I believe it was Dr. David William's newsletter where he said years ago that he always travels with cilantro extract and puts a few drops in a glass of water to purify it, and the label says 10 to 15 drops in warm water for indigestion type problems.  I've quieted many rumblings after getting what I think was salmonella...it works for me, and I keep it on hand all of the time.  My family uses it too.  I remember Dr. Williams commenting that he figured out why the Mexican people eat a lot of cilantro in their meals.  
Another reason I originally bought it was that I read that it was good at removing aluminum and other heavy metals.  I am alergic to aluminum and costume jewelry...which I think has a lot of nickel.  I've since learned that if the cilantro extract is used as a detox you should also take chlorella with it to help carry the metals out of the body.  This has to do with cilantro being able to get through the blood/brain barrier, and you don't want the metal going into the brain.  
For an occasional stomach ache I don't worry about chlorella, although I keep it on hand.  But I would be wrong not to advise you to use it, especially if cilantro is taken on a regular basis.
https://www.health-marketplace.com/Cilantro.htm    This is what I use.