Since you and your skin go way back, you probably have a pretty good idea of what it should and shouldn’t look like on a regular basis. It’s no wonder why you might be confused when melasma’s hallmark brown spots start to develop on different parts of your face.

Melasma is a harmless but potentially annoying condition that causes blotchy dark patches to show up on your skin.

Here’s what you need to know about melasma, plus how to lower the odds you’ll develop these spots at all.