5yo Has Had Allergy IGG Blood Testing Done All Neg

5yo has had allergy IGG blood testing done all neg results and scratch testing done all neg. she has persistent post nasal drip and barking cough, does have now freq ear infections or fluid in ears. Allergist feels is reflux, she has no c/o heartburn, or difficulty eating or swallowing. was told now to cut out all dairy and chocolate for 2 wks. is this accurate? and what other things should i watch for or expect?