Two questions:
-Why does it burn? (“because of the alcohol” is not an answer to this question)
-Adding even a small amount of water makes it not burn. Is it as effective? Why or why not? Dentist says no but I’m not so sure.
Thanks.
Edit: Hard to believe this hasn’t come up before but search isn’t working for me and I’ve been wondering about this every night before bed since I bought that bottle of Listerine a couple weeks ago.
Obviously Listerine burns because you’ve been leaving it out in the Phoenix sun. Putting any liquid heated to just short of the boiling point in your mouth is going to burn.
Actually it would be more appropriate to say Listerine burns, not because of the alcohol, but because of the alcohols. The active ingredients in Listerine are Methyl Salicylate, Thymol, Eucalyptol, Menthol and Ethanol. Four out of five of these are alcohols (esters).
What probably doesn’t burn would be the menthol – it’s a cool minty flavor but has anesthetic and mild antiseptic properties, the eucalyptol – also a minty flavoring but more medicine like, also an anesthetic/mild antiseptic and Thymol – a more herby flavor and a good antiseptic, but with anesthetic properties (also an ingredient used in ancient Egypt to help preserve mummies). These three esters would have more of a numbing effect than a burning effect.
The burning is more likely due to the ethanol and the methyl salicylate. Ethanol acts as a solvent for the botanical oils in the previous three ingredients, dissolving them in a solution of 21.6% – 26.9%. The ethanol also dissolves some of the stuff in your mouth. Ethanol breaks down lipids (fatty molecules) and could be causing some of the inner cells of your mouth to break down, essentially stripping some of your cells like stripping paint off of a wall. Ethanol in high enough concentrations could be an antiseptic, but at the concentrations used in Listerine would probably be ineffective.
Methyl Salicylate is an ester of salicylic acid and is a very effective antiseptic. Salicylic acid is used in cosmetics as a debriding agent. It’s in dandruff shampoos to remove dead skin, face scrubs to exfoliate, etc. Salicylic acid is also more commonly known as Aspirin. Methyl Salicylate, as well as some of the other active ingredients in Listerine, is also an important ingredient in topical analgesics like Icy Hot or Tiger Balm. These also have a cooling, numbing effect while the Salicylic acid penetrates the skin to reduce inflamation. Methyl Salicylate is also known as Oil of Wintergreen, a popular flavoring. Wintergreen oil can be used to kill a variety of skin and nail fungus, the wiki page mentions using it as a treatment for toe nail fungus by applying it daily for three months.
Between the ethanol breaking down cells and the methyl salicylate debriding dead tissues I would expect Listerine to burn a lot more than it does. Fortunatley the other three esters are there to numb things up a bit. Adding water, even a little bit, changes the concentration of the alcohol enough to release more of the oils which would anestisize things further, but would reduce the efficacy of these oils in killing “the germs that cause bad breath.” Since Listerine is an oral hygene product and not a cocktail mixer, and ethanol can cause more damage to the soft skin cells than desired at higher concentrations, I would think that Listerine only uses as much ethanol as needed to hold the oils in place to make them effective. A tiny bit of water would put this out of balance resulting in an oral rinse that is essentially bad tasting Aspirin water.
Resources:
Methyl salicylate - http://en.wikipedia.org/wiki/Methyl_salicylate
Salicylic acid - http://en.wikipedia.org/wiki/Salicylic_acid
Thymol - http://en.wikipedia.org/wiki/Thymol
Listerine - http://en.wikipedia.org/wiki/Listerine
Was that the best-ever first response in GQ?
Almost. There’s no mention of the gum disease GINGIVITIS!! 
May I ask another Listerine question? Why is it (IME) so great for toothaches? If I have a filling fall out and that tooth is starting to hurt, swish swish swish with the green stuff and no more pain.
Johnny Walker works too, but my wife looks at me suspiciously when I’m carrying around a bottle of that stuff.
Yeah, it might’ve been. It was pretty damn good. Thank you, nd_n8.
Very thorough, but I must quibble: alcohols are not esters. Esters are not alcohols.
Add me to the best ever first response bandwagon!
As for this, I’ve always assumed it’s because Listerine’s so good at flushing away tiny food particles (which would irritate the nerve) and also covering the area with antiseptic. I’d love this to be clarified though, as I suggest it as a remedy to friends and family but am obviously a little vague as to why it seems to work!
LISTERINE was popular in the era of national prohibition, because of its high alcohol content. It is pretty nasty tasting stuff-drunks used to mix it with lime juice for a cheap marguerita.
any idea what it costs them to make this stuff?
You are right, esters are produced as a reaction between alcohol and acid. Four of the five active ingredients are esters, not alcohols specifically. They were esterisized by a reaction with alcohol and acid but they are not technically alcohol.
I was thinking about the alcohol sugars when I wrote that. Alcohol sugars are sugars that have been reduced to a secondary hydroxyl group, esters are hydroxyls that have been reduced to an oxyl group. I apologize for my confusion.
My guess would be that, between the alcohol numbing the nerve, the antiseptics killing any germs that could cause inflammation and the anasthetics in Listerine it should put a toothache to bed.
But it’s just not as much fun as Johnny Walker.
Also note that the Thymol is a depressant (and an unregulated one at that) so with Listerine there could be an effect similar to using a shot of weak tequila to wash down a low dose valium. That can’t be good for you.
If you think Listerine burns now, take a big swig of very warm water after you spit out your mouthwash. Ye-Ouch!
What’s the cause there?
If you’re talking about a scalding sensation, it’s because your brain interprets cold (from the previously-described menthol in Listerine) and warm (from the water) together as extreme heat and thinks you just swigged a mouthful of boiling water, more or less.
nm
I’m one of those lazy people who just chugs the Listerine from the bottle instead of pouring it into a glass before rinsing. When I have a sore throat or cold, I like to gargle with it. I’m the only one using the Listerine, so there isn’t a chance of someone else’s germs getting on the bottle, but my own would.
Do the antiseptic properties of Listerine keep me from “making myself sick” from any of my own germs that might be on the bottle, or am I risking re-infecting myself by not pouring it into a glass when I use it?