VHOSPITAL.CLINIC · Differential Diagnosis
Asthma vs Hypersensitivity Pneumonitis
Clinical comparison — shared symptoms, key differences, distinguishing diagnostic tests, treatment pathways, and when to seek urgent evaluation.
Condition Overview
Condition A
Asthma
Asthma is a chronic inflammatory disease of the airways characterized by episodes of wheezing, breathlessness, chest tightness, and coughing. Triggers include allergens, exercise, cold air, and respiratory infections.
Condition B
Hypersensitivity Pneumonitis
Hypersensitivity pneumonitis (extrinsic allergic alveolitis) is an inflammatory lung disease caused by repeated inhalation of organic antigens. Farmer's lung and bird fancier's lung are classic examples; antigen avoidance is the most important intervention.
Shared Symptoms — Why They're Confused
Both conditions present with 2 overlapping symptoms, making clinical differentiation essential.
Key Clinical Differences
Asthma
- Episodic dyspnoea and wheeze, often allergic triggers
- IgE-mediated atopy common
- Responds well to bronchodilators and ICS
- Normal chest X-ray between attacks
Hypersensitivity Pneumonitis
- Diffuse lung inflammation from inhaled organic antigens (farmer's lung, bird fancier's)
- Restrictive rather than obstructive pattern
- Systemic symptoms: fever, myalgia 4–8 h post-exposure
- Chest X-ray shows diffuse interstitial infiltrates
Distinguishing Diagnostic Tests
| Test | Asthma | Hypersensitivity Pneumonitis |
|---|---|---|
| Spirometry | Obstructive; reversible post-bronchodilator | Restrictive pattern (reduced FVC, normal FEV1/FVC); not reversible |
| Serum precipitins / specific IgG | Negative — no precipitating antigen exposure | Positive precipitins to relevant antigen (e.g., Aspergillus, avian proteins) |
| HRCT | Normal or hyperinflation; mosaic attenuation (air trapping) | Ground-glass opacities, centrilobular nodules, mosaic attenuation |
Treatment Approaches
Asthma
- •Inhaled corticosteroids + SABA rescue
- •Allergen avoidance / immunotherapy
- •Biologics for severe eosinophilic asthma
Hypersensitivity Pneumonitis
- •Antigen avoidance (critical — removes the cause)
- •Oral corticosteroids for acute/subacute disease
- •Long-term immunosuppression (azathioprine) if progressive
When Doctors Consider Each Diagnosis
🔵 Consider Asthma when:
- →Atopic patient with episodic wheeze and clear allergen triggers
🟢 Consider Hypersensitivity Pneumonitis when:
- →Systemic symptoms 4–8 h after organic dust exposure; no wheeze predominance
Explore Each Condition in Detail
Related Clinical Pages
Asthma
Medical References
Content on this page is informed by evidence-based clinical sources including:
- World Health Organization (WHO)Global health guidance and disease classification
- National Health Service (NHS)UK clinical guidelines and patient information
- National Institute for Health and Care Excellence (NICE)Evidence-based clinical practice guidelines
- Centers for Disease Control and Prevention (CDC)US public health data and clinical recommendations
- PubMed – NCBIPeer-reviewed biomedical literature and clinical studies
- Cochrane LibrarySystematic reviews and meta-analyses in evidence-based medicine
Not sure which condition applies to you?
Describe your symptoms and get a structured clinical assessment — possible causes, red flags, and recommended next steps.
Start Free AI Analysis →