It, regrettably, took years of baking in the sun every summer to finally heed our dermatologists’ advice about wearing sunscreen daily. And now that we’re older (and wiser), and know how important it is to apply SPF before leaving the house, it’s time to take an extra step to protect ourselves from the sun’s damaging rays.

Yes, you can do more than just rub in broad-spectrum sunscreen — in fact, derms say that using vitamin C under your SPF is one of the best ways to prevent premature skin aging and reduce your risk of skin cancer.

But yet another step in my skincare routine? You may be thinking. This one’s a non-negotiable and recommended for nearly all skin types, according to dermatologists. So you’ll want the lowdown on how to apply vitamin C with your sunscreen.

Why you should layer vitamin C under your sunscreen

Both sunscreen and vitamin C help shield your skin from the sun’s UV rays in different ways. And the benefits are compounded when you combine them.

Your SPF works by absorbing or reflecting UV rays. But no sunscreen is 100 percent effective at blocking UV rays, says Elyse Love, MD, a New York City-based board-certified dermatologist. “For example, SPF 30 applied appropriately blocks approximately 97 percent of sun rays, meaning that 3 percent of sun rays make it through the protection and cause sun damage through oxidative stress,” she says. “This oxidative stress can lead to DNA damage (skin cancer), increased pigmentation (dark spots), dilated vessels (redness), and loss of collagen (fine lines and wrinkles).”

And that’s where vitamin C comes in. Because it’s an antioxidant, it can help neutralize all that oxidative stress, keeping your skin supple and protected. In fact, researchers found that sunscreens block only 55 percent of the free radicals produced by UV exposure, and by adding a vitamin C to the mix, they were able to reduce sunburn by an additional 50 percent, according to a study in the Indian Dermatology Online Journal.

What type of vitamin C should you use?

Vitamin C concentrations can be confusing, as the molecule comes in many forms with various levels of stability, activity, and potential irritation, Dr. Love says. “L-ascorbic acid is the active form of vitamin C, and studies show that results are proportional to concentration, with a max concentration of 20 percent being absorbed by the skin.”

Dr. Love recommends folks new to vitamin C start with 10 percent l-ascorbic acid—which, FYI, is the concentration that was shown to fend off a significant amount of free radicals in the Indian Dermatology Online Journal study—and slowly build their way up to 20 percent l-ascorbic acid as tolerated.

And bonus points if you can find a product that contains vitamin E, as the ingredient has been shown to increase the antioxidant benefits of vitamin C, says Dr. Love. “Those with dry and/or sensitive skin should [get] vitamin C products with vitamin E as vitamin E is soothing to the skin and can decrease some of the potential irritation with vitamin C,” Dr. Love says.

Not sure which C to buy? Dr. Love says First Aid Beauty 10% Vitamin C Brightening Serum ($50) is a great entry-level option because it’s non-comedogenic and contains moisturizing vitamin E and squalane. If you’ve got sensitive, rosacea-prone skin, try Skinbetter Alto Defense ($165), which combines vitamins C and E (and 17 other antioxidants) to help decrease skin sensitivity and redness. SkinCeuticals C E Ferulic ($182) also contains both antioxidants to help fend off free radical. For something at a drugstore price point, L’Oréal Paris Revitalift 12% Vitamin C + E + Salicylic ($26) is a great option, particularly for those with oily or acne-prone skin thanks to its inclusion of salicylic acid.

How to apply

Correct application is the key to success here.  Vitamin C typically comes in the form of a serum, so it should be applied before your moisturizer — in other words, C comes first.

After cleansing your skin, apply your vitamin C (and any other serums you use in order of lightest to thickest), then your moisturizer (if separate from SPF), and lastly your SPF. “Sunscreen should always be applied as the last step of the skincare routine,” Dr. Love says. “And there is no need to wait in between applications.”

As for SPFs, always look for a product that boasts “broad-spectrum,” which means it protects against both UVA and UVB rays—shop some of our award-winning favorites here.

Another thing to note: While you may find products that contain both vitamin C and SPF, it might be best to purchase the active separately from your sunscreen. “Most vitamin C-dedicated serums will contain a higher concentration of vitamin C than a vitamin C-infused sunscreen or a vitamin C-infused moisturizer,” Dr. Love says.

So as long as you slather on your vitamin C serum before your sunscreen, consider yourself doing the most when it comes to sun protection. And being extra is basically always in your best interest.