Any and every food is a trigger for someone with IBS. And a lot of other IBSers will eat whatever triggers you, personally, without any problem.With popcorn there is the fiber that can bother some people, starch that can bother some people, fat (if added) that can bother some people, and various other additive depending on the kind you go that can bother some people.So I'm sure it triggers someone, but it may be worth doing another trial with popcorn on another day when you have some time if you react to see if it was the food or it just happened to be an innocent bystander.Lots of NON-food things trigger IBS. It isn't always food.Things that may trigger your IBS that have NOT ONE THING to do with which food you ate (we all want it to be only food, but often we blame foods that are innocent).It is hot outsideIt is cold outsideThe inside temp is too different from the outside tempA storm front came throughYou didn't sleep well last nightYou have been exercising too muchYou have been exercising too littleYou have mental stressYou have emotional stressYou have stress about worrying if the popcorn will set off the IBS the next time you eat it.You have another health issues that is acting up.You have pain for any reason including an injury.People also can get conditioned response to food where your body will reject it just because something else made you sick the last time you ate it, so if anything consistently sets you off then good to avoid it.