What are the most common symptoms of lactose intolerance?

GI problems: Lactose intolerance is the inability to digest lactose due to a deficiency in the enzyme lactase. Common symptoms of this condition include abdominal bloating, abdominal cramps, diarrhea, gas, and nausea. These symptoms tend to occur soon after the ingestion of milk products. Infants or children with lactose intolerance may have slow growth or weight loss.