A lightning injury occurs after brief exposure to the very intense current of the strike.
Lightning delivers a massive electrical pulse over a fraction of a millisecond. The brief duration of the exposure frequently limits the damage to the outer layer of skin. In addition, lightning is much less likely to cause internal burns than generated electricity. However, it can kill a person by instantaneously short-circuiting the heart. Lightning can also damage the nervous system, including the brain. Lightning is the second most frequent cause of storm-related deaths in the United States, resulting in about 30 deaths and several hundred injuries each year. Some injuries result in permanent disability.
Lightning tends to strike tall or isolated objects, including trees, towers, shelters, flagpoles, bleachers, and fences. A person may be the tallest object in an open field. Metal objects and water do not attract lightning but easily transmit electricity once they are hit. Electricity from lightning can travel from outdoor power or telephone lines to electrical equipment or telephone lines inside a house.
Lightning can injure a person several ways:
After a person has been struck by lightning, the heart may stop beating (cardiac arrest) or may beat erratically. When the heart beats erratically, breathing often stops. The heart may beat again on its own, but if breathing has not restarted, the body is deprived of oxygen. The lack of oxygen and, possibly, nervous system damage can cause the heart to stop beating again.
Brain injury usually causes loss of consciousness. If brain damage is severe, coma may develop. Typically, the person awakens but does not remember what happened before the injury (amnesia). The person may be confused, think slowly, and have difficulty concentrating and remembering recent events. Personality changes may occur and can be permanent.
The eardrums are often perforated. Many eye injuries can develop, including cataracts. Often both legs become temporarily paralyzed, blue, and numb (keraunoparalysis). The skin may show no marks at all or may have minor burns that have a feathering, branching pattern, consist of clusters of tiny pinpoint spots like a cigarette burn, or consist of streaks where sweat has been turned into steam. Numbness, tingling, and weakness may develop because the nerves branching out from the spinal cord have been damaged (peripheral neuropathy).
Lightning injuries are often witnessed, but they may also be suspected when a person is found outside unconscious or with amnesia during or shortly after a thunderstorm.
In the hospital, electrocardiography (ECG) may be done if injury is severe (for example, if a person collapsed and may have had a temporary cardiac arrest). The ECG, when done, determines whether the heart is beating normally. Sometimes blood tests or imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI), are needed.
During the thunderstorm season, listening to weather reports, which is particularly important for organizers of outdoor events, can help in deciding whether to cancel outdoor activities and in planning for any emergencies that may develop.
High winds, rain, and clouds may mean that a thunderstorm is imminent. By the time thunder is heard, the observers are already in danger and should be seeking safe shelter, such as a large habitable building or a fully enclosed metal vehicle (for example, a car, van, or truck) with the windows closed. Sheltering in a small open structure, such as a gazebo, is not safe. It is not safe to resume outdoor activities until 30 minutes after the last sound of thunder is heard or lightning is seen.
To prevent lightning injuries when indoors, people should avoid contact with plumbing or electrical wiring or using any hard-wired device, including a telephone, computer, video game console, or headsets attached by a cable to a sound system. Being away from windows and doors increases safety, as does turning off and unplugging electrical equipment before the thunderstorm arrives. Cellular telephones, tablet and laptop computers, and MP3 players are safe when used with battery power only because they do not attract lightning.
About 10% of people with lightning injuries die. The only cause of death is cardiac arrest and cessation of breathing at the time of the injury. People whose heartbeat and breathing resume survive. If memory of recent events is impaired or thinking is slow, the person may have permanent brain injury. Keraunoparalysis usually resolves within several hours, although the person may occasionally be left with weakness or clumsiness. People with nerve injury often have long-term problems, including chronic pain, sleep difficulties, and erectile dysfunction.
A person struck by lightning does not retain electricity, so there is no danger in providing first aid. People without a heartbeat and who are not breathing need cardiopulmonary resuscitation (CPR) immediately (see First-Aid Treatment), including both chest compressions and artificial respiration. If an automated external defibrillator (AED) is available, it should be used (Fig. 1: Automated External Defibrillator: Jump-Starting the Heart). A person who regains a pulse but still is not breathing needs continued artificial respiration because the respiratory muscles may stay paralyzed after the heartbeat returns. Emergency medical assistance should be called. Many people struck by lightning are in good general health and are more likely to recover if given timely CPR.
Burns and other injuries are treated as needed. If resuscitation efforts are not successful within the first 20 minutes, they are unlikely to be, so resuscitation efforts are then stopped.
Last full review/revision January 2015 by Daniel P. Runde, MD