This year, more of the country will be outside for longer stretches than at almost any other point in summer, and for anyone using retinol, that shift changes the math on their skincare routine. Retinol is a vitamin A derivative that speeds up cell turnover, softens fine lines, and triggers new collagen production, changes that take weeks or months to show up, according to a 2025 review in the International Journal of Cosmetic Science. The same review explains that ultraviolet exposure breaks down existing collagen and creates new pigmentation and texture damage, which means the two forces, one building and one dismantling, are often happening on the same face at the same time.

Sunscreen is the variable that decides which one wins. Real-world use tends to fall short of what a bottle’s SPF number promises. A clinical study published in the Journal of Investigative Dermatology found that people who applied sunscreen at their usual amount, rather than the thicker layer used in lab testing, got less protection than the labeled SPF, and that closing that gap required both a thicker application and reapplying more often than most people do on their own.

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That gap matters more for retinol users specifically. Retinol thins the outermost layer of dead skin cells to reveal newer skin underneath, and that newer skin has less natural buffer against UV light. Skipping sunscreen on a day at the beach, or underapplying it on an ordinary Tuesday, does not just add a normal amount of sun exposure. It adds exposure to skin that is already more vulnerable than it was before starting retinol.

Paula Brezavscek sees this constantly at her Coral Gables, Florida practice, where she works as a board-certified physician associate specializing in cosmetic dermatology. “If you’re using retinol without wearing sunscreen every day, you’re working against the benefits you’re trying to achieve,” she explains. “I always tell my patients that sunscreen is what protects the results that retinol helps create.”

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There’s a rumor that layering sunscreen over retinol or vitamin C cancels the ingredients out, like they’re elbowing each other for space. Brezavscek says that’s just not true. “Sunscreen doesn’t make retinol or vitamin C less effective,” she notes. “In fact, they work really well together. Vitamin C helps defend against free radical damage, retinol improves skin quality, and sunscreen protects your skin from future UV damage. Each product has its own role, and together they create a much stronger skincare routine.”

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The mistakes Brezavscek actually sees in her patients aren’t about ingredients. They’re about habits. “The biggest mistake is only wearing sunscreen when they’re going to the beach or spending the day outside,” she points out. “Another common mistake is not applying enough. Most people use much less than what’s needed to get the SPF protection listed on the bottle.”

Most people don’t apply enough moisturizer or foundation to get real SPF benefits according to Brezavscek. “If you’re using retinol or having treatments like chemical peels or lasers, I recommend using a separate broad-spectrum SPF 30 or higher every morning,” she describes. “Makeup with SPF is a nice bonus but it shouldn’t be your primary sun protection.”

How to Protect Your Anti-Aging Skincare Investment This Summer

Part of why sunscreen gets skipped is that the consequences of skipping it are not immediate. Retinol users can see results in the mirror within weeks. Sun damage takes far longer to announce itself, and that lag makes it easy to underestimate. “Many people think they’ll notice the effects right away if they skip sunscreen, but that’s usually not what happens,” Brezavscek says. “Sun damage builds over time. Every day of unprotected exposure contributes to collagen loss, pigmentation, and premature aging.” That gradual timeline is also why skin can keep changing years after a routine has stayed the same, since the damage being addressed today was often set in motion long before it became visible.

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For anyone who has spent real money on retinol, peels, or brightening treatments, your sunscreen habit is not a side note to that investment. “Many of the treatments and skincare products we use are designed to repair existing sun damage and improve skin quality,” Brezavscek explains. “If you’re not consistently protecting your skin from UV exposure, you’re creating new damage while trying to fix the old damage.”

Your fix this weekend is not complicated. A broad-spectrum SPF 30 or higher, and apply a nickel-sized amount to your face every two-ish hours outside.

Paula Brezavscek is a board-certified physician associate specializing in cosmetic dermatology.