Diagnosis: Irritant-Induced Laryngeal Edema (Chemical Laryngitis)
The most likely diagnosis is irritant-induced laryngeal edema from ammonia exposure, not an asthma exacerbation. The key distinguishing feature is the inspiratory stridor loudest over the neck with normal vital signs, which indicates upper airway (laryngeal) involvement rather than lower airway obstruction typical of asthma 1, 2, 3.
Clinical Reasoning
Why This Is NOT Asthma
While this patient has a history of asthma and was exposed to a known respiratory irritant, several critical features point away from an asthma exacerbation:
Stridor location and timing: Inspiratory stridor loudest over the neck is characteristic of upper airway obstruction 2, 3. In asthma, wheezing is predominantly expiratory and louder over the chest wall 3.
Normal vital signs: Asthma exacerbations typically present with tachypnea, tachycardia, and potentially hypoxemia depending on severity 4. The presence of normal vitals with prominent stridor suggests a localized upper airway process.
Anatomic localization: The neck as the loudest point of sound transmission indicates laryngeal or tracheal involvement, not the diffuse bronchospasm of asthma 3.
Why This IS Irritant-Induced Laryngeal Injury
Ammonia is one of the strongest airway irritants in cleaning products 5, 6. The evidence clearly establishes:
- Ammonia exposure during cleaning activities can reach concentrations of 0.6-6.4 ppm 6
- Ammonia is classified as an alkaline agent and strong airway irritant 5
- High-level irritant exposure can cause acute upper airway inflammation and edema
Differential Consideration: Vocal Cord Dysfunction
Vocal cord dysfunction (VCD) should be considered in the differential, as it can mimic asthma and presents with inspiratory stridor 1. However, VCD typically:
- Shows variable flattening of the inspiratory flow loop on spirometry
- Requires direct visualization during an episode for diagnosis
- Is less likely with acute chemical exposure as the clear precipitant
The acute temporal relationship (one hour after ammonia exposure) and the clinical presentation strongly favor direct chemical irritation causing laryngeal edema rather than VCD.
Clinical Pitfalls to Avoid
Do not reflexively treat this as asthma simply because of the patient's history. While asthma patients may be more susceptible to irritant effects 5, treating isolated upper airway obstruction with bronchodilators alone will be ineffective and may delay appropriate management.
Monitor closely for progression: Although irritant-induced laryngeal edema is typically self-limited with supportive care, severe cases can progress to acute airway compromise 7. Serial assessments of stridor severity, work of breathing, and oxygen saturation are essential.
Management Approach
The patient requires:
- Immediate assessment of airway patency and ability to protect the airway
- Humidified oxygen and cool mist therapy to reduce laryngeal inflammation
- Corticosteroids (systemic) to reduce upper airway edema
- Observation for potential progression requiring airway intervention
- Removal from exposure and avoidance of further irritant contact
If lower airway symptoms develop (expiratory wheezing, decreased breath sounds), then concurrent asthma treatment with bronchodilators and inhaled corticosteroids would be appropriate 4.