Symptoms that may indicate you have a food sensitivity include:
joint pain/swelling, migraines, irritable bowel disease and other colon diseases, eczema/psoriasis, autoimmune disease, fibromyalgia, arthritis, and the inability to lose weight.
Food sensitivities are most difficult to identify because symptoms can develop up to 72 hours after eating an offending food unlike true food allergies which typically have immediate symptoms. 
To test for delayed food sensitivities, we use panels that involve a blood draw and can test for up to 200 different foods, food additives and colors. Once offending foods have been identified, steps are taken to heal the gastrointestinal tract using special probioitcs and supplements.
Our patients have been astonished which foods are actually triggers and how avoiding these foods results in resolution of their symptoms.