What is the most likely diagnosis and recommended management for a patient with a chronic non‑productive cough that worsens seasonally and with exposure to dog dander, without nasal congestion?

Chronic Non-Productive Cough with Seasonal Worsening and Dog Dander Allergy

This patient most likely has cough-variant asthma or nonasthmatic eosinophilic bronchitis triggered by allergic rhinitis, and should be started immediately on a trial of inhaled corticosteroids (budesonide 400 μg twice daily or equivalent) for 2-4 weeks while avoiding dog exposure.

Most Likely Diagnoses

The clinical picture—chronic dry cough worsening seasonally with known pet dander allergy but notably without nasal congestion—points to two primary considerations:

1. Cough-Variant Asthma (CVA)

• Cough may be the only manifestation of asthma without wheezing or dyspnea 1, 2
• Allergic triggers (dog dander, seasonal allergens) are classic precipitants
• No currently available tests can reliably exclude a corticosteroid-responsive cough 1

2. Nonasthmatic Eosinophilic Bronchitis (NAEB)

• Presents with isolated chronic cough without airflow obstruction or bronchial hyperresponsiveness 3
• Associated with eosinophilic airway inflammation
• Responds dramatically to inhaled corticosteroids 3, 4

3. Upper Airway Cough Syndrome (UACS) - Less Likely Here

While allergic rhinitis commonly causes chronic cough 1, 5, the absence of nasal congestion makes this less probable as the primary driver, though it could be a contributing factor.

Diagnostic Approach

Initial evaluation should include:

• Spirometry with bronchodilator response
• Consider bronchial provocation testing (methacholine challenge) if spirometry is normal 1
• Key distinction: A negative bronchial provocation test excludes asthma but does NOT rule out steroid-responsive cough 1

However, extensive testing is NOT required before treatment. The guidelines explicitly recommend empiric treatment trials based on most probable causes 1.

Treatment Algorithm

Step 1: Immediate Actions

1. Eliminate environmental triggers: Strict avoidance of dog exposure 3
2. Verify no ACE inhibitor use: No patient with troublesome cough should continue ACE inhibitors 1
3. Confirm non-smoker status: Smoking is one of the commonest causes of persistent cough 1

Step 2: First-Line Empiric Treatment

Start inhaled corticosteroids immediately 2, 3:

• Budesonide 400 μg twice daily (or equivalent ICS)
• Duration: 2-4 weeks minimum
• Rationale: Both CVA and NAEB respond to ICS, making this the most efficient first step 1, 2, 3

Response assessment:

• If cough resolves within 2 weeks: Likely eosinophilic airway inflammation (CVA or NAEB) 1
• If no response after 2 weeks: Cough is unlikely due to eosinophilic inflammation 1

Step 3: If Partial or No Response

Consider adding treatment for allergic rhinitis (even without prominent nasal symptoms):

• Intranasal corticosteroid for 1 month trial 1
• Note: Second-generation antihistamines are ineffective for cough and should NOT be used 2
• First-generation antihistamine/decongestant combinations may help if upper airway symptoms emerge 2

Step 4: If Still Refractory

Consider gastroesophageal reflux disease (GERD):

• GERD is a common reason for treatment failure 1
• Reflux-associated cough may occur WITHOUT gastrointestinal symptoms 1
• Trial: Proton pump inhibitor (omeprazole 20-40 mg twice daily before meals) for minimum 8-12 weeks 1

Step 5: Escalation for Severe/Refractory Cases

• Short course oral corticosteroids (prednisone 30-40 mg daily for 1-2 weeks) followed by ICS 2
• Consider leukotriene receptor antagonist before escalating to systemic steroids 2
• Referral to specialist cough clinic 1

Critical Pitfalls to Avoid

1. Don't dismiss upper airway disease just because congestion is absent: There is poor association between various upper airway symptoms and cough 1

2. Don't wait for extensive testing: A combination of selected diagnostic testing and empirical treatment trials is most cost-effective 1

3. Don't use newer non-sedating antihistamines for cough: They are ineffective 2

4. Don't stop ICS too early: If response is good, continue for at least 3-4 weeks before attempting to taper

5. Don't forget GERD: It's frequently overlooked and can coexist with other causes 1

Why This Approach Works

The seasonal pattern and dog dander allergy strongly suggest an allergic/eosinophilic mechanism. Most cases of troublesome cough reflect the presence of an aggravant (asthma, environmental allergens, GERD, upper airway pathology) in a susceptible individual 1. The absence of nasal congestion doesn't exclude allergic mechanisms—it simply shifts the probability toward lower airway involvement (CVA or NAEB) rather than classic allergic rhinitis.

The empiric ICS trial is both diagnostic and therapeutic, with excellent safety profile and high likelihood of benefit if the underlying mechanism is eosinophilic inflammation 2, 3.