Sometimes when i eat citrus fruits my tongue feels like it is swollen. what causes this? this is especially true when i eat pineapple.

Very : Very likely an "oral" allergy syndrome. Would see an allergist re this. There is usuaaly a relationship with inhalant-pollen allergies.

Was it not ripe?: If the pineapple wasn't ripe enough, the tongue can be affected by too much acidity. All citrus should be eaten ripe in order to make sure the acid (needed to produce/develop the fruit) is at low levels. Pineapple has bromelain, an enzyme that is very good at breaking down protein. In a cookbook, it is suggested as a marinade, but too long & it will make the meat mushy. Can happen to mouths!