Last week, fans of the new Oreo Peeps discovered that eating a lot of the cookies—a vanilla shell with bright-pink filling—left them with an unexpected surprise in the toilet: pink poops. People can’t stop voicing their alarm, concern, and amusement on Twitter, Buzzfeed reports.

This isn't the first time people have taken their poo problems to Twitter. Back in 2015, Burger King's Halloween-themed Whopper with a black bun came back to haunt diners in the form of neon-green doo. But it actually isn't unusual to have brightly colored bowel movements, according to Jamile Wakim-Fleming, MD, a gastroenterologist at Cleveland Clinic. Lots of other foods can have the same effect.

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“Normal stool is light to dark brown in color,” Dr. Wakim-Fleming says says. “The bile secreted into the intestines turns digested substances brown. When we see different colors, it’s typically because of dyes and additives that are not digested.” In the case of Oreo Peeps, it's a food dye called FD&C Red Number 3.

You might find your poop changes color after consuming a lot of these foods:

Beets (red)

Tomato skin (red)

Tomato juice/soup (red)

Licorice (black)

Leafy greens or green juices (green)

Popsicles (any color)

Kool-Aid (any color)

Jell-O (any color)

Carrots (orange)

Sweet potatoes (orange)

Apricots (orange)

Icing (any color)

Gum or hard candy (any color)

Medicines can also affect your the color of your waste. Iron tablets and Pepto-Bismol act in your digestive system, and can turn stools black, for example. Dr. Wakim-Fleming says green, red, or white capsules can also turn up in your toilet.

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Most colors are generally harmless, but Dr. Wakim-Fleming says she will always ask questions in the presence of a new poo hue. “First, I’ll check diet,” she says. “If someone says they’ve been eating green Jell-O and have green stools, then we’ve usually figured it out. But I’ll also check and make sure there are no other symptoms, like fever, diarrhea, or weight loss.”

If the stool is very light tan, then there’s a reason for concern. “Since bile turns the stool brown, a tan color means the bile didn’t get into the intestine,” Dr. Wakim-Fleming explains. “There could be an obstruction in the bile duct, a stone or tumor in the pancreas or the liver. Hepatitis can also turn the stool tan and the urine dark in color.”

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When red or black stool is accompanied by changes in consistency, Dr. Wakim-Fleming says it's usually caused by blood. “If the stool is black and tarry, then there’s typically blood from the upper GI; this could be from an ulcer or NSAID use, or varicose veins in the stomach or esophagus," she says. "If the stool is maroon, there’s typically blood lower in the GI tract, and we’ll check for things like inflammatory bowel disease and Crohn’s disease.”

Bright red blood is typically a bleeding issue in the colon, like hemorrhoids. If you suspect you have blood in your stool, then call your doctor ASAP. If you’re ever in doubt, err on the side of caution and get it checked out.

This article originally appeared on Health.com.