A seizure is a sudden burst of uncontrolled electrical activity in the brain that temporarily changes how you move, feel, behave, or think. Seizures can last anywhere from a few seconds to several minutes, and they range from brief moments of staring blankly into space to full-body convulsions. About 1 in 10 people will have at least one seizure during their lifetime, and having a single seizure doesn’t necessarily mean you have epilepsy.
What Happens in the Brain During a Seizure
Your brain cells communicate through carefully timed electrical signals. During a seizure, large groups of neurons start firing all at once in a rapid, synchronized pattern that overwhelms normal brain function. Think of it like a power surge in an electrical grid: the overload disrupts the circuits that control movement, sensation, awareness, or emotions, depending on where in the brain the surge occurs.
Some seizures start in one specific area of the brain and stay there. Others begin in one spot and spread across both sides. A third type involves abnormal electrical activity across the entire brain from the very start. Where the seizure originates and how far it spreads determines what you experience, which is why seizures can look so different from person to person.
Types of Seizures
Seizures fall into two broad categories based on where the abnormal electrical activity begins.
Focal Seizures
Focal seizures start in one specific region of the brain. If you remain aware during the episode, you might notice unusual sensations: a sudden strange taste or smell, tingling in one hand, a wave of fear or déjà vu, or involuntary jerking on one side of your body. These episodes typically last under two minutes.
When a focal seizure affects your awareness, you may appear conscious but be unresponsive. People in this state often perform repetitive movements like lip smacking, hand rubbing, or fumbling with clothing. Afterward, you likely won’t remember what happened during the episode.
Generalized Seizures
Generalized seizures involve both sides of the brain simultaneously and almost always cause a loss of awareness. The most recognized type is a tonic-clonic seizure (formerly called grand mal), where the body stiffens, you lose consciousness, and your muscles begin jerking rhythmically. These usually last one to three minutes. If one continues beyond five minutes, it’s a medical emergency.
Not all generalized seizures involve convulsions. Absence seizures cause brief lapses in awareness, sometimes just 5 to 10 seconds, where a person stares blankly and may flutter their eyelids. These are especially common in children and can happen dozens of times a day, often mistaken for daydreaming. Other types include myoclonic seizures (sudden, brief muscle jerks) and atonic seizures (a sudden loss of muscle tone that can cause you to drop to the ground).
Common Causes and Triggers
Many things can provoke a seizure, even in people who don’t have epilepsy. High fevers in young children are one of the most common causes, affecting about 2 to 5 percent of kids under age five. These febrile seizures are usually harmless and don’t lead to epilepsy later in life.
Other causes include head injuries, stroke, brain infections like meningitis or encephalitis, brain tumors, and very low blood sugar. Alcohol withdrawal is a well-known trigger, particularly in people who have been drinking heavily for an extended period and stop abruptly. Severe sleep deprivation, certain medications, and drug use (especially stimulants) can also lower the seizure threshold.
For people with epilepsy, everyday triggers can make seizures more likely. These include missed medications, stress, lack of sleep, illness, flashing lights (in a specific type called photosensitive epilepsy), hormonal changes during menstruation, and skipping meals. Identifying your personal triggers is one of the most practical steps in managing recurrent seizures.
What a Seizure Feels Like
Some people experience warning signs minutes or hours before a seizure, sometimes called an aura. An aura is actually a small focal seizure itself, and it can produce a rising sensation in the stomach, a sudden emotional shift, visual disturbances, or an odd smell that isn’t there. Not everyone gets auras, but for those who do, they can serve as a signal to get to a safe place.
During a tonic-clonic seizure, you’re unconscious and won’t remember the event. Afterward, most people enter a postictal state: a recovery period marked by confusion, exhaustion, headache, muscle soreness, and sometimes difficulty speaking. This phase can last minutes to hours. Some people feel emotionally off for a day or two after a major seizure.
Focal seizures with preserved awareness can feel deeply strange. People describe them as dreamlike, with distorted perceptions or emotions that come on without any apparent reason and then fade. Because you’re conscious throughout, the experience can be disorienting even though it’s brief.
Seizures vs. Epilepsy
A single seizure is not epilepsy. Epilepsy is diagnosed when a person has two or more unprovoked seizures at least 24 hours apart, or when a single seizure occurs alongside brain findings (such as abnormal activity on an EEG or structural changes on an MRI) that suggest a high risk of more seizures. Roughly 3.4 million people in the United States live with epilepsy.
Provoked seizures, those caused by a clear, temporary trigger like a high fever, alcohol withdrawal, or an acute head injury, don’t count toward an epilepsy diagnosis. The distinction matters because epilepsy requires ongoing management, while a provoked seizure may never happen again once the trigger is resolved.
How Seizures Are Diagnosed
After a first seizure, the primary tool is an electroencephalogram (EEG), which records electrical activity in your brain through sensors placed on your scalp. The test is painless and takes about 30 to 60 minutes. Doctors look for abnormal patterns that indicate where seizures may be originating and whether you’re at risk for more.
Brain imaging, usually an MRI, helps rule out structural causes like tumors, scarring, or blood vessel abnormalities. Blood tests check for metabolic issues such as low sodium, low blood sugar, or signs of infection. If the seizure was clearly provoked, for example by a known medication reaction, further testing may not be necessary.
Treatment and Management
Anti-seizure medications are the first-line treatment for epilepsy and successfully control seizures in about two-thirds of people. Finding the right medication can take time, because different seizure types respond to different drugs, and side effects like drowsiness, dizziness, or mood changes sometimes require switching to an alternative. Most people take medication daily, and stopping abruptly can trigger breakthrough seizures.
For the roughly one-third of people whose seizures don’t respond well to medication, other options exist. Surgery to remove or disconnect the brain area causing seizures is effective for certain types of focal epilepsy. Nerve stimulation devices, which send mild electrical pulses to the brain through a small implant, can reduce seizure frequency. Specialized diets very high in fat and low in carbohydrates have also shown benefit, particularly in children with hard-to-treat epilepsy.
Lifestyle adjustments make a real difference. Consistent sleep schedules, stress management, avoiding known triggers, and wearing medical identification are all practical tools. Many people with well-controlled epilepsy drive, work, and live without significant restrictions, though laws around driving after a seizure vary by state and typically require a seizure-free period of 3 to 12 months.
How to Help Someone Having a Seizure
If you see someone having a tonic-clonic seizure, the most important things are to keep them safe and let the seizure run its course. Ease them to the ground, turn them gently onto one side to keep the airway clear, and move hard or sharp objects away. Time the seizure from start to finish.
Do not put anything in their mouth. People cannot swallow their tongue during a seizure, and placing objects between the teeth risks broken teeth or injury to you. Do not hold them down or try to stop the movements. Stay with them until they are fully alert and oriented, and call emergency services if the seizure lasts longer than five minutes, if another seizure follows quickly, if the person doesn’t regain consciousness, or if it’s their first known seizure.