Overview
Definition:
Lactose intolerance is a digestive disorder characterized by the inability to fully digest lactose, a sugar found in milk and dairy products
This is due to insufficient production of the enzyme lactase
Milk protein allergy (MPA), specifically Cow's Milk Allergy (CMA), is an immune system reaction to proteins found in milk, such as casein and whey
It is an adverse immunological response, not a digestive enzyme deficiency.
Epidemiology:
Lactose intolerance is highly prevalent worldwide, affecting an estimated 65-70% of the global population, with significant geographic variations
It is less common in infants and increases with age
CMA is one of the most common food allergies in infants and young children, affecting approximately 2-3% of infants
Most children outgrow CMA by school age.
Clinical Significance:
Differentiating between lactose intolerance and MPA is crucial in pediatric practice
Misdiagnosis can lead to unnecessary dietary restrictions, impacting growth and development, or failure to identify a potentially serious allergic reaction
Accurate diagnosis guides appropriate management, ensuring optimal nutrition and preventing adverse health outcomes for infants and children.
Clinical Presentation
Lactose Intolerance Symptoms:
Abdominal bloating
Abdominal pain or cramping
Diarrhea, often watery
Nausea
Flatulence
Borborygmi (rumbling stomach sounds)
Symptoms typically appear 30 minutes to 2 hours after consuming lactose-containing foods.
Milk Protein Allergy Symptoms:
Gastrointestinal: vomiting, diarrhea (sometimes bloody or with mucus), constipation, reflux, abdominal pain, poor weight gain
Skin: eczema, urticaria (hives), angioedema (swelling)
Respiratory: wheezing, cough, rhinitis, nasal congestion
Anaphylaxis: a severe, life-threatening reaction involving difficulty breathing, drop in blood pressure, and loss of consciousness
Symptoms can be immediate or delayed (hours to days).
Diagnostic Criteria:
There are no universally standardized diagnostic criteria for lactose intolerance, diagnosis is often based on clinical history and response to elimination and challenge
For CMA, diagnosis is typically based on a history consistent with allergy, elimination of milk protein, and reintroduction (oral food challenge), often guided by allergists
IgE-mediated CMA may also be supported by positive skin prick tests or specific IgE blood tests.
Diagnostic Approach
History Taking:
For suspected lactose intolerance: detailed dietary history, timing and nature of symptoms after dairy consumption, family history
For suspected CMA: detailed dietary history, timing of symptom onset relative to milk ingestion, specific symptoms (GI, skin, respiratory), presence of other allergies or atopic conditions, family history of allergies, and previous management attempts
Red flags for CMA include severe vomiting, bloody stools, poor growth, or signs suggestive of anaphylaxis.
Physical Examination:
For suspected lactose intolerance: focus on abdominal examination for distension, tenderness, and bowel sounds
For suspected CMA: thorough examination of skin for eczema or urticaria, auscultation of lungs for wheezing, and assessment of hydration and nutritional status
General well-being and growth parameters are critical in infants.
Investigations:
Lactose intolerance: Hydrogen breath test (measures hydrogen produced by gut bacteria fermenting undigested lactose), lactose tolerance test (measures blood glucose rise after lactose load, less commonly used), stool acidity test (in infants, indicates malabsorbed lactose)
CMA: Allergy testing (skin prick tests or specific IgE blood tests for IgE-mediated CMA), elimination diet followed by oral food challenge (gold standard for both IgE and non-IgE mediated CMA)
Stool examination for eosinophils or occult blood may be supportive for non-IgE mediated GI symptoms.
Differential Diagnosis:
Other causes of diarrhea and abdominal pain in infants: infectious gastroenteritis, other food intolerances (e.g., soy), celiac disease, inflammatory bowel disease (less common in infants)
Other causes of allergic reactions: other food allergies, medication reactions
Conditions mimicking CMA include GERD, cow's milk protein-induced enteropathy, and infective colitis.
Management
Lactose Intolerance Management:
Dietary modification: limiting or avoiding lactose-containing foods
Lactase enzyme supplements (taken with lactose-containing meals)
Calcium and Vitamin D supplementation if dairy intake is significantly reduced
Choosing lactose-free dairy products.
Milk Protein Allergy Management:
Strict avoidance of all milk proteins: this includes cow's milk, goat's milk, sheep's milk, and products containing milk derivatives
For infants, hydrolyzed formulas (extensively or partially hydrolyzed) or amino acid-based formulas are recommended depending on severity and type of CMA
Careful label reading for hidden milk ingredients
For breastfed infants, the mother should avoid dairy in her diet
Management of acute allergic reactions (e.g., anaphylaxis) with epinephrine.
Supportive Care:
Nutritional support is paramount in both conditions, especially in infants
Ensuring adequate intake of calcium, vitamin D, and calories for growth and development
Monitoring growth parameters (weight, height, head circumference) regularly
Education of parents/caregivers on dietary management, label reading, and recognition of symptoms
Allergy counseling for CMA, including emergency action plans.
Complications
Lactose Intolerance Complications:
Nutritional deficiencies (calcium, vitamin D) if dairy is completely eliminated without replacement
Dehydration from severe diarrhea
Poor growth (rare, usually due to concurrent issues or severe intolerance).
Milk Protein Allergy Complications:
Malnutrition and failure to thrive due to poor absorption or restricted diet
Eosinophilic esophagitis or gastroenteritis
Anaphylaxis (life-threatening)
Chronic eczema or asthma exacerbations
Developmental delays if nutritional needs are unmet.
Prevention Strategies:
For lactose intolerance: adequate calcium and vitamin D intake through fortified foods or supplements
For CMA: early recognition and prompt institution of an appropriate elimination diet
Education on cross-reactivity with other dairy sources
Maintaining a healthy gut microbiome may play a role in preventing excessive sensitization.
Prognosis
Factors Affecting Prognosis:
For lactose intolerance: severity of lactase deficiency, adherence to dietary modifications
For CMA: age of onset, severity of reaction, development of other atopic diseases, successful desensitization (in specific cases).
Outcomes:
Most individuals with lactose intolerance can manage their symptoms effectively with dietary adjustments
Many children with CMA outgrow their allergy by school age, but some may persist into adulthood
Prompt and appropriate management generally leads to good outcomes with resolution of symptoms and adequate growth.
Follow Up:
Regular follow-up with a pediatrician or gastroenterologist/allergist is recommended to monitor growth, nutritional status, and symptom control
For CMA, periodic re-evaluation for tolerance and potential oral food challenges are part of the long-term management strategy.
Key Points
Exam Focus:
The primary distinction: Lactose intolerance is a digestive enzyme deficiency (lactase), leading to maldigestion
Milk protein allergy is an immune response to milk proteins (casein, whey), leading to allergy
Symptoms of CMA can be much broader and more severe, including anaphylaxis.
Clinical Pearls:
Always consider CMA in infants with persistent GI symptoms like vomiting, diarrhea, blood in stool, or poor weight gain, especially if symptoms don't improve with lactose-free formula
Remember that CMA can be IgE-mediated (rapid onset) or non-IgE mediated (delayed onset), making diagnosis sometimes challenging
Oral food challenge is the gold standard for CMA diagnosis.
Common Mistakes:
Mistaking CMA for lactose intolerance and prescribing lactose-free formulas when the underlying issue is protein allergy
Incorrectly diagnosing lactose intolerance in infants who are actually experiencing CMA
Failing to recognize the signs of anaphylaxis in CMA patients
Inadequate nutritional assessment and management for infants with restricted diets.