In a 13‑month‑old child recently weaned from formula to A2 whole cow’s milk who now has severe constipation, abdominal gas, irritability, bloody stools, perianal dermatitis, intermittent vomiting 2–3 hours after milk ingestion, eczema, and recent pneumonia, parainfluenza, and otitis media treated with steroids and antibiotics, what is the appropriate regimen of lactose‑free milk or hypoallergenic formula to manage suspected lactose intolerance and/or cow‑milk protein allergy?

Immediate Recommendation: Stop Whole Milk and Switch to Extensively Hydrolyzed Formula

Your child's symptoms—bloody stools, severe constipation, extreme fussiness, vomiting 2-3 hours after milk, gas, perianal dermatitis, and eczema—strongly suggest cow's milk protein allergy (CMPA), not lactose intolerance, and you should immediately discontinue all cow's milk products (including A2 milk and lactose-free milk) and switch to an extensively hydrolyzed formula (eHF). 1

Why This Is Not Lactose Intolerance

• Lactose intolerance does not cause bloody stools, eczema, or the constellation of symptoms your child is experiencing 2
• Lactose intolerance is primarily a digestive disorder causing gas, bloating, and watery diarrhea—not the immune-mediated inflammation that produces blood in stool 2
• Primary lactose intolerance is extremely rare in children under 2-3 years of age and has high racial predilection, being most common in dark-skinned populations 2
• The timing of vomiting (2-3 hours post-ingestion), bloody stools, and severe systemic symptoms point to an immune reaction to milk proteins, not lactose 3

Why This Is Cow's Milk Protein Allergy

Your child's presentation matches non-IgE-mediated CMPA, specifically a form called allergic proctocolitis with possible features of food protein-induced enterocolitis syndrome (FPIES):

• Bloody stools with mucus are the hallmark of allergic proctocolitis 1, 4, 3
• Vomiting 2-3 hours after milk ingestion is characteristic of FPIES 5, 3
• Severe constipation, gas, and perianal dermatitis are common manifestations of CMPA 6
• Eczema is present in 40-50% of infants with CMPA 7
• The dramatic improvement when you gave only formula last night is diagnostic—symptoms resolve within 72-96 hours of eliminating the trigger protein 1, 4

Specific Management Protocol

Step 1: Formula Selection (Start Immediately)

• Switch to an extensively hydrolyzed formula (eHF) such as Nutramigen, Alimentum, or Pregestimil 1
• eHF has an 80-90% success rate in managing CMPA 1
• Do NOT use soy formula—20-40% of infants with CMPA also react to soy due to cross-reactivity 5, 1
• Do NOT use lactose-free cow's milk—this still contains the allergenic milk proteins that are causing the problem 6
• If eHF fails after 2-4 weeks, consider amino acid-based formula (Neocate, EleCare) 3

Step 2: Expected Timeline for Improvement

• Bloody stools should resolve within 72-96 hours of starting eHF 1, 4
• Most infants return to their usual state of health within 3-10 days, with median resolution at 5 days 1
• Eczema may take 2-4 weeks to improve 6
• Constipation and fussiness should improve within the first week 1

Step 3: Monitoring During Transition

• Continue the eHF exclusively—do not mix with any cow's milk products 1
• Monitor stool patterns: blood should disappear first, then consistency should normalize 4
• Track irritability and sleep patterns as markers of improvement 1
• Watch for adequate weight gain and hydration 6

Step 4: Duration of Elimination

• Continue eHF for at least 6-12 months before attempting reintroduction of cow's milk 1, 4
• Most children with CMPA outgrow it by 1-2 years of age 4, 3
• Reintroduction must be done under physician supervision, not at home 1, 4

Critical Pitfalls to Avoid

• Do not try lactose-free milk—this is the wrong diagnosis and will not help 6, 2
• Do not use A2 milk or any "specialty" cow's milk—all contain the allergenic proteins (casein and whey) 6
• Do not attempt gradual reintroduction on your own—FPIES reactions can cause severe dehydration and shock requiring IV fluids 5, 3
• Do not use soy formula as an alternative—high cross-reactivity rate makes this inappropriate 5, 1
• Do not unnecessarily restrict other foods unless they also cause symptoms 5

When to Seek Urgent Care

Watch for signs of severe FPIES reaction if accidental milk exposure occurs:

• Projectile, repetitive vomiting (≥4 episodes) 5
• Extreme lethargy or pallor 5, 8
• Signs of dehydration (decreased urine output, sunken fontanelle, dry mucous membranes) 5
• Abdominal distention or hypothermia 5

These require immediate emergency department evaluation for IV hydration 5, 1

Additional Considerations

Eczema Management

• The eczema is likely related to the CMPA and should improve with formula change 7
• Continue appropriate skin care with emollients 7
• If eczema persists after 4 weeks on eHF, consider evaluation for other food triggers 7

Introduction of Solid Foods

• When introducing complementary foods, start with lower-risk options like vegetables (broccoli, cauliflower, pumpkin) and fruits (apple, pear) 5
• Avoid high-risk FPIES triggers initially: rice, oat, other grains, and legumes 5, 8
• Children with cow's milk FPIES have a 30% risk of reacting to solid foods, particularly rice and oat 1, 8
• Introduce new foods one at a time with 4-day intervals to monitor for reactions 5

Follow-up Plan

• Schedule follow-up with pediatrician within 1-2 weeks to confirm symptom resolution 1
• Consider referral to pediatric allergist or gastroenterologist if symptoms persist beyond 2-4 weeks on eHF 1, 4
• Nutritional consultation is recommended to ensure adequate calcium, vitamin D, and other nutrients during milk elimination 5