What is the difference between lactose intolerance and Cow's Milk Protein Allergy (CMPA)?

Differences Between Lactose Intolerance and Cow's Milk Protein Allergy (CMPA)

Lactose intolerance and Cow's Milk Protein Allergy (CMPA) are fundamentally different conditions with distinct pathophysiological mechanisms, symptoms, onset patterns, and management approaches.

Pathophysiological Mechanisms

Lactose Intolerance

• Mechanism: Non-immunological digestive disorder caused by lactase deficiency
• Defect: Insufficient lactase enzyme to digest lactose (milk sugar)
• Types:
  • Primary: Age-related decline in lactase production (lactase non-persistence)
  • Secondary: Temporary reduction in lactase due to gut damage from conditions like viral gastroenteritis, giardiasis, celiac disease, or Crohn's disease 1
• Prevalence: Affects approximately 70% of the world's population 1

CMPA

• Mechanism: Immunological reaction to cow's milk proteins
• Types:
  • IgE-mediated: Immediate hypersensitivity reaction
  • Non-IgE-mediated: Delayed hypersensitivity reaction
  • Mixed: Combination of both mechanisms 2
• Proteins involved: Casein, β-lactoglobulin, α-lactalbumin, and other milk proteins

Clinical Presentation

Lactose Intolerance

• Symptoms: Primarily gastrointestinal
  • Abdominal pain
  • Bloating
  • Flatulence
  • Diarrhea
  • Borborygmi (stomach rumbling)
• Onset: Typically occurs after 5 years of age for primary lactose intolerance 1
• Severity: Dose-dependent; symptoms correlate with amount of lactose consumed

CMPA

• Symptoms: Multi-system involvement
  • IgE-mediated (immediate, within minutes to 2 hours):
    • Urticaria, angioedema, erythema
    • Vomiting, diarrhea
    • Wheezing, rhinitis, coughing
    • Hypotension (in severe cases)
  • Non-IgE-mediated (delayed, 2-72 hours):
    • Persistent diarrhea, vomiting
    • Blood in stool
    • Failure to thrive
    • Atopic dermatitis, eczema
    • Irritability, feeding difficulties 2
• Onset: Typically presents in infancy, often within first months of life
• Severity: Can range from mild to life-threatening (anaphylaxis)

Diagnostic Approach

Lactose Intolerance

• Clinical history: Symptoms related to dairy consumption
• Diagnostic tests:
  • Hydrogen breath test
  • Lactose tolerance test
  • Stool acidity test (in infants)
• Challenge: Lactose challenge to reproduce symptoms

CMPA

• Clinical history and physical examination: Detailed symptom documentation
• IgE-mediated CMPA:
  • Skin prick test
  • Serum-specific IgE testing 2
• Non-IgE-mediated CMPA:
  • Elimination diet as primary diagnostic tool
  • Atopy patch testing (not routinely recommended) 2
• Gold standard: Double-blind placebo-controlled food challenge (DBPCFC) 3
• Practical approach: Elimination diet for 2-4 weeks (IgE-mediated) or 2-6 weeks (non-IgE-mediated) followed by challenge 2

Management

Lactose Intolerance

• Dietary approach: Reduction but not complete elimination of lactose-containing foods 1
• Supplements: Lactase enzyme supplements
• Nutritional considerations: Ensure adequate calcium intake from other sources
• Duration: Lifelong for primary lactose intolerance; temporary for secondary forms

CMPA

• Breastfed infants:
  • Continue breastfeeding with maternal elimination diet
  • Calcium and vitamin D supplements for the mother 2
• Formula-fed infants:
  • First-line: Extensively hydrolyzed formula (eHF)
  • Second-line: Amino acid formula (AAF) for severe cases or if symptoms persist with eHF 2, 4
• Solid foods: Strict avoidance of cow's milk proteins
• Acute reactions:
  • Mild-moderate: Antihistamines
  • Severe: Epinephrine auto-injector 2
• Duration: Temporary - most children outgrow CMPA by age 5 3

Common Pitfalls

Lactose Intolerance

• Misdiagnosis: Often self-diagnosed without proper testing
• Overrestriction: Unnecessary complete dairy avoidance leading to nutritional deficiencies
• Confusion with CMPA: Particularly in young children where secondary lactose intolerance may occur due to gut damage from CMPA 1

CMPA

• Overdiagnosis: Attributing common infant symptoms to CMPA without proper testing
• Delayed diagnosis: Missing the diagnosis, leading to failure to thrive or malnutrition 3
• Inappropriate formula choice: Using partially hydrolyzed formulas that still contain allergenic epitopes
• Inadequate follow-up: Failing to reassess for development of tolerance 2

Key Distinctions to Remember

1. Pathophysiology: Enzyme deficiency (lactose intolerance) vs. immune reaction (CMPA)
2. Age of onset: Primary lactose intolerance rarely occurs before age 5, while CMPA typically presents in infancy 1
3. Symptom range: Primarily GI symptoms (lactose intolerance) vs. multi-system involvement (CMPA)
4. Management: Reduction of lactose (lactose intolerance) vs. strict elimination of cow's milk protein (CMPA)
5. Natural history: Typically lifelong for primary lactose intolerance vs. often transient for CMPA