To decrease the morbidity and mortality of asthma, prevention and acute episode alarms have become indispensable. The triboelectric nanogenerator (TENG)-based wearable point-of-care (POC) medical service presents a potential opportunity to implement round-the-clock prevention and continuously monitor the respiratory signals of asthmatic patients. Herein, a self-switched triboelectric nanogenerator (SS-TENG) mediated by respiratory motions is developed to provide prevention and emergency functions for asthma. The SS-TENG can supply sustained and stable electrical energy by smooth breathing motion to deliver preventive drugs with a transdermal system. This device is switched to a pulse mode by a strong and rapid respiratory motion. The outputs can be improved with orders of magnitudes, thereby endowing it with high sensitivity and resolution for emergency alarms of acute asthma episodes. Consequently, short-range visual and long-range wireless alarm indications are successfully demonstrated to send emergent messages to the monitoring terminals. As a wearable POC medical device, this SS-TENG may provide the preventive, diagnostic, and therapeutic services for respiratory diseases.