If you’ve ever seen a block of cheddar that’s started to develop a pinkish hue, you may suspect that chemical additives are to blame. While the ingredient responsible is indeed an additive, it’s also a fairly innocuous one that cheesemakers first started using centuries ago.

Cheese is often associated with a bright orange color, but in most cases it doesn’t develop that shade on its own. Before dyeing cheese became a common practice, the rich golden color occurred naturally in cheese made from milk from cows with beta-carotene-rich diets. Then, in the 17th century, some English cheesemakers discovered that they could squeeze more profits from their milk by skimming the cream off the top to make into butter or to sell on its own. The problem was that the cream contained most of the orange pigment, so by removing it, that sought-after coloring was lost. Cheesemakers found a way around this by adding coloring to their low-fat cheeses. One popular dye they used was annatto, an additive derived from the seed of a tropical plant that’s still used in cheese today.

While the additive itself has been used for hundreds of years, the issue of pink discoloration is a fairly new one. Most cheese that’s sold today sits baking under the fluorescent lights of a grocery store display case for hours at a time. This light bleaches out the annatto’s yellow component, which leaves it with an unappetizing pink tinge. Oxidation has similar pinking effects, which is why you may have noticed your cheddar turning pink after sitting open in your fridge for too long. If the unintended color creeps you out, consider switching over to a white cheese.

[h/t Gizmodo]