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photosensitive epilepsy

Photosensitive epilepsy is when seizures are triggered by flashing lights or contrasting light and dark patterns. Photosensitive epilepsy is not common but it may be diagnosed when you have an EEG test. Flashing or patterned effects can make people with or without epilepsy feel disorientated, uncomfortable or unwell. This does not necessarily mean they have photosensitive epilepsy.

How common is photosensitive epilepsy?

Around 1 in 100 people has epilepsy and of these people, around 3% have photosensitive epilepsy. This is when seizures are triggered by certain rates of flashing lights or contrasting light and dark patterns. Photosensitive epilepsy is more common in children and young people (up to 5%) and is less commonly diagnosed after the age of 20.

How can I tell if I am photosensitive?

Many people know they are photosensitive if they have a seizure when exposed to flashing lights or patterns as a photosensitive trigger will usually cause a seizure straightaway. An electroencephalogram EEG carried out to help with diagnosis, may include testing for photosensitive epilepsy. This involves looking at a light which will flash at different speeds. If this causes any changes in brain activity, the technician can stop the test before a seizure develops.

What rate of flashing light can trigger seizures?


What patterns can trigger seizures?



How is photosensitive epilepsy treated?

Photosensitive epilepsy usually responds well to anti-epileptic drugs (AEDs) that treat generalised seizures (seizures that affect both sides of the brain at once).

Photosensitive factsheet

If seizures are triggered by flashing lights or certain patterns, this is called photosensitive epilepsy. Find out more with our photosensitive epilepsy factsheet. 

Managing photosensitive epilepsy

Possible triggers if you have photosensitive epilepsy



Factors that may increase the photosensitive risk





If suddenly exposed to a trigger


What may have a photosensitive trigger?

TV and computer screens that flicker


  • Faulty TVs or other screens that flicker.


  • A flashing image on a computer screen or game. 

Patterns in the natural environment

  • Sunlight through trees.

  • Sunlight through blinds.

  • Sunlight on water.


  • Rotating wind turbine blades, if certain weather conditions occur together with other specific factors.

Flashing or flickering lights or images


  • Strobe lights at performances or in nightclubs.

  • Lights flickering, such as faulty fluorescent tubes.

  • Fireworks, if they create a high enough flash rate.

  • Flashing bicycle lights or other LED lights, if this creates a high enough flash rate against a dark background, and the effect fills your vision. 

  • Several circuits of festive lights flashing together could increase the flash rate.

Reducing the risk of a photosensitive trigger

The environment and how you use a screen

  • Use a flatscreen TV or computer monitor.

  • Take regular breaks from the screen.

  • Sit well back from the screen.

  • Use a remote control to change channels.



  • Use the settings in Internet options to control moving images in your browser.




UK regulations


  • The Health and Safety Executive recommends that strobe lighting in clubs or at public performances, flashes at a maximum rate of four hertz (flashes per second) or less.

What is unlikely to be a photosensitive trigger?



  • Digital TV and plasma screens. Adjusting the brightness down on some screens can be helpful if you have photosensitive epilepsy.


  • Modern computer or TV screens have a very high flicker frequency. Flatscreen monitors, such as laptops, have a liquid crystal display ( LCD) that does not flicker, so are even less likely to trigger seizures.


  • ‘Real 3D’ cinema films Images are projected separately at each eye, reducing the already low intensity of the cinema screen even further and so there should be even less risk of seizures being triggered by ‘real 3D’ in cinemas.
