As you know, in households all across America the week between Christmas and New Year’s Day is reserved for the annual tradition of amateur home science experiments. This year in the manse of the west coast Madejs we’ll be getting to the bottom of our nation’s most notorious scourge, one both hissed at by Tea Partiers during Republican presidential debates and downward-fingerwiggled by Occupy protestors: morning mouth slime caused by mouthwash.

The Problem
You might be familiar with mouth slime, AKA “mouth boogers,” if you use any type of bedtime mouthwash, like Listerine Total Care or Crest Pro-Health. Such rinses are less geared toward freshening breath and more toward oral health or teeth whitening, so you use them at night to allow the active ingredients to work while you sleep. For example, I swish with a fluoride rinse on the advice of my dentist to help protect the parts of my teeth exposed from receding gums. My wife Sophie uses it too out of pure glee for dental care, and we’ve both noticed that in the morning we often wake up with a kind of sticky white slime in our mouths, between the lips and gums. It takes a lot of rinsing and skilled tongue work1 to get rid of it, so it’s kind of annoying and gross, but the slime presents no danger… SO FAR! Nevertheless, we are setting out to discover what causes mouth slime.

The Theory
A wee bit of the ol’ Google uncovers the news that mouth slime is a common problem among mouthwash users, but not a reliable explanation. The most widely accepted one comes via secondhand reports from dentists: that mouth slime is congealed saliva caused by peroxide in whitening rinses. But nay say I! To begin with, I don’t use a whitening mouthwash, and neither the store-brand or brand-name mouthwash I use lists peroxide as an active or inactive ingredient. Sophie parries that attack by noting that we use a whitening toothpaste, which could provide the necessary slime-birthing component. I counter with the fact that the amount of mouth slime we experience clearly varies in conjunction with the brand of mouthwash in play.2 That shouldn’t happen if the toothpaste is the determining factor. Still, our toothpaste brand also changes frequently, so it’s possible that I’ve attributed mouth slime variations to a switch in rinse when they’re actually due to a different toothpaste. Plus mouthwash contains all sorts of emulsifiers, anti-caking agents, and detergents, so it seems plausible that a specific inactive ingredient in one of the mouthwashes could interact with an ingredient in toothpaste to result in coagulated saliva. Based on the available evidence, it seems worth testing to see what kind of product combinations produce the most slime.

The Method
Starting tonight for the next eight days, Sophie and I will brush and rinse with a different combination of toothpastes and mouthwashes each night. We’ll use our two most common mouthwashes: Listerine Total Care Zero (a no-alcohol rinse) and Rite Aid Tooth Care (a store-brand with alcohol). In my experience, the former regularly produces mouth slime, while the latter doesn’t. We’ll be paring those with two toothpastes: Colgate Cavity Protection (standard fluoride toothpaste) and Colgate Total Advance Whitening (a toothpaste that contains whitening agents and that we happen to have in our medicine cabinet). The combinations will be:

1. Colgate Cavity Protection and Listerine Total Care Zero
2. Colgate Cavity Protection and Rite Aid Tooth Care
3. Colgate Total and Listerine Total Care Zero
4. Colgate Total and Rite Aid Tooth Care
5. Colgate Cavity Protection and no mouthwash
6. Colgate Total and no mouthwash
7. No toothpaste (brushing only) and Listerine Total Care Zero
8. No toothpaste and Rite Aid Tooth Care

Each morning we’ll then record our amount of mouth slime with one of three subjective terms:

• “Significant,” meaning there’s enough mouth slime to make you think “I have a slimy mouth”
• “Moderate,” meaning that some mouth slime is present but little enough that it could be incidental
• “None,” meaning your gums just ain’t slimy

If you’re wondering why we’re not using a more objective measuring technique, like maybe collecting and weighing our mouth slime every morning, it’s because that’s needlessly disgusting, weird, and I don’t have a precise enough scale.

Sophie and I will do the experiment in conjunction to increase sample size, but we won’t ever both try the same combination on the same night, to help reduce the effects of any environmental factors.3

I’ll report back on Tuesday with the results, or sooner if anything exciting develops, which it surely will. And depending on the outcome of this experiment, we might proceed to Phase 2, which I kind of hope we do because it would involve me ordering agar petri dishes from the Internet.

Very Important Note
If you’re reading this and know the actual cause of mouth slime or the expected results of this experiment, do not spoil the fun. However, if you have any theories you’d like to contribute or suggestions for improvements, please comment away.

Science ho!

Project Mouth Slime continues >>

1. hubba-hubba [↩]
2. Being on a limited income, we buy whichever equivalent product is cheapest based on the combination of coupons we have. [↩]
3. Though that means that if any making out occurs, it could lead to cross-contamination. We’ll have  to live with that. [↩]