鳳梨與芋頭都含草酸鈣 (calcium oxalate)，草酸鈣會形成草酸鈣晶針 (raphides)。削好的鳳梨碰水，草酸鈣晶針容易游離出來，會刺激口腔，所以不能再用水沖洗。徒手削芋頭沾到黏液後用冷水洗手，越洗越刺癢，應該也是這個緣故。
有人說鳳梨咬舌刺口是果實含「鳳梨酵素」，會分解舌頭肌肉蛋白，引起口舌刺痛。是嗎？
以下這段英文網站的文字就是這種以訛傳訛的代表 (incorrect, but often cited, interpretation)：
That when you eat pineapple, it's actually eating you back - pineapple's bromelain enzyme digests proteins, which is the reason for that tingly feeling on your tongue when you eat it. blogs.unimelb.edu.au/scienc...
木瓜也含「木瓜酵素」(papain)，也會分解蛋白質，怎麼就不咬舌刺口呢？
研究指出，真正的禍首可能是削好的鳳梨沾到水，果實中的草酸鈣結成晶針 (raphides)，刮刺舌頭及口腔，造成不適感。(raphides, needle-shaped crystals of calcium oxalate that occur in pineapple fruits and leaves, likely cause microabrasions (刮刺), contributing to mouth discomfort.)
十幾年前果販削好鳳梨後會用冷水沖洗，現在賣鳳梨現削都不碰水，也是這個原因。
Along with papain (木瓜酵素), bromelain (鳳梨酵素) is one of the most popular proteases (蛋白酶) to use for meat tenderizing. 香港人烹調肉類要讓肉吃起來更嫩，往往加嫩肉精去醃過，嫩肉精的主要成分就是木瓜酵 或鳳梨酵素。 (Jerome Su, August 5, 2019)