People creeped out after realising why some pupils go red

 Taking a group photo in a dark environment can be ruined by the flash turning everybody's eyes red, but people are only just realising why it happens - and it's pretty gross.

There's a reason your eyes turn red when you take a photo with the flash on - and it's actually pretty gross.

If you've ever taken a group photo in an environment with low lighting, you'll probably know how easily the image can be ruined by the need to put the flash on, as it can make some people's pupils turn red, which often looks creepy. But it turns out that there's a very specific reason why your pupils turn red in photos, and some people are only just realizing what it is. What's more, it's left some so freaked out that they've vowed never to use the flash again.

The reason behind your red pupils was uncovered in a TikTok video by Nicholas Grant, who posted a clip to his @nicholas_grant_ account explaining the interesting science behind the phenomenon. He said: "You've probably heard that red eye in photos is caused by the flash reflecting back to the camera, but it turns out what actually happens is a little more interesting.

"If you're in a dark room, your pupil opens up really wide to let in the light and it's in this situation that you would use a flash. Normally, if your eye sees a bright light, it closes up. But a flash is too fast for the pupil to react. It's the pupil being open that causes the red eye. That's why some cameras do a double flash - one to close the pupil and one to actually take the photo.

Now that we understand what causes our pupils to go red, we can tackle the most important question - why red? Well, this is what has left people grossed out, as Nicholas explained that the red tone is caused by the blood vessels in your eyes. He added: "It turns out that the colour you see is actually the flash lighting up the inside of your eyes and it gets the red look because of the blood vessels in your eyes."

But according to the American Academy of Ophthalmology, seeing red when you take a picture with the flash on is actually a good thing - because it means your eyes are healthy.

They stated: "A red reflex happens when the flash of a camera lights up the blood-rich retina. If the eyes are looking directly at the camera lens and the colour of the reflex in both eyes is red, that's usually a good sign that the retinas of both eyes are unobstructed and healthy."

Even with the knowledge that it's a good sign, however, some commenters on Nicholas' video were still creeped out. One person asked: "So that's literally us seeing the inside of our eyes?!," while another added: "That is a bit creepy not going to lie." A third also posted: "That's scary as f**k!"