I have been diagnosed as LI but my symptoms also go way beyond the symptoms usually attributed to LI. I don't get headaches or vomit but I do suffer from the latter two that you mention. The diarrhea comes within 6 hours and the lethargy and feeling unwell come in 36 hours or so. The reason why Lactaid pills don't work is that they deal with the LI symptoms exclusively. I think you should consider that your daughter has a dairy allergy and react accordingly. There might be other reasons, but if total elimination of dairy works, then go for it. That is what I did and it has worked for me. By the way, some LI symptoms are quite close to Irritable Bowel Syndrome and Doctors may diagnose a problem as that. Don My question; My >daughter's symptoms do not seem to be at all typical for LI, although the >onset does appear to be initiated by ingestion of milk products. Her >symptoms include headache, vomiting, lethargy and diarrhea. She becomes >very pale, and her headaches are similar to migranes (i.e. sensitive to >light, etc)