 Bad breath is an underestimated problem affecting a significant proportion of the global population. It seems most people regularly report encountering people with halitosis. Masking agents are frequently used to cover up bad breath, but studies have shown that the use of mouth rinses, sprays, or mints containing an agreeable masking odor only have short-term effects since you're not treating the underlying cause. So the exclusive uses of masking products can never be truly considered an effective solution to the problem. The cause of bad breath is oral putrefaction. The degradation of certain amino acids mostly derived by bacterial breakdown of proteins in your mouth. Specifically, bacteria degrade the sulfur-containing amino acids, such as cysteine and methionine, into stinky compounds like the rotten egg gas hydrogen sulfide, so-called volatile sulfur compounds. If you measure these compounds spewing out of people's mouths with machines with names like breath-tron, tooth brushing alone does not significantly reduce oral malodour. Brushing alone reduces sulfur breath compounds from more than 450 down to about 300, but that's still above the stinky breath threshold of 250. Add tongue cleaning, and you can drop that down to right around the threshold, but adding an antiseptic mouthwash and antibacterial mouthwash did even better. So what's the best mouthwash to use? To find out, researchers used the cysteine challenge test. Instead of giving people dairy products, which contain the protein casing, which is rich in the sulfur amino acid cysteine, they just had the participants swish directly with some cysteine, and then followed effectiveness using odorograms. For example, tooth brushing. When people swished with cysteine before brushing their teeth, here's the spike in stinky sulfur compounds spewing out of the mouths. When they brushed their teeth with water and squished again at various times over the rest of the day, the spikes pretty much looked the same, meaning tooth brushing with water didn't remove many bad breath bacteria since the subjects were spewing out similar spikes, starting just 20 minutes later. Brushing with toothpaste works better, see how it knocks down the next spike of stinky compounds before the bacteria slowly grow back throughout the day. What about using a tongue scraper? Here's the odorogram. Tongue scraping knocks it down by about half before coming back over the next few hours. What about chewing gum? Here's that odorogram. Some effect that disappears over the subsequent few hours. What about various mouthwash? First of all, rinsing with water. Useless. Can be helpful for morning breath to rinse any stagnation that occurred overnight, but during the day just rinsing with water isn't clearing many bad breath bacteria. And swishing with scope mouthwash? Just as useless as water. Scope is an antibacterial mouthwash, but it must not be good at killing the specific bacteria that cause bad breath. Paradex, though, cleaned house, killing off those bacteria even seven hours later. What is Paradex? That's just a brand name for chlorhexidine. Uh-oh, we know about that from this video. Chlorhexidine doesn't just get rid of bad breath bacteria. It also kills off the good bacteria on your tongue that helps you make nitric oxide, which protects your arteries. And so chlorhexidine can raise your blood pressure. And that's not all. Chlorhexidine can stain your teeth. That's not what you want in a mouthwash. Adverse effects are not rare. Tooth staining, the buildup of tartar, taste disturbance, and damage to the lining of your mouth have all been reported with the use of chlorhexidine in about 9 out of 10 people. 88% of people suffer various side effects. But hey, chlorhexidine may be better than mouth washes with hydrogen peroxide, which may be carcinogenic, potentially increasing your risk of mouth cancer. That's not just based on studies on rodents either. Cultures of human mouth lining cells show significant DNA damage. Tri-closan was another common antibacterial ingredient in mouth washes now effectively banned in over-the-counter products. Tongue scraping alone doesn't always resolve the problem of holotosis. So what can we use? If that bath persists after improving tongue and dental hygiene, inactive zinc-based mouth rinse can be introduced. Zinc binds directly to the volatile sulfur compounds and prevents them from gassing out of your mouth. Mouth rinses containing zinc chloride without alcohol have been found to instantly, though temporarily, be effective for holotosis. Researchers looked at eight mouth rinses, and the most effective was a zinc chloride one, and the least effective was Colgate plaques. In fact, both of the alcohol rinses were found to be the least effective. The thought is that they may exacerbate holotosis by drying up your mouth. Here are some Sistine Challenge testing results with different concentrations of zinc chloride. Note that all forms of zinc don't work the same, though. Zinc chloride is very effective, but zinc gluconate, which was the difference between regular listerine and an advanced listerine, didn't seem to work as well.