Hydrogen Peroxide Inhalation During Dental Whitening Leading to Massive Hemoptysis and Tumor-Like Endobronchial Obstruction: A Case Report.

Hydrogen peroxide (H₂O₂) is widely used in dental whitening and is generally considered safe when applied under professional supervision. However, accidental aspiration may cause unexpected airway complications. A 55-year-old North African woman presented with massive hemoptysis, preceded by a 3-month history of persistent dry cough and an earlier minor hemoptysis episode. Symptoms had begun shortly after a dental whitening procedure using 35% H₂O₂, complicated by intense pharyngeal pain, ulcerative lesions, and severe coughing. Chest imaging showed complete left lower lobe atelectasis due to an intraluminal soft-tissue lesion, with associated parenchymal consolidation. Flexible bronchoscopy was attempted but interrupted due to complications, after which the patient expectorated thick mucus. Follow-up imaging one month later demonstrated complete resolution of the lesion and full lung re-expansion. This case highlights the potential for severe airway injury following dental use of high-concentration H₂O₂. Awareness of such iatrogenic exposures is essential when evaluating unexplained hemoptysis and atelectasis.