The 5 Most Common Skincare Ingredients—and How to Actually Use Them



In the last decade, the skincare industry has gotten really…complicated. Remember the days of the iconic three-step (three!) cleansing, toning and moisturizing system? Maybe an Oxy pad haphazardly swiped across a forehead here and there, during particularly trying periods. It was a simpler time.

These days, thanks in large part to social media and the limitless portal of information that is the internet, it appears as though the entire online skincare community has adopted the jargon and vocabulary of a seasoned dermatologist. Ten-step routines, filled with an array of active ingredients, have become the norm. Impressive but, yet again, complicated.

But whether you’re a skincare minimalist or maximalist, swear by the bible that is Reddit’s  or prefer to just wing it on your own, there are certain ingredients that make up a common ground—regardless of skin philosophy. They’re the ones that are found in the bulk of the products on the market, have been studied thoroughly over the years and are proven to, you know, work.

We tapped the pros to find out, once and for all, how (and when and why) to use the five basic skincare ingredients that you’ll come across in your skincare regimen, no matter how simple or complex it may be.

Hyaluronic Acid

What is it? 

There’s no better place to kick off skincare school than with the crème de la crème of hydration: hyaluronic acid. The substance, which is naturally found in our skin, is a humectant (meaning it draws in moisture from its surroundings) and can hold up to 1,000 times its weight in water.

What does it do?

“It replenishes the amounts [of naturally occurring hyaluronic acid in your skin] that have been lost due to photoaging and sun damage to allow for a firmer, youthful appearance,” says Jessica Burman, Founder of Cocoon Apothecary.“It’s known for increasing hydration levels to plump up fine lines and heal dry, flaky skin.”

It can also be used in injectable form, like Restylane Skinboosters, says Dr. Lisa Kellett, dermatologist at DLK on Avenue. Those “results can last up to one year because of the direct delivery into the skin.”


What is it?

A form of synthetic vitamin A, retinol is considered the gold standard when it comes to over-the-counter anti-aging ingredients. It speeds up the process of sloughing off dead skin cells, so it’s useful if you’re looking to target anything from fine lines to dark spots, as well as other signs of aging.

How should retinol be used?

This one’s a bit of a doozy. “Typically the skin needs time to acclimate to products that contain retinol,” explains Ursula Diaz, co-founder of skincare company Honor MD. “To avoid common irritation associated with products that contain retinol (like redness and dryness) we recommend patients start using it one to two times per week (at night, since it can cause sun sensitivity) and to gradually increase usage as tolerated. The goal should be every night or every night.”

Alpha hydroxy Acids (AHAs)

What are they?

Alpha hydroxy acids (AHAs) are a class of chemical exfoliators that dissolve the bonds between skin cells, allowing you to slough away the dead skin cells that sit on top of your skin—gross, we know. The most well-known, and well-researched, of the bunch are lactic acid and glycolic acid, which are typically derived from milk and sugarcane, respectively, though vegans shouldn’t fret, since most lactic acid found in skincare these days is synthetically derived.

How should they be used?

Nighttime use is best, as they can be irritating—especially glycolic acid, the less gentle of the two. Dr. Kellett advises to opt for a serum over a mask or cleanser, both of which have less time on skin to work their exfoliating magic. And while the ideal percentage of glycolic acid is highly dependent upon your tolerance and skin type, when it comes to lactic acid, you’ll want to look for 5 to 10% for topicals, and 10 to 20% in peels, she says.

Vitamin C 

What is it?

Easily the most well-known antioxidant in skincare, vitamin C (also known as L-ascorbic acid) is an absolute must for brightening your overall skin tone, lightening acne scars and dark spots and providing skin with a shield-like layer of protection from pollution and particulate matter (tiny particles in the air like pollen and dust). Fun fact: Vitamin C is actually the number-two rising Google search for all face care topics worldwide (right behind retinol). So if you haven’t already, it’s time to get acquainted with this powerhouse.

How should it be used? 

Once daily is enough, says Dr. Kellett, but whether you use it in the morning or at night depends on what other products and ingredients you’re using. For example, you definitely won’t want an oil-based cleanser to block your water-based vitamin C serum from absorbing into skin—a good rule of thumb when using any combination of oil-based and water-based products, of course, but especially with (usually) pricey vitamin C serums—you don’t want to waste any of this gold.

It’s also a good idea to avoid using vitamin C at the same time as exfoliants like retinol, BHAs and AHAs, which can sometimes lead to redness, flaking and irritation, and is why most people tend to use a vitamin C serum in the morning, and other chemical exfoliants in the evening. Bonus: Layering a vitamin C serum under your sunscreen during the day adds extra protection from the sun’s UV rays, pollution, dust and more. Remember that shielding ability we mentioned above? Trust us—you want to take advantage of it.

Salicylic Acid 

What is it? 

“Salicylic acid is a chemical exfoliant that is sourced from willow tree bark,” explains Burman. The beta-hydroxy acid is especially useful for those with oily or acne-prone skin, as its small molecular size allows it to get deep into the skin and dissolve the pore-clogging debris that lead to acne, blackheads and whiteheads.

How should it be used?

It can be used daily, but because it is a chemical exfoliant and can potentially be irritating, Dr. Kellett suggests avoiding using it with other keratolytics [like trichloroacetic acid and Allantoin] and alpha hydroxy acids (AHAs like glycolic and lactic acid).


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