Inability to fully digest lactose, the sugar in milk and dairy products, due to deficiency of lactase enzyme in the small intestine. Very common worldwide, especially in certain ethnic groups. Not dangerous but can cause uncomfortable symptoms.

• 1Lactose tolerance test
• 2Hydrogen breath test
• 3Stool acidity test (children)
• 4Genetic testing
• 5Trial of lactose-free diet
• 6Elimination diet

Excellent. Not dangerous, just uncomfortable. Easily managed with dietary modifications. No impact on life expectancy. Most can tolerate some lactose.

• No primary prevention (genetic)
• Early recognition
• Dietary education
• Lactase enzyme use
• Lactose-free alternatives