"Sharing a toothbrush is likely no riskier than kissing a cohabiting partner. "
The Hidden World in Your Mouth
The human mouth is a complex ecosystem, hosting over 700 bacterial species. On any given day, roughly 200 species, plus various fungi and viruses, are present. Most are harmless or even beneficial.
The Risks of Sharing
While the oral microbiome is largely benign, harmful bacteria can be present. These include Streptococcus mutans (linked to tooth decay), Porphyromonas gingivalis, and Treponema denticola (both associated with gum disease). These pathogens can survive on toothbrushes.
- Drying helps, but it’s not enough: Allowing a toothbrush to dry between uses reduces oral bacteria, but it does not eliminate bacteria from nasal passages, skin, hands, or the bathroom environment. This includes threats like Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli.
Sharing vs. Kissing: The Comparative Risk
Dr. Samantha Byrne of the University of Melbourne offers a perspective on the risk. She suggests that sharing a toothbrush is likely no riskier than kissing a cohabiting partner. The reason? Couples living together already share about 38% of their oral microbiome.
The Real Danger: Blood-Borne Viruses
The experts draw a clear distinction between general bacteria and more serious threats.
"Immunocompromised individuals should avoid sharing toothbrushes." — Dr. Arosha Weerakoon
Dr. Weerakoon of the University of Queensland strongly discourages sharing toothbrushes due to the potential transmission of blood-borne viruses. Key risks include hepatitis B and C, which can survive on surfaces. Because brushing often causes minor gum trauma, even a small amount of blood can transfer these viruses. COVID-19 transmission is also possible through this route.
Safer Alternatives
If you find yourself without a toothbrush, experts recommend these options over borrowing one:
- Use toothpaste on a towel corner or your finger.
- Chew sugar-free gum to stimulate saliva production.
- Skip brushing for one night: It is not detrimental to your oral health.
How to Sanitize a Borrowed Brush (If absolutely necessary)
Dr. Byrne suggests a simple disinfection method: soak the borrowed toothbrush in a 50/50 solution of water and white vinegar for 10 minutes.