Why do bananas

Same thing happens to me, and they never bothered me until about a year or two ago.  I have no idea why.

I can only eat bananas when they're still green.  Once the skin get soft, or a lot brown starts to appear, I cant eat them either. 

The only way I eat them now, is in a smoothie.  Longer shelf life of the banana but they still have to have very little in terms of brown spots on the skin.  But I mix a banana, mixed fruit, peanut butter, yogurt, OJ and skim milk every morning before my run with no adverse effects.  I actually feel worse when I dont have it, or something in my stomach before I work out in the morning. 

 I also can only eat bananas when they're under-ripe. (Though I don't eat them totally green-- just green-ish.)  If I eat them ripe or over-ripe, they're not only too sweet for my taste, but I get itchiness in my throat and ears as with my nut allergies.  I've developed the wacky idea that it has something to do with the little black seeds in the banana which grow more evident when it is ripe but I have no real evidence to back up this and I'm pretty sure it is completely false.

Eating them with/in something, however, causes no problems, regardless of ripeness.  I also get the same kind of response from some apples and pears. 

Anyhow, in regards to the OP and others who experience actual abdominal pain and even vomiting, it is definitely an allergic reaction.   From my understanding, the allergens in banana are similar to those in natural latex and, when you eat a banana, you have an allergic reaction in your tummy.   Are any of the above posters allergic to latex?  Or also have reactions to kiwi, mango, chestnut, or avocado?  Apparently, those also contain the same allergen protein.

Also, I don't think that it is linked to Potassium unless you're already taking mega-doses of Potassium supplements which is very unlikely.  And I'm sure everyone here already knows Potassium is vital to cramp prevention and that the body does not store it so you must get a regular intake of it.  Have no fear though-- potatoes with the skin on pack an even better Potassium punch!  Not as practical and munching on a banana on the way to a work out.  But I'm sure anyone can fit in a quick baked potato.

Hmm I am able to eat the foods mentioned without problem, and as far as I know I am not allergic to latex, used latex gloves a bit when I worked.

I heard you the first time..... J/K

Wow, other than you my wife is the only person I have ever heard metion "The Brat Diet."

Whoa, no idea how I missed that.  I agree completely that that is NOT an allergic reaction.