Rinsing your mouth with showerhead water after brushing teeth may increase the risk of bacterial infection under certain conditions, medical experts have warned. Those with chronic lung diseases or compromised immune systems should particularly review their daily hygiene routines, they said.
The Seoul National University Hospital's YouTube channel recently addressed this issue in a video titled "Stop Immediately: Rinsing Your Mouth With Showerhead Water."
According to the video, rinsing the mouth directly with showerhead water can elevate the risk of nontuberculous mycobacteria (NTM) infection. NTM belongs to the same mycobacteria family as tuberculosis bacteria but is primarily transmitted through environmental exposure rather than person-to-person contact. The bacteria have been detected not only in natural environments such as lakes, rivers and soil, but also in household and medical settings involving water, including showerheads, water pipes and humidifiers.
NTM is relatively resistant to chlorine disinfection and tends to adhere to surfaces, making it easy for the bacteria to form biofilms inside showerheads and hoses. The structure of hoses, where water tends to accumulate, provides particularly favorable conditions for bacterial growth. Rinsing the mouth with showerhead water directly exposes the oral cavity and upper respiratory tract to water droplets, potentially increasing the likelihood of inhaling the bacteria.
"If a showerhead is old, bacteria can attach inside the head and spread when you shower," said Lim Jae-jun, a professor of pulmonology at Seoul National University Hospital. "The habit of rinsing your mouth with showerhead water is something you should stop immediately."
Lim recommended replacing showerheads at least once every six months and paying special attention to hygiene management for older units.
However, medical professionals noted that NTM disease does not develop simply from regular showering or tap water use. In healthy individuals, the immune system typically eliminates the bacteria even after exposure, with most cases passing without symptoms. In contrast, patients with chronic obstructive pulmonary disease (COPD), bronchiectasis, lung damage from past tuberculosis, or those undergoing immunosuppressive treatment face a relatively higher risk of developing pulmonary disease.
Overseas cases have also pointed to lifestyle habits as a contributing factor. According to Vietnamese media reports, a Chinese woman who visited a hospital for chronic coughing was diagnosed with NTM pulmonary disease. Investigation revealed she had been using the same showerhead for more than 10 years without replacement. Medical staff suggested that the old showerhead combined with her mouth-rinsing habit may have contributed to the infection.
Experts recommend periodically disassembling and cleaning showerheads and hoses to reduce infection risk, and ensuring water does not remain stagnant inside for extended periods. Using sink tap water for brushing teeth and avoiding the habit of rinsing the mouth directly during showers is considered a safer hygiene practice, they advised.
