In ads on TV, it all looks so simple. People use mouthwash, it instantly neutralises all the nasty bacteria hiding in their mouths, and – just like that – their dental hygiene is assured.
But what's really going on when you rinse a cap-load of antibacterial chemicals around your mouth? What does that to your body, and to other kinds of microorganisms that may actually be beneficial to health?
As a study showed last year, the downstream effects can be surprising, and far-reaching too, affecting much more than just your dental wellbeing.
In an experiment led by scientists from the UK and Spain, researchers found that the simple act of using mouthwash after exercising can reduce one of the benefits of exercise: lowering blood pressure.
When you exercise, your blood vessels open in response to the production of nitric oxide, which increases the diameter of blood vessels. This process is called vasodilation, and it increases blood flow circulation to active muscles.
For a long time, researchers thought this only happened during exercise, but in more recent years, evidence has shown that circulation stays high (meaning blood pressure is lowered) even after exercise – thanks to how bacteria interact with a compound called nitrate, which forms when nitric oxide degrades.
"Research over the last decade has shown that nitrate can be absorbed in the salivary glands and excreted with saliva in the mouth," explains physiology specialist Raul Bescos from Plymouth University.
"Some species of bacteria in the mouth can use nitrate and convert into nitrite – a very important molecule that can enhance the production of nitric oxide in the body."
Once nitrite is produced and swallowed with saliva, it becomes absorbed into blood circulation and reduces back to nitric oxide, which keeps blood vessels wide and lowers blood pressure.
But according to this small study, it looks like this biological mechanism can be significantly interrupted if anti-bacterial mouthwash gets added into the post-exercise mix.