Allergic responses are pretty quick - usually within a couple of hours. Food intolerance can take up to 2 days to manifest. As for reflux, it's probably more physiological, or structural as Bruce says. If you have other symptoms that point to food allergy or food intolerance (a rash that comes and goes, itching, wheezing, or other unexplained gut symptoms like bloating or cramping), then it may be worth keeping a food and symptom diary. It may be worth doing anyway, just to prove that the reflux or GERD is working in its own little life cycle, regardless of the type of food eaten. If you do happen to have some hidden triggers, then that would also help to pin them down. You should keep the diary for a couple of weeks and also give yourself a grading for your symptoms (like a mark out of 10 for the day, 10 being the worst possible you could be and 0 being totally symptom free). You can keep a note of other things that may be triggers - exercise, stress, lots of bending and picking things up (which you do all day if you're a mummy!!).
New stuff: GERD. Interstitial Cystitis
Lifelong stuff: Food allergies, eczema, asthma