People with lactose intolerance often feel nauseous and should avoid drinking milk. If they must drink milk, it needs to undergo special treatment first. Consuming untreated milk can lead to diarrhea in lactose-intolerant individuals, and severe cases may result in dehydration and electrolyte imbalance. Additionally, those with lactose intolerance should also check for any milk allergies or diarrhea caused by indigestion. It is essential to conduct allergen tests and, if necessary, take oral medication to regulate the digestive system.