If you sweat profusely (think outdoor exercise or what can happen on a really humid day) or if you wash or sanitize your hands, swim, or get wet, you must reapply your sunscreen regardless of the SPF number on the product. If the sunscreen is labeled “very water resistant,” you get about 80 minutes of protection while perspiring or swimming. If the label states “water-resistant,” you get only about 40 minutes of protection if you get wet. [48] But don’t forget, even if you use those types of sunscreens, you’ll be rubbing them off when toweling dry, so in that scenario, be sure to reapply.
As you’ve seen, the rules for applying and reapplying sunscreen if you’re getting wet or sweating are entirely different from the rules if you stay dry and spend only limited time outside.
It’s also critical to understand that being inside doesn’t mean your skin is protected from sun exposure. If you’re sitting next to a window, it’s highly unlikely you’ll get sunburned because almost all windows protect you from UVB rays, the rays that cause burning. However, unless the window has special UVA shielding, your skin will NOT be protected from the sun’s UVA rays because these rays penetrate windows. [49] This is one of the factors you must take into consideration when deciding how often to reapply your sunscreen, or be sure you’re wearing sunscreens with higher SPF. You can also consider the following:
Find out if the windows filter both UVB and UVA rays.
Use blinds to control the amount of daylight that enters your work space.
Add a UV-filtering film to your office window; these films are sold in most major hardware stores and are easy to apply.
Common Sunscreen Questions, Answered!
What does “liberal” application really mean? As we mentioned above, there are varying measurements given to help you figure out how much sunscreen to apply. The standard often cited by dermatologists is to use an ounce of sunscreen (what would fill a standard shot glass) for head-to-toe coverage.[8,50] But, although well-meaning, this is just an impractical and somewhat illogical guideline.
The shot glass rule would apply only if you’re a thin, petite person wearing minimal clothing, such as a bathing suit for the beach or a tank top and shorts. If you’re a tall, heavyset person wearing minimal clothing, a shot glass amount literally won’t cover it. The total surface area exposed is what matters and a shot glass may or may not be enough. Following our rule of applying a layer of sunscreen you can see and then smoothing it over skin to let it absorb should work well.
Keep in mind that the more skin that’s covered by opaque clothing with a tight weave that doesn’t let sunlight through, the less sunscreen you need to apply because the clothing also provides protection. Don’t count on your clothing alone, however, especially for long days outside; for that, look to special sunscreen clothing companies, such as the Sun Precautions and Coolibar brands, which sell their products online and in some sporting goods stores.
Another option we recommend for achieving liberal application on your face is to layer sunscreens. For example, apply an amount of your daytime moisturizer with SPF 30 or greater that feels comfortable, and then follow it with a foundation rated SPF 15 or greater and set that with a pressed powder that provides additional sun protection. Voilà, you get great sun protection without skin feeling too slick or heavy from a liberal application of sunscreen.
Keep in mind that layering sunscreens is not additive; for example, applying an SPF 15 and an SPF 30 doesn’t net an SPF 45. However, adding sunscreen ingredients by layering different SPF-rated products absolutely helps boost protection, just how much more isn’t exact. Applying more sunscreen ingredients to your skin is how chemists formulate sunscreens to achieve higher SPF ratings—they add more active sunscreen ingredients! Now that’s sun-smart behavior!
When should you apply sunscreen? Every day, as the last step in your skincare routine. The vast majority of medical experts and skin researchers agree: Sunscreen is always, always, the final step in your skincare routine. [47,51] Any skincare product applied over a sunscreen dilutes the sunscreen, reducing its effectiveness to some degree. So, if you apply a moisturizer or a serum over your sunscreen, the amount of protection you get is reduced, and that’s a serious problem.
With the exception of a small minority of naysayers, the above guidelines are universally agreed on as the correct way to use sunscreens. Forgoing this important step is a disservice to the health and appearance of your skin, but, of course, this is your decision to make.
Do you need moisturizer AND sunscreen during the day? Typically, no. That’s because most sunscreens are formulated in a moisturizing base. Plus, the best ones also contain other beneficial ingredients, so most people can skip applying “regular” moisturizer during the day—your sunscreen product should provide enough moisture, so there’s no need to layer moisturizer underneath. Instead, consider applying an antioxidant-rich serum before your sunscreen or a booster (sometimes labeled “essence”) to increase skin’s environmental defenses. Research has demonstrated that sunscreens work better and provide even more benefit when paired with an abundant amount and variety of antioxidants. [13,14]
We’re occasionally asked if it’s necessary to use a “regular sunscreen” on top of a daytime moisturizer with SPF. A sunscreen is a sunscreen; whether labeled a “daytime moisturizer” or a “sunscreen,” it will provide you with the same UV protection benefits as long as it is rated SPF 30 or greater and contains active ingredients that, singly or together, provide broad-spectrum protection.
The primary difference between a daytime moisturizer with an SPF rating and a larger-sized product labeled a sunscreen is that the daytime moisturizer with sunscreen typically also contains larger amounts of other beneficial ingredients (that is, antioxidants and cell-communicating ingredients) than a “regular” sunscreen formula. Thus, a facial moisturizer with SPF should pack a greater anti-aging punch than that giant bottle of sunscreen you keep in your beach bag, even though their SPF ratings are identical. But, if all you’re after is protection from UV light, then a regular sunscreen can also be applied to the face, and, of course, doing so saves money, too.
What about the recommendation to wait after application before venturing outside? Synthetic sunscreen actives (common examples include avobenzone, octinoxate, and oxybenzone) should really be applied 20 minutes before exposing your skin to daylight because they need time to “get situated” in the uppermost layers of skin before they can provide optimal protection. [9,52]
On the other hand, the mineral sunscreen actives—titanium dioxide and zinc oxide—provide immediate sun protection, so it’s not necessary to wait if your sunscreen contains them. [9,52] That’s why we recommend using a mineral sunscreen for your hands when you’re outdoors, and always reapplying after washing or sanitizing them.
We’re occasionally asked whether it’s OK to use makeup that contains mineral sunscreen actives on top of a sunscreen that contains synthetic sunscreen actives. This is fine—the manner in which today’s sunscreen actives are encapsulated, coated, and stabilized makes this a worry-free way to apply your makeup and sunscreen formulas. In fact, many sun-care experts recommend layering like this to get maximum protection!
What about applying foundation (one that doesn’t contain sunscreen) over the sunscreen you’ve just applied? As mentioned above, this will dilute the sunscreen and reduce its effectiveness somewhat, but there are steps you can take to minimize this effect:
Wait 3–5 minutes for the sunscreen to set before applying the foundation.
Make sure you apply in smooth, downward motions; do not use a rubbing or back-and-forth motion or apply the foundation with a damp sponge.
Do not use excess pressure, regardless of the application tool you prefer.
Use a dry (not damp) foundation sponge or brush rather than your fingers.
If