Summary
Lactase deficiency occurs when the body produces too little lactase, the enzyme needed to digest lactose (a sugar found in milk and dairy products). There are four types of lactase deficiency:
- Primary (most common) – A gradual decrease in lactase levels after early childhood.
- Secondary – Caused by an illness or injury affecting the small intestine.
- Congenital (very rare) – A condition present from birth, where the body cannot produce lactase.
- Developmental – Seen in premature infants whose intestines are not fully developed.
Lactose intolerance occurs when lactase deficiency leads to digestive discomfort after consuming dairy products. Symptoms include diarrhea, bloating, stomach pain, and, in some cases, headaches, fatigue, joint pain, or skin issues.
Diagnosis and When to Seek Help
If your child experiences stomach discomfort, diarrhea, or bloating after consuming dairy, consult a doctor.
Between 5% and 15% of infants show signs of an adverse reaction to cow’s milk protein, which may be confused with lactose intolerance. However, this condition typically resolves by age 4-5 years and differs from the rare congenital lactase deficiency, which causes severe diarrhea from the first days of life.
To determine the cause of symptoms, doctors may recommend:
- Prick tests and IgE antibody tests – These help diagnose cow’s milk protein allergy.
- Dietary elimination and challenge – Temporarily removing dairy from the diet and reintroducing it to see if symptoms return.
- Lactose breath test – Measures hydrogen levels in the breath after consuming lactose.
- Stool acidity test – Used in infants to check for lactose malabsorption.
In most cases, tests for lactase deficiency will be negative in children with a cow’s milk protein allergy.
Management
Treatment depends on the type and severity of lactase deficiency. Options include:
- Reducing or eliminating lactose – Many children and adults can tolerate small amounts of lactose, while others need to avoid it completely.
- Lactose-free alternatives – Including lactose-free milk, dairy substitutes, and lactase enzyme supplements.
- Ensuring adequate calcium intake – If dairy is removed from the diet, it’s important to include other calcium-rich foods like leafy greens, fortified plant-based milk, nuts, and fish with edible bones.
Follow-Up and Monitoring
Children with lactose intolerance should have regular follow-ups to ensure they are getting enough nutrition, especially calcium and vitamin D. If symptoms persist or worsen, further evaluation may be needed to rule out other digestive conditions.
Most children with secondary lactase deficiency recover once the underlying cause (such as an infection) resolves, while those with primary lactase deficiency may need lifelong dietary adjustments.
If you suspect your child has lactose intolerance or lactase deficiency, speak to a healthcare provider to determine the best approach for management.
History and Exam
Key diagnostic factor
- presence of risk factors
- history of irritable bowel syndrome diagnosis
- symptoms after ingestion of dairy products
- diarrhoea
Other diagnostic factors
- abdominal pain/discomfort
- borborygmi
- flatulence
- skin rashes
Risk factor
- black, Native American, Asian, Hispanic, or Jewish ethnicity
- adolescence and early adulthood
- family history of lactase deficiency
- enteritis/gastroenteritis
Diagnostic Investigations
1st investigations to order
- trial of dietary lactose elimination
- FBC
Investigations to consider
- lactose hydrogen breath test
- stool culture
- faecal pH
- faecal reducing substance/sugar
Emerging tests
- genotyping
- 13C-labelled lactose breath test
Book an Appointment
Other Related Conditions
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