Pineapple is one of the most pungent fruits to snack on. Sure, lemons probably have them beat in the bitter and tart categories, but pineapples are the cause of sore tongues and lips everywhere.
The irritation is caused by a combination of enzymes in pineapples called bromelian, which break down proteins and essentially attack your tongue, cheeks, and lips on contact. But once you chew and swallow it, both your saliva and stomach acids overtake them. So if your mouth hurts after eating raw pineapple, you’re not alone—it happens to virtually everyone. The good news is that your tongue rebuilds those proteins and amino acids, so it won’t be sore for long.