# The Listerine Phenomenon: Why does it make my canker sore feel so much better? **URL:** \ **Category:** Factual Questions\ **Created:** [November 2, 2004, 10:05pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621 "2004-11-02T22:05:36Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Cockatiel](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Cockatiel](https://boards.straightdope.com/u/Cockatiel)\ **Post date:** [November 2, 2004, 10:05pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/1 "2004-11-02T22:05:36Z")
It doesn’t seem to make sense, but whenever I use Listerine and have a canker sore, it numbs it. Seeing as Listerine burns like hell, I don’t get how it can physically numb something like this. My theory is that it hurts so bad using it, that when it’s over, your mouth is desensitized. But what do I know? Any ideas of what causes this phenomenon? 😕 ---
**Author:** ![bouv](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@bouv](https://boards.straightdope.com/u/bouv)\ **Post date:** [November 2, 2004, 10:07pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/2 "2004-11-02T22:07:47Z")
I dunno, but I have a similar feeling, except that while using it it HURTS LIKE HELL! It’s a red hot poker on my canker sore…but after I spit out, and rinse a few times, it feels better than before. As you said, it might be just the lack of SEVERE PAIN, or the pain nerves got overwhelmed and went into hibernation, who knows. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 2, 2004, 11:16pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/3 "2004-11-02T23:16:36Z")
Listerine contains camphor, which is a fair topical anesthetic. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [November 2, 2004, 11:20pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/4 "2004-11-02T23:20:26Z")
Are you sure it’s a canker sore and not a “cold” sore, which is activation of the herpes simplex I virus? If the latter, I’ve had great success with Curasore, which contains ether. You can buy it OTC, but you’ll have to ask the pharmacist for it since it is not kept on the shelves. I don’t know if it will be as good for canker sores, but may be worth a try. (It’s inexpensive.) ---
**Author:** ![OhFace](https://avatars.discourse-cdn.com/v4/letter/o/ecccb3/32.png) [@OhFace](https://boards.straightdope.com/u/OhFace)\ **Post date:** [November 2, 2004, 11:57pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/5 "2004-11-02T23:57:12Z")
> [@Qadgop the Mercotan](#): > > Listerine contains camphor, which is a fair topical anesthetic. Yes. I didn’t believe this until I got my tongue pierced. I was given listerene to rinse with first and the piercer told me it would also numb the outside of my tongue. I didn’t believe a word of it, but it actually did. That needle going through the middle of my tongue was another story though! ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [November 3, 2004, 1:20am UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/6 "2004-11-03T01:20:10Z")
**Cockatiel:** You didn’t ask this, but since you have canker sores you might be interested. I used to get them quite frequently, until I read here that one known cause (out of several) is a sensitivity to sodium lauryl sulfate, which is a common ingredient in toothpaste. Since I switched to an SLS-free toothpaste (Jason Powersmile), I haven’t had a single canker sore. It’s been well over a year now. Might be worth a try. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 3, 2004, 1:51am UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/7 "2004-11-03T01:51:51Z")
I have had the same experience as the OP, in fact, for some really bad mouth cuts I had Listerine was the only form of pain relief I had. It was very effective, numbing the cuts for 2-3 hours (after the initial 5 minutes of eye-watering pain), and it was much appreciated. ---
**Author:** ![Civil\_Guy](https://avatars.discourse-cdn.com/v4/letter/c/d78d45/32.png) [@Civil\_Guy](https://boards.straightdope.com/u/Civil_Guy)\ **Post date:** [November 3, 2004, 2:31am UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/8 "2004-11-03T02:31:50Z")
For the record, straight from the bottle (‘Natural Citrus Flavor’, FWIW): "Active Ingredients Eucalyptol 0.092% Menthol 0.042% Methyl salicylate 0.060% Thymol 0.064% Purposes [of active ingredients]: Antiplaque / antigingivitis" Editorial comment - a couple of these are also balms (however balms work), right? Also educational: "Inactive Ingredients Water, alchohol (20.6%), sorbitol solution, flavoring, poloxamer 407, benzoic acid, sucralose, sodium benzoate, cochineal extract" …and honest to goodness, that alchohol percentage is a direct quote. For What It’s Worth. ---
**Author:** ![Civil\_Guy](https://avatars.discourse-cdn.com/v4/letter/c/d78d45/32.png) [@Civil\_Guy](https://boards.straightdope.com/u/Civil_Guy)\ **Post date:** [November 3, 2004, 2:33am UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/9 "2004-11-03T02:33:56Z")
Well, no it isn’t. I typed it in wrong. The percentage of alchohol is 21.6%. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 3, 2004, 2:35am UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/10 "2004-11-03T02:35:54Z")
Damn! They pulled the camphor! :smack: ---
**Author:** ![pokey](https://avatars.discourse-cdn.com/v4/letter/p/ebca7d/32.png) [@pokey](https://boards.straightdope.com/u/pokey)\ **Post date:** [November 3, 2004, 4:35am UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/11 "2004-11-03T04:35:33Z")
Counter-irritants like menthol or eucalyptol numb your mouth with super mouth burning action. here is a link: [http://www.jr2.ox.ac.uk/bandolier/booth/painpag/topical/Topintro.html](http://www.jr2.ox.ac.uk/bandolier/booth/painpag/topical/Topintro.html) After I use the generic mouthwash my tongue is blue and can’t feel anything and I’m crying. It’s a weird way to start the day. ---
**Author:** ![Edward\_The\_Head](https://avatars.discourse-cdn.com/v4/letter/e/ce73a5/32.png) [@Edward\_The\_Head](https://boards.straightdope.com/u/Edward_The_Head)\ **Post date:** [November 3, 2004, 12:43pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/12 "2004-11-03T12:43:07Z")
> [@Cervaise](#): > > **Cockatiel:** You didn’t ask this, but since you have canker sores you might be interested. I used to get them quite frequently, until I read here that one known cause (out of several) is a sensitivity to sodium lauryl sulfate, which is a common ingredient in toothpaste. Since I switched to an SLS-free toothpaste (Jason Powersmile), I haven’t had a single canker sore. It’s been well over a year now. Might be worth a try. I found out the exact same thing. I switched to a new type of toothpaste in June, I got huge sores on my lips, twice. They hurt for weeks until I finally looked it up on-line and switched to something without SLS. My sores cleared up pretty quick and I haven’t had any since. The only problem I’ve found is finding tooth paste without SLS in it. Most of the chain stores do not carry it. I have to look in the natural food stores. ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [November 3, 2004, 2:53pm UTC](https://boards.straightdope.com/t/the-listerine-phenomenon-why-does-it-make-my-canker-sore-feel-so-much-better/272621/13 "2004-11-03T14:53:12Z")
> [@Civil Guy](#): > > "Inactive Ingredients > > Water, alchohol (20.6%), sorbitol solution, flavoring, poloxamer 407, benzoic acid, sucralose, sodium benzoate, cochineal extract" > > …and honest to goodness, that alchohol percentage is a direct quote. Since when is alchohol an inactive ingredient, especially when it is that high a percentage?