Reaction n. -A response to a stimulus.  A reverse or opposing action. (The Free Dictionary)

IC Reaction n. A painful response to food, water, chemicals, herbs, smells, stress, drink, sexual intimacy, hair/face/body products, medication, cleaning supplies.  The list for IC Reaction is not inclusive and can vary by person to person and from moment to moment.  (Carin Willis, IC Patient Definition)

It can be difficult having IC no matter if your case is mild, moderate or severe because of all of the aspects of our bodies and lives the disease touches.  I sometimes hate having to defend my choice to eat certain foods, abstain from using swimming pools and hot tubs and using certain body products for fear of it causing a painful reaction.  People can usually grasp the concept of a painful bladder disease but it is usually more difficult to understand the allergies to food, drink, chemicals, etc., or that by ingesting any of the aforementioned items might cause a horrific flare-up of pain. 

I personally still have the occasional reaction (some IC patients call them flare-ups) to foods that other people might prepare or by trying out a new shampoo that is touted as being free of chemicals and made for "sensitive people".  It is a frustrating part about living with IC.  The one thing I have learned to control is my reaction to a reaction.  Instead of flooding my body with more panic and fear, I try to calm my fears and remind myself the painful reaction will pass away in 24 hours or less.  I drink extra water to try and flush the reactionary items out of my body.  It's the little things that can make a huge difference when dealing with IC and all of its machinations of pain and confusion.