Recurrent episodes of febrile dyspnoea: hypersensitivity pneumonitis caused by a household ultrasonic humidifier.

Hypersensitivity pneumonitis is an immune-mediated interstitial lung disease that presents with respiratory symptoms, with or without systemic symptoms, following exposure to an identified or unidentified external factor. It can be caused by extrinsic factors including household items such as ultrasonic humidifiers.We present an intriguing case of a previously healthy 50-year-old man who displayed recurrent episodes of progressive dyspnoea and fever after repeated exposure to his household ultrasonic humidifier.