Could a 6‑year‑old with a persistent deep wet cough for 6–12 months after an upper respiratory infection, normal laboratory studies, negative allergy testing, mild mid‑lung consolidation on chest radiograph, and temporary improvement with amoxicillin have a milk allergy from mold‑contaminated dairy?

Protracted Bacterial Bronchitis, Not Milk Allergy

This 6-year-old has protracted bacterial bronchitis (PBB), not a milk sensitivity or mold-related allergy. The clinical pattern—deep wet cough lasting months after viral infections, temporary resolution with amoxicillin, mild consolidation on chest X-ray, and negative allergy testing—is pathognomonic for PBB requiring extended antibiotic therapy, not dietary modification. 1, 2

Why This Is PBB, Not Allergy

The temporary response to amoxicillin followed by recurrence is the hallmark of inadequately treated bacterial bronchitis, not food allergy. 1 Key distinguishing features:

• Milk allergy does not cause isolated wet cough with radiographic consolidation. Food allergies typically manifest as urticaria, angioedema, gastrointestinal symptoms, or anaphylaxis—not chronic productive cough. 3
• The negative scratch allergy test effectively rules out IgE-mediated milk allergy. 3
• Mold exposure causing "milk sensitivity" has no evidence base in pediatric respiratory medicine. This is not a recognized clinical entity. 3
• The wet, deep quality of the cough indicates lower airway mucus hypersecretion from bacterial infection, not allergic inflammation which typically produces dry cough. 1, 4

The Critical Treatment Error

Your patient is receiving inadequate antibiotic duration—1 month is insufficient for PBB. 1, 2 The CHEST guideline algorithm:

• Initial treatment: 2 weeks of amoxicillin-clavulanate (not plain amoxicillin, which lacks coverage for β-lactamase-producing H. influenzae and M. catarrhalis). 1, 2
• If wet cough persists after 2 weeks: extend for an additional 2 weeks (total 4 weeks). 1, 2
• Reassess after 4 weeks total: If cough still persists, proceed to bronchoscopy with quantitative BAL cultures, chest CT, and immunologic evaluation. 2

The recurrence after each cold represents new bacterial colonization superimposed on incompletely treated airway inflammation, not treatment failure. 1, 5

Immediate Management Plan

Switch from amoxicillin to amoxicillin-clavulanate for 4 weeks. 1, 2 Rationale:

• Plain amoxicillin misses β-lactamase-producing organisms (present in 30-40% of H. influenzae and most M. catarrhalis). 1
• The 4-week duration addresses persistent bacterial density in the lower airways. 1, 2
• Dose: 90 mg/kg/day of amoxicillin component divided twice daily (high-dose formulation for resistant S. pneumoniae). 1

Complete the full 4-week course even if cough resolves earlier, as premature discontinuation leads to relapse. 2

Red Flags Requiring Urgent Specialist Referral

Before starting antibiotics, verify absence of these specific cough pointers: 2, 3

• Coughing with feeding → aspiration syndrome requiring swallow study and ENT/GI evaluation 2, 3
• Digital clubbing → bronchiectasis or interstitial lung disease requiring chest CT 2, 3
• Failure to thrive → cystic fibrosis, immunodeficiency, or bronchiectasis requiring comprehensive workup 3
• Unilateral findings on exam → retained foreign body requiring bronchoscopy 3

None of these appear present in your patient, so proceed with antibiotic therapy. 2

What to Do If Cough Persists After 4 Weeks

Failure to respond to 4 weeks of appropriate antibiotics mandates investigation for alternative diagnoses: 1, 2

• Chest CT to evaluate for bronchiectasis (5.9-fold increased risk in non-responders) 2
• Flexible bronchoscopy with quantitative BAL cultures to identify atypical organisms or confirm microbiologically-based PBB 1, 2
• Immunologic evaluation (immunoglobulin levels, vaccine titers, lymphocyte subsets) to exclude immunodeficiency 3
• Consider pertussis testing if paroxysmal cough with post-tussive vomiting develops 1, 3

Why Recurrence After Each Cold Happens

Viral upper respiratory infections transiently impair mucociliary clearance and epithelial integrity, allowing bacterial colonization. 1, 5 In children with incompletely treated PBB:

• Residual airway inflammation persists between episodes 5
• Each new viral infection triggers bacterial overgrowth 5
• This cycle is broken by adequate-duration antibiotics (4 weeks), not by eliminating dietary triggers 1, 2

Common Pitfall to Avoid

Do not diagnose asthma and prescribe inhaled corticosteroids. 6, 7 This child has:

• Wet cough (asthma causes dry cough) 4, 7
• No wheeze, dyspnea, or exercise limitation (required for asthma diagnosis) 6, 7
• Radiographic consolidation (asthma shows hyperinflation or normal findings, not consolidation) 6
• Response to antibiotics (asthma responds to bronchodilators/steroids, not antibiotics) 6, 7

Misdiagnosing PBB as asthma leads to unnecessary steroid exposure and progression to bronchiectasis. 2, 8

Long-Term Prognosis

Even with appropriate treatment, 17.7% of children have persistent symptoms 5-14 years later, and 12.9% develop abnormal spirometry. 8 This underscores the importance of:

• Early, adequate-duration antibiotic therapy to prevent progression 2, 8
• Long-term follow-up with periodic spirometry to detect subclinical lung function decline 8
• Low threshold for repeat imaging if recurrent PBB episodes occur 8

Eliminating milk will not prevent these outcomes; adequate antibiotic therapy might. 1, 2, 8