A seizure trigger is a factor that can cause a seizure in a person who either has epilepsy or does not. There are many known causes of seizures, and in some patients, it is possible to determine what triggers seizures in general or has led to the onset of a particular seizure. But the factors that lead to a seizure are often so complex that it is not usually possible in all patients to determine what causes a particular seizure, what causes it to happen at a particular time, or how often seizures occur.
Alcohol consumption 
There are varying opinions on the likelihood of alcoholic beverages triggering a seizure. Consuming alcohol may temporarily reduce the likelihood of a seizure immediately following consumption. But after the blood alcohol content has dropped, chances may increase. This may occur, even in non-epileptics.
Heavy drinking in particular has been shown to possibly have some effect on seizures in epileptics. But studies have not found light drinking to increase the likelihood of having a seizure at all. EEGs taken of patients immediately following light alcohol consumption have not revealed any increase in seizure activity.
Consuming alcohol with food is less likely to trigger a seizure than consuming it without.
Consuming alcohol while using many anticonvulsants may reduce the likelihood of the medication working properly. In some cases, it may actually trigger a seizure. Depending on the medication, the effects vary.
Alcohol withdrawal 
Caffeine use can increase the occurrence of seizures, particularly if it interrupts normal sleep patterns.
Diet can play a role in a seizure occurring, and therefore, diet control in some cases can be used to prevent seizures. It is not known exactly what nutrients or lack thereof may contribute to or prevent a seizure. However, the ketogenic diet is practiced by some in order to control seizures.
Those with various medical conditions may suffer seizures as one of their symptoms. These include:
- Arteriovenous malformation
- Brain abscess
- Brain tumor
- Multiple sclerosis
- Systemic lupus erythematosus
Some drugs may lower the seizure threshold when used doses intended for recreation. Drugs such as tramadol and methamphetamine have been noted to induce seizures in some, especially when used for long periods of time or in combination with other stimulants. Some drugs may reduce the risk of a seizure occurring. Withdrawals from drugs that act on the GABA receptors may lead to grand-mal seizures in people who have been heavily abusing drugs from the barbiturate or benzodiazepine families.
About 2-5% of all children will experience such a seizure during their childhood. Most of these children will also have some pre-existing neurological problem.
In most cases, a febrile seizure will not lead to epilepsy. But 30-40% of children who experience a febrile seizure will have more seizures in the future.
In adults and older children with epilepsy, illnesses with fever can be responsible for a seizure due to the stress that they cause. Additionally, in some patients, gastroenteritis, which causes vomiting and diarrhea, can lead to diminished absorption of anticonvulsants, thereby reducing protection against seizures.
Flickering or flashing lights 
In some epileptics, flickering or flashing lights, such as strobe lights, can be responsible for the onset of a tonic clonic, absence, or myoclonic seizure. This condition is known as photosensitive epilepsy, and in some cases, the seizures can be triggered by activities that are harmless to others, such as watching television or playing video games, or by driving or riding during daylight along a road with spaced trees, thereby simulating the "flashing light" effect. Some people can suffer a seizure as a result of blinking one's own eyes. Contrary to popular belief, this form of epilepsy is relatively uncommon, accounting for just 3% of all cases. In all other epileptics, such lights are no more capable of triggering a seizure than in a non-epileptic person.
A routine part of the EEG test involves exposing the patient to flickering lights in order to attempt to induce a seizure, to determine if such lights may be triggering a seizure in the patient, and to be able to read the wavelengths when such a seizure occurs.
Head Injury 
A severe head injury, such as one suffered in a motor vehicle accident, fall, assault, or sports injury, can result in one or more seizures that can occur immediately after the fact or up to a significant amount of time later. This could be hours, days, or even years following the injury.
A brain injury can cause seizure(s) because of the unusual amount of energy that is discharged across of the brain when the injury occurs and thereafter. When there is damage to the temporal lobe of the brain, there is a disruption of the supply of oxygen.
