Questioned on why Huw Edwards and Fiona Bruce spend so much energy anticipating flash-bulbs, the BBC seemed oddly reluctant to answer, but referred me to Ofcom, who revealed the flash alerts are a regulatory requirement because of the risk to viewers with epilepsy. ... These are the parameters of television regulation.

Why do they give flash warning?

Scientists also know the characteristics of imagery that apparently triggers abnormal brain activity. Brightness appears to be the most intense trigger, followed by the rate at which an image flashes. Certain colors, like red, and patterns, like parallel lines and stripes, can induce seizures, too.

Should I put flash warning?

If you feel there's a good reason why your content should break the W3C guidelines, then we strongly urge you to give a warning before the flashing starts. For example, on a video, the warning should be before the user starts to play the video.