Ah, the dreaded make-up flashback! Celebrities like Angelina Jolie, Nicole Kidman and Miley Cyrus aren’t immune to it, even with their hordes of make-up artists:

Here’s the science behind make-up flashback, and how to avoid it.

What causes make-up flashback?

The harsh white markings are caused by silica, an ingredient in many translucent powders, particularly those labelled as “HD”. (Note: silica is not the same as silicon and silicone!) The silica used in makeup is fumed silica, a type of amorphous silica which has been processed to give it a large surface area. This means that it’s great as a microscopic sponge for soaking up oil (kind of like activated charcoal but colourless).

It’s also fantastic for diffusing light – all the tiny surfaces scatter light at different angles, giving a blurry, matte texture, making your skin look flawless on HD video (hence the HD label).

But not when direct flash comes out!