Irritable bowel syndrome or IBS is an example of a food intolerance.
Symptoms include such things as abdominal pain, bloating, heartburn, headaches, fatigue, etc.
As with all food intolerances, symptoms vary and depend on the amount of food consumed, the timing of the meal and on the other meals consumed that day. They all accumulate together to potentially knock the sufferer over the tolerance levels their bodies can cope with.
It is important to seek medical advice on IBS as sufferers of Coeliac Disease display similar symptoms and can often go mis-diagnosed for years.
Diets such as gluten-free and the Low-FODMAP diet are often recommended to IBS sufferers, as are probiotics, probiotics, exercise, etc. Medication can not treat IBS as a whole but can help to relieve individual symptoms when necessary.