It seems like tight clothing is likely to put mechanical pressure against your gut and depending on the sensitivity of your enteric nervous at any given time (based on current inflammation and functional status for instance), it could activate different enteric nervous system neurons. Hyperactivation of the enteric nervous system could lead to increase in firing and inflammation at the level of the gut which could trigger the brain-gut axis activating a cascade of the immune, endocrine and neuronal pathways that lead to a flare. It seems to me, based on my personal experience, experiences of others and my knowledge of the human body and brain that anything that hyperactivates/sensitizes the neurons in the enteric nervous could potentially lead to a flare. But the stimuli that could cause a flare would depend on the type of stimuli (anxiety/stress, physical pressure, molecules at the level of the gut lumen which can include inflammatory ones or food, but the list of potential stimuli goes on and on), intensity of the stimulus, the enteric nervous system's sensitivity to different stimuli (which can be changing frequently). Because our enteric nervous systems are unique to each of us (they have their own history of activity, exposures and functioning), I think that is why we can all have so many different symptoms, respond differently to stimuli and treatment and experience the symptoms differently. That is why most of us have developed various mechanisms to minimize our symptoms (some people avoid certain foods, some people avoid certain psychological stressors, some people avoid certain activities and any other combo of these) that are specific to our own systems responses. Sorry for the rambling response, I have just been thinking about the enteric nervous system a lot.