What are the symptoms and management of cow milk protein allergy?

Cow's Milk Protein Allergy: Symptoms and Clinical Presentation

Cow's milk protein allergy presents with either rapid-onset IgE-mediated symptoms (hives, angioedema, wheezing, vomiting, anaphylaxis within minutes to 2 hours) or delayed non-IgE-mediated symptoms (chronic diarrhea, blood-streaked stools, failure to thrive, enteropathy), with the clinical presentation determining both diagnostic approach and management strategy. 1

IgE-Mediated Symptoms (Immediate Reactions)

Cutaneous manifestations are the most common presentation, occurring in 85.7% of IgE-mediated cases: 2

• Urticaria (hives) and angioedema are the hallmark symptoms 1, 2
• Symptoms develop within minutes to 2 hours after milk ingestion 1
• Flushing and pruritus may accompany skin findings 3

Gastrointestinal symptoms occur in approximately 40% of IgE-mediated cases: 2

• Acute vomiting (often projectile) 1, 2
• Abdominal pain and cramping 3
• Acute diarrhea 2

Respiratory manifestations include: 1

• Wheezing and bronchospasm 1
• Nasal congestion and rhinorrhea 3
• Throat tightness 1

Anaphylaxis represents the most severe presentation: 1

• Involves multiple organ systems simultaneously 1
• Asthma is a critical risk factor for severe reactions and fatal anaphylaxis in children with IgE-mediated cow's milk allergy 1
• Requires immediate epinephrine administration 1

Non-IgE-Mediated Symptoms (Delayed Reactions)

Gastrointestinal manifestations dominate non-IgE presentations, occurring in 38% of cases: 2

• Chronic diarrhea with or without blood 1, 3
• Blood-streaked or mucoid stools (allergic proctocolitis) 1
• Vomiting (less acute than IgE-mediated) 2
• Abdominal distension and discomfort 3

Growth and nutritional concerns: 1

• Failure to thrive and poor weight gain 1
• Protein-losing enteropathy with steatorrhea 1
• Weight loss in established cases 1

Cutaneous symptoms occur in approximately 50.6% of non-IgE cases: 2

• Atopic dermatitis/eczema (chronic presentation) 1
• Up to 37% of children under 5 with moderate-to-severe atopic dermatitis have IgE-mediated food allergy, but skin care should be optimized first before attributing symptoms to food allergy 1

Timing characteristics: 3

• Symptoms develop hours to days after exposure 3
• Onset typically occurs within the first year of life 1
• Median age of symptom onset is 6 weeks for non-IgE-mediated disease 2

Food Protein-Induced Enterocolitis Syndrome (FPIES)

FPIES represents a severe non-IgE-mediated subtype with distinct presentation: 4

Acute FPIES symptoms: 4

• Repetitive, projectile vomiting (typically 1-4 hours after ingestion) 4
• Profound lethargy and pallor 4
• Hypotension and shock in severe cases 4
• Hypothermia and metabolic acidosis 4
• Methemoglobinemia may occur 4

Chronic FPIES symptoms: 4

• Chronic, intermittent vomiting and diarrhea 4
• Failure to thrive 4
• Symptoms resolve within 3-10 days of switching to hypoallergenic formula 4

Severity classification for acute FPIES: 4

• Mild: 1-2 episodes of emesis, no lethargy 4
• Moderate: >3 episodes of emesis with mild lethargy 4
• Severe: >3 episodes of emesis with severe lethargy, hypotonia, ashen or cyanotic appearance 4

Symptoms in Exclusively Breastfed Infants

Cow's milk protein allergy can occur in exclusively breastfed infants through maternal dietary transfer: 5, 6

• Incidence rate of 0.5% in exclusively breastfed infants 6
• Symptoms include blood-streaked stools, eczema, and gastrointestinal distress 5
• Bovine proteins transfer into breast milk in sufficient quantities to cause allergic reactions 5, 6
• Improvement typically occurs within 1-2 weeks of maternal cow's milk elimination 5

Critical Diagnostic Distinctions

Cow's milk allergy must be distinguished from lactose intolerance: 7

• Lactose intolerance causes bloating, flatulence, abdominal pain, and diarrhea without immune involvement 7
• Lactose intolerance is rare in infants and young children compared to cow's milk allergy 7
• Cow's milk allergy is immune-mediated (IgE or non-IgE), while lactose intolerance is a metabolic enzyme deficiency 7

Age-Related Patterns

Timing of symptom onset: 2

• IgE-mediated: median age of onset is 10 weeks 2
• Non-IgE-mediated: median age of onset is 6 weeks 2
• Interval between cow's milk introduction and symptom onset: 4-5 days 2

Natural history and prognosis: 1, 8

• Most children develop tolerance by 2-3 years for non-IgE-mediated disease 1
• Majority regain tolerance within the first 5 years for IgE-mediated disease 1, 8
• 80% acquire tolerance before age 3-4 years 6

Common Pitfalls in Symptom Recognition

Avoid these diagnostic errors: 1, 7

• Do not diagnose cow's milk allergy based solely on positive skin prick test or specific IgE without clinical correlation, as sensitization alone does not equal clinical allergy 7
• Do not assume gastrointestinal symptoms after milk indicate lactose intolerance, as cow's milk allergy is far more common in infants and young children 7
• Testing children under 5 years with atopic dermatitis for cow's milk allergy should occur ONLY if eczema persists despite optimized topical therapy, or if there is a reliable history of immediate reaction 1
• Recognize that 45% of individuals with food allergy have multiple food allergies, requiring comprehensive evaluation 4