Best Answer: This may be an allergic reaction to bananas. There is a protein in bananas called chitinase that can cause an allergy reaction, which can include stomachaches and stomach pain. Chitinase is also found in avocados and kiwifruit. Banana intolerance can also be caused by something called vaso-active amines. These are histamines-like chemicals that can mimic an allergic reaction. The vasoactive amine in bananas is serotonin, and this can cause abdominal cramping.