The risk of seizure(s) from a closed head injury is about 15%. In some cases, a patient who has suffered a head injury is given anticonvulsants, even if no seizures have occurred, as a precaution to prevent them in the future.
Menstrual Cycle 
See "Catamenial" Epilepsy
Other medications 
- Tricyclic antidepressant
- The following antibiotics: Isoniazid, Lindane, Metronidazole, Nalidixic acid, and Penicillin, though Vitamin B6 taken along with them may prevent seizures
- Vitamin B1 deficiency (Thiamine deficiency) was reported to cause seizures, especially in alcoholics 
- Vitamin B12 depletion (Pyridoxine deficiency) was reported to be associated with pyridoxine-dependent seizures.
- Folic acid in large amounts was considered that might counteract the antiseizure effects of antiepileptic drugs and increase the seizure frequency in some children, although that concern is no longer held by epileptologists.
Sudden withdrawal from anticonvulsants may lead to seizures. It is for this reason that if a patient's medication is changed, the patient will be weaned from the medication being discontinued following the start of a new medication.
If treated with the wrong kind medication antiepileptic drugs (AED), seizures may increase, as most AEDs are developed to treat a particular type of seizure.
Missed dose 
A missed dose or incorrectly timed dose of an anticonvulsant may be responsible for a breakthrough seizure, even if the patient has often missed doses in the past, and has not suffered a seizure as a result of the missed dose. Missed doses are one of the most common reasons for a breakthrough seizure. Even a single missed dose is capable of triggering a seizure in some patients. This is true, even when the patient has not suffered a seizure after previously missing much more of his/her medication. Doubling the next dose does not necessarily help.
Missed doses can occur as a result of the patient's forgetfulness, unplanned lack of access to the medication, difficulty in affording the medication, or self-rationing of the medication when one's supply is low, among other causes.
Sleep deprivation 
Sleep deprivation is the second most common trigger of seizures. In some cases, it has been responsible for the only seizure a person ever suffers. However, the reason for which sleep deprivation can trigger a seizure is unknown. One possible thought is that the amount of sleep one gets affects the amount of electrical activity in one's brain.
Patients who are scheduled for an EEG test are asked to deprive themselves of some sleep the night before in order to be able to determine if sleep deprivation may be responsible for seizures.
In some cases, patients with epilepsy are advised to sleep 6-7 consecutive hours as opposed to broken-up sleep (e.g. 6 hours at night and a 2-hour nap) and to avoid caffeine and sleeping pills in order to prevent seizures.
In one study, emotional stress was reported by 30-60% prior to their seizures, thereby being the leading cause. This may include stress over hard work one is trying to accomplish, one's obligations in life, worries, emotional problems, frustration, anger, anxiety, or many other problems.
Stress may trigger a seizure because it affects the hormone cortisol. Stress can also affect the part of the brain that regulates emotion. Although stress can alter levels of these hormones, it remains unclear whether or not stress can directly result in an increase in seizure frequency.
See also 
- 100 Questions & Answers About Epilepsy, Anuradha Singh, page 79
- Keyser A, De Bruijn SF. Epileptic manifestations and vitamin B1 deficiency. Eur Neurol. 1991;31(3):121-5. http://www.ncbi.nlm.nih.gov/pubmed/2044623
- Fattal-Valevski A, Bloch-Mimouni A, Kivity S, Heyman E, Brezner A, Strausberg R, Inbar D, Kramer U, Goldberg-Stern H. Epilepsy in children with infantile thiamine deficiency. Neurology. 2009 Sep 15;73(11):828-33. Epub 2009 Jul 1. http://www.ncbi.nlm.nih.gov/pubmed/19571254
- Vitamin B-6 Dependency Syndromes ; Author: Anjali Parish, MD; Chief Editor: Jatinder Bhatia, MBBS. http://emedicine.medscape.com/article/985667-overview
- Folic Acid and Epilepsy, Martha J. Morrell, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC320966/