Conditions that cause digestion or esophageal problems (nausea, cramping, heartburn)
A GM often not only serves as guide, and prompter, but often as host. Sometimes this may include providing food to players or taking breaks and allowing such things. If food is allowed at your table, be aware of the dietary restrictions of your player, as well as any concerns they may have with regard to other foods/smells that could trigger gag reflex. Once again this falls to communication in presession.
If there is a likelihood of esophageal distress that induces vomiting regardless of a control of environment, ensure that the necessary receptacles are available and at hand, or that access to facilities are clear and within reasonable traveling distance for the child.