Photo: iStock

If you’re into skin care -- or honestly, even if you’re not -- there’s a good chance you’ve heard of the infamous Korean 10+-step face care regimen. While certain products in the regimen make a lot of sense to western beauty junkies (I totally understand face cleanser!), there are some categories that probably have you scratching your head. Like essences, for example.

As I started really delving into the regimen, I was having a hard time sussing out exactly what an essence does. Confusing English translations on products from Korea, clever marketing lingo and the sheer number of products in the category all added to the challenge. My confusion peaked when I started trying to determine the difference between an essence and a serum, so I decided to consult Sarah Lee and Christine Chang, the co-founders of natural K-beauty e-commerce site Glow Recipe to help me figure it out. Come with me down the rabbit hole of concentrated, slightly gooey skin care products, won’t you?

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Toner

Photo: Missha

Before we can discuss essences, let’s talk toner. After you cleanse your face, you’re supposed to use toner, a step that’s also obviously common in western skin care regimens. A dermatologist once told me that toners were invented because soap used to be so harsh that it would raise the pH of your skin to unhealthy levels. The toner would then bring the skin’s surface pH back to normal. That’s not really an issue anymore with all the gentle face cleansers we have. Now most toners contain antioxidants or other beneficial additives and they serve as a skin prep.

According to Lee, toners in Korea provide a base layer of hydration, making the skin more amenable to what’s about to go on top. She suspects that women in the U.S. often use toning as a second cleansing step, though. (I am totally guilty of this. Many nights I’ll think I got everything off, and then when I use toner, the cotton pad is horrifyingly gunked up afterwards.) The easiest way to recognize a toner? They’re generally really watery and come in larger bottles.

Try: Missha Pore Correcting Toner, $14, available at Sokoglam

Serum

Photo: Be the Skin

OK, so your face is cleansed and toned. Technically this is when you should use an essence, but I’m going to keep you in suspense just a bit longer to talk about serums, which is a category I feel like I have a very firm grasp on. I love serums. I’m addicted. I have serum rituals and seasonal serums and I try every single one that gets sent to me.

Generally, a serum contains a few key active ingredients to address specific issues like brightening, dark spots, wrinkles, etc. The actives are usually more concentrated than what you’ll find in, say, a moisturizing cream. Serums are a bit thicker in consistency -- almost oil-like -- and usually come in a bottle that's much smaller than a toner or cleanser bottle. Often the bottles have droppers to dispense the product, though I've seen serums that are opaque and almost lotion-like, in small pump bottles.

Try: Be the Skin Botanical Pore Serum, $35, available at Peach and Lily

Essence

Photo: The Lotus

So, what the hell IS an essence then? This is going to be controversial, but here goes: An essence and a serum are essentially (haha pun!) the same thing. Mind-blowing, right? BUT. There are some important caveats to note.

According to Lee, essences traditionally were more lightweight and less concentrated than serums, and were used after a toner to add another layer of hydration before you applied serums. (SK-II's essence is a classic example of the texture.) Now, however, while you can still find the more watered-down essences (and I frequently see this type of product called an "emulsion" as well), that line is completely blurred. Serums are getting more lightweight and essences are getting thicker, and they both can contain high concentrations of active ingredients.

In fact, the very words "essence" and "serum" are nothing but marketing words now. Basically (and I'm generalizing here), western women understand "serum" and Asian women understand "essence," so now that we're all exporting our products to each other's countries, the terms essence/serum/concentrate are practically interchangeable. Lee tells me that she read a paper by a professor of cosmetics science in Korea that noted as much. It's all marketing. (A fun example in this Glow Recipe blog post: Estée Lauder's Advanced Night Repair serum is nicknamed "Brown Bottle Essence" in Korea.)

"Both essence and serums are used at the same treatment step of skincare to achieve similar results. There may be small differences in texture, but now the lines are increasingly blurry," Sokmin Yu, the head of Korean cosmetics lab Cosmax USA, explains. Ready for the real mind f*ck? He continues, "In leading beauty markets like Korea, there are many new developments in essences, which are bringing even more steps such as the pre-essence and post-essence to the skincare routine." Pre-essence? Oh, please no.

This is probably also a good time to mention treatment toners, also called essence lotions or essence toners. These have a consistency that people more traditionally associate with an essence -- thinner but with a bit of body. Clinique's recently launched version is a perfect example. They can replace a traditional toner, but have more hydrating oomph. (This one by Whamisa is beautiful. The posh French skin care brand Sisley also has a luxe version, called Sisleya Essential Skin Care Lotion, launching in March.) They fall somewhere between a toner and a serum on the gooey scale.

Try: The Lotus Essence, $43, available at Glow Recipe

Ampoule

Photo: Lee Jiham

A quick word on ampoules, because they're in the same family as essences and serums. An ampoule is a supercharged serum with higher concentrations of active ingredients that you're meant to use for a finite amount of time as a booster or when you're having a skin crisis of some sort. Chang recommends using them before your essence or serum. Ampoules usually come in smaller bottles with droppers.

Try: LJH Vita Propolis Ampoule, $38, available at Glow Recipe (I've been loving this for extra hydration and glowiness during a very stressful week.)

The Bottom Line

As long as women are interested in applying 27 different products, companies will be happy to introduce them. But don't panic.

• First, figure out what your skin needs and choose products with ingredients that fit the bill. Don't get caught up in whether it's a serum or an essence. Ignore everything on the label except the ingredients.

• After you figure out the right ingredients for your skin issues, choose a texture that suits your skin type and your sensibility. Try out different textures to see what you like. Don't worry about following some cookbook notion of what your skin care regimen should look like. It should constantly evolve, depending on what your skin needs.

• Remember that skin care products exist on a continuum. You can always find something more concentrated or more watery or richer or lighter.

• Finally, no matter which or how many products you use, the general rule-of-thumb is to apply the most watery product first and the thickest, richest one last.

There. Clear as an essence.