People who are lactose intolerant do not produce the enzyme lactase are therefore cannot digest the sugar lactose (a disaccharide composed of a molecule of galactose and glucose). If they ingest lactose, they typically can get cramps or gas. This is NOT an allergy, so they wouldn’t have a life-threatening anaphylactic reaction.
Our products that contain whey isolates (most of the drinks) only contain about 0.05% lactose and this small amount usually does not cause any problems with these folks. I would have them avoid the products that contain whole milk protein (the cappuccino, the chocolate drink, the omelet, the crispy cereal, puddings, etc). The other option is to let them try a “small amount” of some of these foods and to see if they in fact do experience any discomfort. They can take one of the many products for lactose intolerant people that contain lactase (i.e“Dairy-Eze” or “Lactaid”). But most of these folks just opt to avoid the foods containing the whole milk protein.