The sun's dark side, quantified: It is behind 80 percent of wrinkles and spots and is the primary cause of skin cancer. How can you enjoy a minute outdoors knowing that? The same way dermatologists do—with the clever protection methods they've developed to save their own skin.

They've read (or written) all the studies. They've researched and tested countless products. And they witness, daily, the effects of too much UV exposure in their patients. But in one very important way, dermatologists are just like us! They still go out into the world and worry about the health of their own skin. So what do they actually do with this knowledge? How do they boil it down into doable steps for everyday mornings and beachday activities? We polled 23 top derms about the educated tweaks they make to a typical SPF routine. This full-access guide to protecting your skin like an M.D. starts with, of all things, toothpaste.

Giving 'screen a front-and-center spot on the bathroom sink serves as the greatest reminder to put it on every morning. "I've been doing this for years," says Boston dermatologist Ranella Hirsch, M.D. The habit is backed by science: A recent study showed that participants who stored SPF by toothpaste had a 20 percent increase in use compared with the group who kept it elsewhere.

Related: The Best Face Masks For Your Skin, According To Dermatologists

When sunscreens are tested in the lab under perfect conditions, scientists determine their SPF based on using a superthick (some say impractical) amount to cover skin. "Studies have shown that people tend to underapply sunscreen, and that it wears off over the course of two hours," says dermatologist Macrene Alexiades, M.D., Ph.D., an associate clinical professor of dermatology at Yale University School of Medicine. "This means that if you start with an SPF of 100 and underapply by half, you're starting with the equivalent of an SPF 50, which then deteriorates to about an SPF of 30 or 15 by the two-hour mark." All the more reason she opts for Neutrogena Age Shield Face SPF 110 ($11, amazon.com) whenever she's going to be outdoors all day.

Every single derm we polled said the minimum they reach for on regular days is SPF 30—but that number, again, is subject to some sun algebra. "The SPF corresponds to a percent blockage of rays. So if you live in New York City, the difference between blocking 97 percent with SPF 30 versus nearly 99 percent with SPF 100 may not be a big deal—but if you live in Florida, where the rays are a lot more direct, using an SPF higher than 30 does make a difference because every percentage point of additional blockage means a lot less skin cancer risk," Alexiades says.

Watch a dermatologist explain the best way to protect your skin from the sun:

preview for Sun Protection

These doctors spend all day examining people from head to toe—and they've seen the places where skin cancer pops up and wrinkles set in. In addition to the tops of and behind ears, backs of hands, knees, and tops of feet, there are three other places that seem obvious but we regularly forget: "I see a lot of that plucked-chicken-skin effect on the sides of people's necks. Our chins protect the center of the neck a bit from the sun, but not the sides. I always make sure I've applied my facial SPF down and around my whole neck," says dermatologist Doris Day, M.D., a clinical associate professor of dermatology at the New York University Langone Medical Center.

The other often-overlooked areas are between your toes and along the hairline. "I witness a ton of brown spots in front of the ears as well as on the top of the forehead, so I start my facial sunscreen at the periphery, then get more product if I need to once I reach my nose," says Day. Others dust a powder SPF, like Colorescience Sunforgettable SPF 50 ($64, colorescience.com), through those face-framing baby hairs if they don't want to gunk them up with a cream.

Most derms agree that the standard measurements recommended for sunscreen—a teaspoon for the face, a shot glass for the body—are completely lost on everyone (including themselves—except for the one derm we spoke to who actually measures it out!). Instead, nearly all of them apply in layers to get sufficient coverage—and rub in different directions on round two. "This ensures I haven't missed a spot," says dermatologist Vivian Bucay, M.D., founder of the Bucay Center for Dermatology and Aesthetics in San Antonio. Oh, and they do this while naked: "Doing so avoids burns along the edges of a bathing suit or clothes, which I often see in patients," says dermatologist Emmy Graber, M.D., president of The Dermatology Institute of Boston. Still unsure if you've applied enough? Our derms insist you're properly covered only when you can see the results glistening on your skin.

