If you’ve ever accidentally taken a big swig of orange juice immediately after brushing your teeth, you know it’s quite the unpleasant taste. But have you ever wondered why these two things make for such a horrible combination?

Turns out, there’s a pretty basic scientific reason: the presence of sodium laurel sulfate in toothpaste.

Sodium laurel sulfate (SLS) is a surfactant, or type of soap. In addition to toothpaste, it’s also commonly found in a variety of household products, including bubble bath, lip balm and shaving cream. SLS is what creates the foam while you brush.

Two-pronged attack

SLS works to ruin your glass of OJ in two ways: first, it suppresses the “sweet” receptors on the taste buds, making you temporarily unable to taste any sweet flavors, not just OJ.

Toothpaste with SLS makes it so you can’t taste sweetness and you can’t block bitterness.

Second, it breaks up phospholipids, which are the agents that block the “bitter” receptors on your tongue. Orange and other citrus juices are usually comprised of a mix of sweet and bitter flavors, so the introduction of toothpaste with SLS to your mouth means that you now can’t taste the sweetness and can’t block the bitterness, leaving you with that unfortunate, gross taste in your mouth. 

If you can’t imagine starting your morning without a glass of OJ, there are a few things you can do to avoid that dreaded taste. You can try switching to a toothpaste that doesn’t contain SLS, or you can start brushing your teeth after breakfast. If you choose the latter, be sure to wait 30 minutes after having citrus before brushing to avoid damaging the enamel on your teeth.

And remember — it never hurts to brush up on your dental hygiene in general!