You Might Be Applying Your Face Serums Incorrectly, According To Derms

Raise your hand if know what a serum is, but can’t quite put it into words. Like, maybe you’re aware it’s the step after toning and before moisturizing, and you know that serums are typically pretty potent, but if your science teacher called on you to explain serums to the entire class in some anxiety-nightmare scenario, you’d be left stuttering. OK, yup, that’s what I thought — so here’s a lesson on how to apply facial serums, once and for all.

Read more: How To Apply Face Oil Properly, Because You Definitely Need It In Your Routine

Let’s start with the basics: Serums are lightweight, often watery gels or lotions featuring small, fast-absorbing molecules of active, “problem-solving” skincare ingredients. They have one job, and that’s to deliver said active ingredients deep into the skin and thus, produce actual, visible results. Serums are “extras” — you don’t need to use one (unlike, say, some sort of cleanser, which is a non-negotiable). But are they nice to have? Sure, especially if you’re dealing with an issue like hyperpigmentation (vitamin C serum to the rescue!) or dehydration (derms love hyaluronic acid formulas).

That sounds simple enough… until you consider the sheer amount of serums on the market, all of which have different actives, and some of which are (bafflingly) oil-based. Confused? Consult the guide ahead for the facts on all your serum FAQs.

Serum Application Tip: It Goes Before Moisturizer...

“I recommend applying products from thinnest to thickest,” Dr. Devika Icecreamwala, M.D., F.A.A.D, a dermatologist with Icecreamwala Dermatology, tells The Zoe Report. “Serums are typically thinner than moisturizers” — remember, they’re usually watery — “so I recommend moisturizer being applied after serum.”

Serum Application Tip: ... But It's Not The First Step

Depending on how detailed your skincare routine is, a serum could be your first step after cleansing. But if you love to layer on toners, face mists, and essences, those all go before the serum. Basically, anything that’s a pure liquid belongs in your routine pre-serum, and anything thicker is a post-serum product.

Serum Application Tip: There’s A Reason Why They're Usually Water-Based...

“Water serves as a delivery vehicle for the ingredients that are in the serum,” Ron Robinson, a cosmetic chemist and founder of BeautyStat, tells The Zoe Report. “Once you apply the serum, the water evaporates, leaving the other ingredients on the skin to do their job.”

Serum Application Tip: ... Which Is Why You Don’t Want To Skip Moisturizer

Because water evaporates quickly, applying a serum and only a serum could, theoretically, dry out your skin. You want to “lock in” some of that hydration, along with those active ingredients, by following up with a moisturizer ASAP.

Serum Application Tip: Silicone-Based Formulas Present A Problem

A serum will typically have a low molecular weight, all the better to absorb into the skin. Silicone, however, is a very large molecule, and is unable to penetrate the skin barrier (which is why it’s known for leaving behind a slippery, glowy, “Saran Wrap”-like coating). If the active ingredients in your serum are ensconced in silicone, cosmetic chemists say they'll probably remain trapped on the surface — and you won’t see the results you want.

Serum Application Tip: Some Are Oil-Based… & Therefore, Not Technically Serums?

A lot of “serums” on the market are oil-based, like the famed Vintner’s Daughter Active Botanical Serum. In the case of that particular product, the label “serum” makes sense, since the formula is highly active. On the other hand, it’s thicker than a traditional moisturizer, so it doesn't belong in the traditional “serum spot” of your routine. Perhaps New York City-based aesthetician Aida Bicaj said it best when she told Into The Gloss, “The oil-based serums go on top of the moisturizer because they have a bigger molecule. They're supposed to keep the cream and whatever you put underneath moist during the entire day.” So, sure, go ahead and call your oil-based serum a serum... just make sure to use it like an oil.

Serum Application Tip: The Best Ingredients For Acne-Prone Skin Are...

“Look for a serum with salicylic acid or an ingredient from which salicylic acid is derived, like willow bark extract,” Dr. Sejal Shah, M.D., F.A.A.D., a dermatologist with SmarterSkin Dermatology, tells TZR. “Salicylic acid helps exfoliate skin and unclog pores. One example is Juice Beauty Blemish Clearing Serum, which contains willow bark extract plus antioxidants, anti-inflammatory ingredients, and hydrating ingredients.”

Serum Application Tip: The Best Ingredients For Mature Skin Are...

“Mature skin concerns include both signs of aging and dryness,” Dr. Shah says, recommending a vitamin C serum. “Vitamin C is a powerful antioxidant that has been shown to boost collagen synthesis, improve the appearance of fine lines and wrinkles, brighten skin, and reduce hyperpigmentation.”

Serum Application Tip: The Best Ingredients For Oily Skin Are...

“For oily skin, I like serums that have oil-balancing ingredients and a mattifying moisturizer,” Dr. Shah says. “For example, Odacite's Gr+G Serum, which contains grapeseed oil to balance sebum production and grapefruit oil which acts as an astringent.”

Serum Application Tip: The Best Ingredients For Dry Skin Are...

“Hyaluronic acid acts as a humectant and pulls water into the skin,” Dr. Shah says, making it a top pick for dry skin — but be careful here. Hyaluronic acid is known for holding 1,000 times its weight in water, but you have to ask: Where is that water coming from? If you’re in a dry climate and there’s not a lot of moisture in the air, hyaluronic acid will pull water from within your skin and drag it up to the surface, having the opposite of the intended effect. If you do choose to use hyaluronic acid serums, make sure you immediately follow up with a water-based moisturizer to supply those hyaluronic acid molecules with all the water they crave. Another option, says Dr. Shah, is niacinamide, which works to restore the skin's natural moisture barrier. (Ghost Democracy's new Floodgate Hyaluronic Acid Serum has both.)

... So In That Case, You Make Want To Opt For An Oil-Based Serum, After All

“Less humidity and colder temperatures can make the skin drier,” Dr. Melanie Palm, M.D., M.B.A., a board-certified dermatologist and cosmetic surgeon with Art of Skin, tells TZR. “For this reason, dermatologists may recommend switching patients to heavier [serums] during colder weather, in order to preserve the skin barrier and decrease skin irritation due to the elements.”