If too much pineapple makes you want to scratch your mouth, you're not alone.
A 2019 article in the Annals of Allergy, Asthma and Immunology suggests the cause is an enzyme complex called bromelain.
"At the present, there isn't much information concerning bromelain's palatability," said Alessandro Colletti, a pharmacologist at the University of Turin in Italy.
After eating several pineapple chunks, you may feel the bromelain breaking down mucin proteins in your mouth's protective mucosal layer.
Your mouth rapidly replaces bromelain-damaged cells to avoid chronic harm from pineapple proteases.