All the immunologists and medical literature I've seen say there is a difference, and that only true allergy causes an immune response that can be corroborated by blood or skin prick tests. Whereas food intolerance is supposedly limited to a gastrointestinal response, but I wonder given my experience and the one @jenlemon describes if science just hasn't progressed enough to prove that food intolerance could very well involve the immune system, but without the anaphylaxis, wheezing, mouth swelling, hives, and other classical immunological symptoms. The advice I've been given is always to avoid the offending food or put up with the consequences, which are intolerable and disabling. And what can you do when you react to all or nearly all food? I also wonder if celiac disease, even on a gluten-free diet, could predispose someone to have systemic reactions to lots of other foods. I wish someone would do a research study.