When electric current passes through the human body, it disrupts the electrical signals your cells use to communicate, generates intense internal heat, and can override the heart’s rhythm in a fraction of a second. The severity depends on the voltage, the type of current (AC or DC), how long the contact lasts, and the path the electricity takes through your body. Here’s what actually happens at each stage.
Why You Can’t Let Go
Your muscles contract and relax in response to tiny electrical signals from your nerves. When an outside current enters your body, it hijacks that signaling. At around 16 milliamps of alternating current, the average adult male loses the ability to voluntarily release his grip on a conductor. At 22 milliamps, more than 99% of adults physically cannot let go. Women and smaller individuals may lose muscle control at currents as low as 10 milliamps.
This “let-go threshold” is one of the most dangerous features of AC shock. The alternating current causes muscles to contract and relax rapidly, locking the hand around whatever is delivering the shock. The longer you’re locked on, the more current flows and the more damage accumulates. DC shock can throw you away from the source with a single violent muscle contraction, which is traumatic but sometimes limits total exposure time.
At about 20 milliamps, the muscles that control breathing can go into sustained contraction, effectively paralyzing the diaphragm and chest wall. If the current stops in time, breathing may resume on its own. If it doesn’t, suffocation begins within minutes.
What Happens to the Heart
The heart runs on its own finely tuned electrical system. Current passing through the chest can throw that system into chaos. The most common lethal event is ventricular fibrillation, where the heart’s lower chambers quiver uselessly instead of pumping blood. Alternating current at household frequency (50 or 60 Hz) is particularly efficient at triggering this. Research comparing AC and DC in the same heart tissue found that AC’s fibrillation threshold is roughly three times lower than DC’s, meaning it takes far less AC to send the heart into a fatal rhythm.
Even after fibrillation is corrected (by a defibrillator, for instance), the breathing muscles may still be paralyzed from the shock. Without assisted ventilation, oxygen levels drop and the heart can arrest a second time from lack of oxygen. This is why rescue breathing is critical even after a pulse returns.
Burns That Start From the Inside
Electrical burns are fundamentally different from flame or contact burns. Current flowing through tissue generates heat according to a straightforward physics principle: heat equals the resistance of the tissue multiplied by the square of the current, multiplied by time. Bone has higher resistance than muscle, so it heats up more. This means the worst thermal damage often happens deep inside the body, around bones and joints, while the skin may look relatively intact.
The CDC distinguishes two main types of electrical burns. True electrical burns result from current flowing directly through tissue. Arc burns happen when high-amperage current jumps through the air between a source and the body, producing temperatures that can exceed several thousand degrees. Arc flashes can ignite clothing and cause conventional thermal burns on top of the electrical injury, creating a layered pattern of damage that complicates treatment.
Because the deepest injuries are invisible from the surface, electrical burns are notoriously difficult to assess. A person with small entry and exit wounds on the skin can have extensive destruction of muscle, nerve, and blood vessel tissue along the current’s internal path.
Cell Membranes Break Apart
At the cellular level, strong electric fields punch holes in cell membranes through a process called electroporation. Cell membranes are designed to carefully control what enters and exits the cell. High-intensity fields disrupt that barrier, causing ions to leak out, metabolites to escape, and the internal chemistry of the cell to collapse. If the exposure is brief and the field strength is low enough, some cells can reseal. At higher intensities or longer durations, cells rupture entirely.
This membrane damage is part of why electrical injuries cause so much hidden destruction. Cells along the current path can die even without being heated to the point of charring, simply because their membranes no longer function.
Muscle Breakdown and Kidney Damage
When large amounts of muscle tissue are destroyed, whether by heat or by direct cellular disruption, the contents of those muscle cells spill into the bloodstream. One protein in particular, myoglobin, is toxic to the kidneys in large quantities. This condition, called rhabdomyolysis, develops in the hours and days after a significant electrical injury.
Acute kidney injury is the most serious complication of rhabdomyolysis, occurring in about 33% of patients. The kidneys become clogged with myoglobin while simultaneously receiving less blood flow due to fluid shifts in the body. Dark or cola-colored urine is a hallmark sign. The extent of muscle damage is often far greater than the external wounds suggest, which is why blood tests to measure muscle enzyme levels are a standard part of evaluating anyone with a significant electrical injury.
Neurological Effects, Immediate and Delayed
The nervous system is exquisitely sensitive to electrical disruption. In the immediate aftermath, loss of consciousness, confusion, seizures, and temporary paralysis are common. Current passing through the brain can suppress the respiratory center in the brainstem, which is one reason breathing may not restart on its own even after the heart does.
The longer-term picture can be equally serious. Permanent nerve damage at the entry site of the current is extremely common. Survivors frequently develop problems in one or more peripheral nerves, leading to numbness, weakness, or chronic pain in affected limbs. These symptoms can appear immediately or emerge months to years after the injury, with onset sometimes delayed by one to five years or more.
Cognitive and psychological effects are widespread among survivors. Difficulty with verbal memory, reduced attention span, trouble with executive functioning (planning, organizing, problem-solving), and behavioral changes are all well-documented consequences. One study found that as many as 78% of electrical injury survivors meet the criteria for a psychiatric diagnosis afterward. These aren’t signs of weakness or anxiety about the event. They reflect physical damage to the brain and nervous system caused by the current itself.
Why the Path Through the Body Matters
Not all shocks are equal, even at the same voltage. Current entering one hand and exiting the other passes directly through the chest, crossing the heart. A hand-to-foot path also involves the torso. A shock that travels only through one finger, while painful and capable of causing a local burn, is far less likely to trigger a fatal heart rhythm.
Moisture dramatically changes the equation. Dry skin has relatively high resistance and can limit current flow. Wet skin, sweat, or submersion in water drops that resistance substantially. Testing in water has shown that currents as low as 8 to 12 milliamps can cause involuntary muscle contractions strong enough that a person cannot overcome them, which is part of why electrocution in bathtubs and swimming pools is so dangerous.
Contact duration is the other critical variable. A brief static shock delivers current for microseconds. Grabbing a live wire with a wet hand while standing on a grounded surface can deliver current continuously, and every additional second increases heat generation, cellular damage, and the probability of cardiac arrest.