You might want to look into something called Eosinophilic Gastroenteritis. My DH has this and it causes lots of food allergies and stomach pain. Allergy tests don't always identify the offending food(s) that may trigger the disease/symptoms, unfortunately.
for more info.
Chronic Lyme, Bart., Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut dysmotility & non-specific inflammation, Lupus, Osteoporosis, etc.; G-Tube
Meds: Flagyl, Domperidone, Claritin, Singulair, Andrographis & other herbs, homeopathy, supplements, etc.