Why Does Wine Only Stain Some People's Teeth?

iStock.com/yula
iStock.com/yula

Maybe getting red wine stains on your teeth would be less embarrassing if it was a universal experience. But as you may have noticed after splitting a bottle of cabernet between friends, wine doesn't have the same tinting effects on everyone. Whether vino leaves your teeth untouched or makes you look like you've been chewing on a purple Sharpie, you can give credit to your genes and hygiene habits.

A mix of components make red wine the perfect drink for staining teeth. It's acidic, which means it degrades your enamel at the microscopic level, making the surface of your teeth less even and more likely to catch pigments. Red wine contains anthocyanins, the pigment that gives wine (and the mouths of some wine-drinkers) a dusky red color, as well as tannins, which encourage those pigments to bind to your teeth. White wine also has acid and tannins (though a much lower level of tannins than reds), but without the dark pigments, drinking white wine alone won't stain your teeth.

Some wine drinkers are better equipped to handle this than others, such as those gifted with healthy, strong enamel. Enamel is the layer of minerals that protects your teeth, and it's the strongest substance in the human body. It's what makes teeth resistant to acidic foods and stains, and how much of it you have is often a product of factors beyond your control, like age and genetics. (Enamel doesn't grow back, so it wears down over a lifetime of use.)

But even if your genes are working against you, that doesn't necessarily mean you have to choose between your favorite drink and a presentable smile. You can prevent wine mouth, or at least make it look less noticeable, by practicing good oral hygiene. Teeth covered in plaque are more likely to stain, and brushing your teeth at least twice a day and flossing daily helps reduce plaque while keeping your enamel strong.

If you plan on ordering red wine at the bar you're heading to, brush your teeth beforehand: This will get rid of a lot of the plaque that would otherwise act as a magnet for pigments. Because brushing can scratch enamel in the same way that acid does, this should only be done about 30 minutes before you have your first sip of wine, and not in between glasses. Eating while you drink can help as well. By munching on a protein, you can create a sort of stain-blocking barrier for your teeth—just in case you needed an excuse to order a cheese plate with your pinot.

What you choose to drink also factors into how stained your teeth may or may not be by the end of the night. Though wines like chardonnay don't stain your teeth, they do make them more vulnerable to dark pigments, so never start off drinking white wine and move on to red. Dark wines tend to leave the darkest stains. If you absolutely must have a glass of red wine with dinner, opt for a pinot noir over a cabernet (or something lighter-bodied, in wine-speak).

Is There An International Standard Governing Scientific Naming Conventions?

iStock/Grafissimo
iStock/Grafissimo

Jelle Zijlstra:

There are lots of different systems of scientific names with different conventions or rules governing them: chemicals, genes, stars, archeological cultures, and so on. But the one I'm familiar with is the naming system for animals.

The modern naming system for animals derives from the works of the 18th-century Swedish naturalist Carl von Linné (Latinized to Carolus Linnaeus). Linnaeus introduced the system of binominal nomenclature, where animals have names composed of two parts, like Homo sapiens. Linnaeus wrote in Latin and most his names were of Latin origin, although a few were derived from Greek, like Rhinoceros for rhinos, or from other languages, like Sus babyrussa for the babirusa (from Malay).

Other people also started using Linnaeus's system, and a system of rules was developed and eventually codified into what is now called the International Code of Zoological Nomenclature (ICZN). In this case, therefore, there is indeed an international standard governing naming conventions. However, it does not put very strict requirements on the derivation of names: they are merely required to be in the Latin alphabet.

In practice a lot of well-known scientific names are derived from Greek. This is especially true for genus names: Tyrannosaurus, Macropus (kangaroos), Drosophila (fruit flies), Caenorhabditis (nematode worms), Peromyscus (deermice), and so on. Species names are more likely to be derived from Latin (e.g., T. rex, C. elegans, P. maniculatus, but Drosophila melanogaster is Greek again).

One interesting pattern I've noticed in mammals is that even when Linnaeus named the first genus in a group by a Latin name, usually most later names for related genera use Greek roots instead. For example, Linnaeus gave the name Mus to mice, and that is still the genus name for the house mouse, but most related genera use compounds of the Greek-derived root -mys (from μῦς), which also means "mouse." Similarly, bats for Linnaeus were Vespertilio, but there are many more compounds of the Greek root -nycteris (νυκτερίς); pigs are Sus, but compounds usually use Greek -choerus (χοῖρος) or -hys/-hyus (ὗς); weasels are Mustela but compounds usually use -gale or -galea (γαλέη); horses are Equus but compounds use -hippus (ἵππος).

This post originally appeared on Quora. Click here to view.

Can Soap Get Dirty?

iStock/vintagerobot
iStock/vintagerobot

When you see lovely little bars of lemon-thyme or lavender hand soaps on the rim of a sink, you know they are there to make you feel as fresh as a gardenia-scented daisy. We all know washing our hands is important, but, like washcloths and towels, can the bars of hand soap we use to clean ourselves become dirty as well?

Soaps are simply mixtures of sodium or potassium salts derived from fatty acids and alkali solutions during a process called saponification. Each soap molecule is made of a long, non-polar, hydrophobic (repelled by water) hydrocarbon chain (the "tail") capped by a polar, hydrophilic (water-soluble) "salt" head. Because soap molecules have both polar and non-polar properties, they're great emulsifiers, which means they can disperse one liquid into another.

When you wash your dirty hands with soap and water, the tails of the soap molecules are repelled by water and attracted to oils, which attract dirt. The tails cluster together and form structures called micelles, trapping the dirt and oils. The micelles are negatively charged and soluble in water, so they repel each other and remain dispersed in water—and can easily be washed away.

So, yes, soap does indeed get dirty. That's sort of how it gets your hands clean: by latching onto grease, dirt and oil more strongly than your skin does. Of course, when you're using soap, you're washing all those loose, dirt-trapping, dirty soap molecules away, but a bar of soap sitting on the bathroom counter or liquid soap in a bottle can also be contaminated with microorganisms.

This doesn't seem to be much of a problem, though. In the few studies that have been done on the matter, test subjects were given bars of soap laden with E. coli and other bacteria and instructed to wash up. None of the studies found any evidence of bacteria transfer from the soap to the subjects' hands. (It should be noted that two of these studies were conducted by Procter & Gamble and the Dial Corp., though no contradictory evidence has been found.)

Dirty soap can't clean itself, though. A contaminated bar of soap gets cleaned via the same mechanical action that helps clean you up when you wash your hands: good ol' fashioned scrubbing. The friction from rubbing your hands against the soap, as well as the flushing action of running water, removes any harmful microorganisms from both your hands and the soap and sends them down the drain.

This story was updated in 2019.

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