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By now you may have heard every trick in the skin care book: retinol, vitamin C, hyaluronic acid… these ingredients are powerful A-listers that bring out the best in your skin — but how well do they play with others?

Well, it depends on which ingredients you’re talking about. Not every ingredient is pals with each other, and some may even negate the other’s benefits.

So to maximize the most out of your bottles and droppers, here are five powerful ingredient combinations to remember. Plus, ones to absolutely avoid.

Vitamin C + ferulic acid

According to Dr. Deanne Mraz Robinson, assistant clinical professor of dermatology at Yale New Haven Hospital, ferulic acid fights free radicals to prevent and correct skin damage, and extends the life and effectiveness of vitamin C.

The most potent forms of vitamin C are often the most unstable, such as L-AA, or L-ascorbic acid, meaning that these serums are vulnerable to light, heat, and air.

However, when we combine it with ferulic acid, it helps to stabilize vitamin C so its antioxidant potency isn’t vanishing into the air.

Vitamin C + vitamin E

Vitamin E is no slouch as a skin care ingredient itself, but when paired with vitamin C, the Linus Pauling Institute at Oregon State University states that the combination is more “effective in preventing photodamage than either vitamin alone.”

Both work by negating free radical damage, but each combats different types of UV damage.

By adding vitamin C and E serums into your routine, or using products that contain both, you’re giving your skin double the antioxidant ammunition to fight damage from free radicals and more UV damage than vitamin C by itself.

Vitamin C + vitamin E + ferulic acid

By now you’re probably wondering: if vitamin C and E is good, and vitamin C and ferulic acid is too, what about a combination of all three? The answer is rhetorical: Do you love stability and antioxidants?

It’s the best of all worlds, offering triple the protective powers.

With antioxidants like vitamin C and E working in tandem to undo the damage caused by UV rays, you’re probably thinking how it makes sense to apply this combination under your sunscreen for extra UV protection. And you’d be right.

While antioxidants can’t take the place of a preventive sunscreen, they can boost your sun protection.

“Research shows that the combination of vitamins E, C, and sunscreen increases effectiveness of the sun protection,” explains Mraz Robinson. This makes it a powerful combo in the fight against both visible aging and skin cancer.

Sunscreen FAQ

The type of sunscreen you use can affect your skin care routine. Freshen up on your sunscreen knowledge here.

From acne-fighting to anti-aging, there aren’t many topical skin care ingredients that can compete with the benefits of retinoids.

“[I recommend them to] nearly all of my patients,” says Mraz Robinson. However, she also notes that retinoids, retinols, and other vitamin-A derivatives are infamous for being harsh on the skin, leading to discomfort, irritation, redness, flaking, and extreme dryness.

These side effects may be a deal breaker for some. “Many patients have a hard time tolerating them (at first) and experience excessive dryness which may discourage usage,” she explains.

So she suggests using hyaluronic acid to compliment the vitamin-A derivative. “[It’s both] hydrating and soothing, without standing in the way of the retinols ability to do its job.”

Retinol + collagen?

There are no studies looking at the effects of collagen and retinol together, as collagen molecules are too big to penetrate through the skin. But you may find benefits in collagen-like peptides, which are smaller and can help enhance the smoothness of your skin. One study found that collagen-like peptides helped with wrinkles around the eye area for women ages 40 to 62.

Just like how retinol can be too strong, Mraz Robinson warns that we should watch for “redness, inflammation, [and] excessive dryness” when combining ingredients.

The following combos require caution and monitoring:

Harmful ingredient combosSide effects
Retinoids + AHA/BHAdamages skin moisture barrier and can cause skin irritation, redness, dry skin over time; use separately and sparingly
Retinoids + vitamin Cmay cause over-exfoliation, resulting in increased skin and sun sensitivity; separate into day/night routines
Benzoyl peroxide + vitamin Cthe combination renders the effects of both useless as benzoyl peroxide will oxodize vitamin C; use on alternative days
Multiple acids (glycolic + salicylic, glycolic+ lactic, etc.)too many acids can strip the skin and damage its ability to recover
What about vitamin C and niacinamide?

The question is whether ascorbic acid (such as L-ascorbic acid) converts niacinamide to niacin, a form which can cause flushing. While it’s possible that combining these two ingredients could result in niacin forming, the concentrations and heat conditions needed to cause the reaction isn’t applicable to typical skin care use.

However, everyone’s skin is different. While the concerns about mixing the two ingredients tend to be vastly overstated within the beauty community, people with more sensitive skin will want to monitor and examine their skin more closely.

As the initial side effects of retinoids should lessen as your skin acclimates, take it slow when introducing strong ingredients to your skin care routine, or you may end up damaging your skin.

Now that you know what to use, how do you use it?

“As a general rule of thumb, apply in order of thickness, starting with the thinnest and working your way up,” explains Mraz Robinson.

She has a few caveats for specific combinations too: If using vitamin C and a physical filter sunscreen, she recommends applying the vitamin C first, then your sunscreen. When using hyaluronic acid and retinol, apply retinol first, then hyaluronic acid.

Stronger and better, together

It can be daunting to start bringing powerful ingredients into your routine, let alone mixing and matching them into even more powerful combinations.

But once you’ve got an ingredients team that’s more than the sum of its parts, your skin will get the benefits of them working smarter, harder, and with better results.

Kate M. Watts is a science enthusiast and beauty writer who dreams of finishing her coffee before it cools. Her home is overrun with old books and demanding houseplants, and she’s accepted her best life comes with a fine patina of dog hair. You can find her on Twitter.