Related: 5 Places You Should Think Twice About Tweezing

But first, coffee: Dermatologist Whitney Bowe, M.D., a clinical assistant professor of dermatology at the Icahn School of Medicine at Mount Sinai in New York City, upped her java intake from eight to 12 ounces after reading a recent study that showed more coffee equals a lower risk of developing malignant melanoma.

As for antioxidants, they're a safety net, protecting against free radicals that slip through the cracks of your SPF—which one study showed can be up to 45 percent! "There's research that says the combination of ferulic acid with vitamins C and E can increase your sunscreen's SPF by eight," says dermatologist Tina Alster, M.D., a clinical professor of dermatology at Georgetown University Medical Center, who layers SkinCeuticals C E Ferulic serum ($145, amazon.com) under her sunscreen.

If a two-step routine is one step too many, dermatologist Diane Berson, M.D., an associate clinical professor of dermatology at Weill Medical College of Cornell University, loves the new wave of sunscreens with strong antioxidants built in. Olay Complete All Day Moisturizer SPF 30 Sensitive ($17, amazon.com) is a favorite. Both Day and Alexiades also follow antioxidant-rich Mediterranean diets to help protect against UV damage from the inside. (Hit the reset button—and burn fat like crazy with The Body Clock Diet!)

"Anything super shiny can act like a magnifier and enhance the penetration of sunlight—I've seen lots of patients wear lip gloss outside and get so sunburned their lips were puffy," says Graber, adding that lower-lip skin cancers are common and, in her experience, often likely to spread. During the day, the pros prefer lip balm with SPF, like Coola Sport Liplux SPF 30 ($12, amazon.com).

And don't be shy about reapplying—it's the first place sunscreen disappears because we're constantly licking our lips, eating, and drinking. Or try this move from dermatologist Amy Wechsler, M.D., an assistant clinical professor of dermatology at SUNY Downstate Medical Center: "I close my mouth and do a pass over my lips when I put on my regular sunscreen to cover them with the formula."

Studies demonstrate that the UV exposure we get through car windows can do a lot of damage—a famous one looked at the (shockingly) accelerated weathering on the left side of the face of a truck driver; another showed an increase in skin cancers on Americans' left side of the face and left arm. "I see this in my practice—it's pretty incredible to be treating 10 precancers on one side and zero on the other all because of extra sun exposure," says dermatologist Ellen Marmur, M.D., an associate clinical professor of dermatology at Icahn School of Medicine at Mount Sinai in New York City.

In fact, one recent study published in JAMA Ophthalmology showed side windows allow an average of 25 percent more UVA rays, the type associated with skin cancer and the visible signs of skin aging, into the car than windshields, which are built in a way that blocks out about 95 percent of UVA. All windows of a car effectively block out UVB rays, the type associated with skin cancer and burns.

Related: Could Frequent Flying Pose a Melanoma Risk?

The derms we spoke to who spend quality time on the road insist on adding UVA-protection films to their car windows (since the law varies by state on how dark you can tint your windows, check drivinglaws.aaa.com). "I have the Llumar Air 80 ceramic window tints, which also reduce heat buildup in the car," says dermatologist Arielle Kauvar, M.D., a clinical professor of dermatology at New York University School of Medicine, whose commute clocks in at two hours daily.

If their windows don't have the additional exterior protection, they stash powder sunscreens, like the above-mentioned Colorescience one ($64, colorescience.com), in their glove compartments—it won't break down in a sweltering car—and apply over any exposed skin before they start the engine. "Don't forget your hands," says San Diego dermatologist Kimberly Butterwick, M.D. "Women, especially, get a ton of age spots there—I think they tend to keep their hands at the top of the wheel."

This article originally appeared in the May 2017 issue of Women's Health. For more great advice, pick up a copy of the issue on newsstands now!