries also carry a particular psychological weight. The register-based study examining mental health outcomes found that the strongest risk estimates for psychiatric conditions appeared when electrical injury survivors were matched to controls in the same occupation, suggesting that the injury itself, rather than general occupational hazards, drives the elevated rates of PTSD and anxiety.¹⁶ For workers who survive a serious shock on the job, the physical recovery is often just the beginning of a longer process of psychological rehabilitation that workplaces and healthcare systems aren’t always equipped to support.

1
PubMed Central. Conduction of Electrical Current to and Through the Human Body: A Review – Section: Skin resistance protects the body from electricity
2
PubMed Central. Conduction of Electrical Current to and Through the Human Body: A Review – Section: Current path
3
Indian Journal of Forensic Medicine & Toxicology. Forensic Analysis of Electrical Injury Patterns: A Study of Electrocution Fatalities at SMS Medical College Jaipur
4
PubMed Central. Conduction of Electrical Current to and Through the Human Body: A Review – Section: Alternating and direct current
5
Heart Rhythm Open. The electrophysiology of electrocution – Section: Experimental Data Post-Einthoven
6
PubMed. Biophysical injury mechanisms in electrical shock trauma
7
ScienceDirect. Direct current electrical injuries: A systematic review of case reports and case series – Section: RESULTS
8
PubMed. Association between high- and low-voltage electrical injuries and adverse outcomes: a propensity-matched analysis (2002-2022)
9
PubMed Central. Electrical burn injury: a comparison of outcomes of high voltage versus low voltage injury in an Indian scenario – Section: Abstract
10
PubMed Central. High-voltage electrical injury complicated by compartment syndrome and acute kidney injury with successful limb salvage: A case report and review of the literature – Section: Discussion
11
Journal of Electrostatics. Lightning caused injuries in humans – Section: Abstract
12
Burns. Lightning injury caused by discharges accompanying flashovers—a clinical and experimental study of death and survival – Section: Abstract
13
International Journal of Anesthetics and Anesthesiology. Electrical Safety Symbols Used in Medical Equipment and Their Implication – Section: Microshock
14
PubMed Central. Neurological and neuropsychological consequences of electrical and lightning shock: review and theories of causation – Section: Abstract
15
PubMed Central. Long-term sequelae of electrical injury – Section: Main message
16
PubMed Central. Mental disorders following electrical injuries—A register-based, matched cohort study – Section: Results
17
PubMed. Electrical shock and lightning strike
18
The Journal of Emergency Medicine. Emergency medicine in review Electric shock, part III: Deliberately applied electric shocks and the treatment of electric injuries – Section: Abstract