The reason why pineapple makes your mouth feel numb is because it contains enzymes that break down proteins as well as it being acidic. The enzymes in pineapple are often used in meat tenderizers. However, I wouldn't let this deter you from pineapple, the enzymes will not tenderize your tongue (unless you eat it constantly!
) and it contains good fibre and lots of great nutrients like antioxidants (vitamin C/A).
Enjoy the pineapple!