They’re a sweet treat, but before you reach for a bag, you might want to know something: Some gummy bears could send you rushing to the restroom.

Ingredients in sugar-free gummy bears have fueled scathing and embarrassingly funny online reviews, but if you’re the one caught feeling the side effects, the results are anything but amusing.

“It’s been 15 agonizing hours since the first gummy bear entered my body, and I’m typing this from a toilet,” reads one Amazon review for Haribo’s sugar-free gummy bears on Amazon.com.

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The reviews are written with flourish and range from the helpful to the way-too-graphic.

“Then came the, uh, flatulence. Heavens to Murgatroyd, the sounds…” reads another. “I couldn’t stand to stay in one room for fear of succumbing to my own odors.”

One reviewer titled their contribution: “Chemical weapons-grade gummy bears.” Another speculates: “Customers who bought this also bought: Pepto-Bismol, 4 pack of baby wipes, stomach pump, air freshener,” and more.

As humorous as these reviews might be, the potential side effects of these gummy bears are real, and here’s why.

Sugar Alcohols

Sugar alcohols are found naturally in certain fruits and vegetables, but they’re also often added to processed, sugar-free foods in place of sugar or other artificial sweeteners. While they, at 2 calories per gram, contain fewer calories than sugar, which has 4 calories per gram, they’re more calorie-heavy than artificial sweeteners like aspartame, which are calorie-free.

Because they don’t affect blood sugar levels as much as sugar, you’ll often find them included in foods marketed to people with diabetes. They’re found in candy, frozen foods and desserts, chewing gum, toothpaste, chocolate, and baked goods. In addition to sweetening foods, they’re used to add bulk and help foods stay moist.

But sugar alcohols have one major caveat, as the gummy bear reviews reveal.

Sugar Alcohols, Diarrhea, and Flatulence

In the case of Haribo’s sugarless gummies, the sugar alcohol culprit is maltitol, which is found in the ingredient lycasin.

But this isn’t the only sugar alcohol that could lead to unpleasant digestive symptoms. A position paper in the Journal of the Academy of Nutrition and Dietetics affirms that consuming more than 30 grams of any sugar alcohols like lacticol, isomalt, or xylitol can have similar effects.

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From the Amazon reviews of these particular gummy bears, it would seem that some people are more sensitive than others to these effects. But if you’re among those unfortunate enough to have a reaction, you could experience increased flatulence, watery stools, bowel movement frequency, and borborygmus, or rumbling and gurgling noises from your intestines. It can be more serious or uncomfortable for those with bowel diseases such as irritable bowel syndrome.

Keep an Eye Out

Fortunately, avoiding the effects of sugarless gummy bears may not be so difficult, since the Amazon-reviewed culprits are no longer available. But if you want to avoid taking them in via other foods, look no further than nutritional labels.

Polyols is another name for sugar alcohols. You may also see them listed as:

Be wary of foods that are labeled sugar-free, and investigate what ingredients are used to sweeten them. While you’ll most often find sugar alcohols in baked goods, candies, and chewing gum, you can also find them in health-related products like low-carb sports bars, mouthwash, toothpaste, vitamins, and even some medicines.