How to Apply Sunscreen
Do You Need to Reapply Sunscreen Every Few Hours?
One of the most common questions we're asked is whether or not the sunscreen applied in the morning is still working in the late afternoon, following a day at the office or at school. Sunscreen actives break down in response to direct exposure to daylight, not by the passage of time. So, on an average day, your morning application of sunscreen is still going to provide some UV protection on your way home. This assumes you applied a sufficient amount in the morning, and that you have a schedule and job that keep you indoors and out of the sun for the majority of the day.
If you spend the majority of your day outdoors, then the recommendation is to reapply every two hours, particularly if you're perspiring or swimming.
This recommendation to reapply sunscreen every few hours is based on the following:
- Most people don't apply sunscreen liberally, and if you don't, you won't get the SPF protection rating shown on the label. If you're one of those people who doesn't apply sunscreen liberally, then the apply-every-two-hours guideline makes sense: Reapplying every few hours after direct daylight exposure will result in liberal application because of the extra layers of sunscreen you are putting on.
- If you sweat profusely (think outdoor exercise), wash 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. So, the set of rules for applying and reapplying sunscreen if you're getting wet or sweating is entirely different from the set of rules if you stay dry.
What if You Sit Next to a Window Indoors?
Sitting next to a window that's not made of special UV-shielding glass that protects against UVA rays as well as UVB rays (almost all windows protect you from UVB rays, which is why you don't get sunburned indoors) can mean you need to reapply your sunscreen more often. However, it's much easier to:
- Check with your building manager to find out if the windows filter UVA and UVB 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.
How Much Is Enough Sunscreen?
So, what does "liberal application" really mean? The standard rule accepted by most dermatologists is to use an ounce of sunscreen (what would fill a standard shot glass) for head-to-toe coverage—that amount will ensure you aren't skimping on how much you use.
The shot-glass rule assumes you're wearing minimal clothing, such as a bathing suit for the beach or just a tank top and shorts. The more of your skin that's covered by opaque clothing whose fabric has a tight weave, the less sunscreen you need to apply because the clothing provides its own protection. However, don't count on your clothing alone for long days in direct sunlight; for that, look to special sunscreen clothing companies such as the Sun Precautions and Coolibar brands, sold online.
For face and neck application (as in your daytime moisturizer with SPF), "liberal" application is a nickel- to quarter-size amount (approximately ¼ teaspoon) for the face, the same amount for the neck, and, if exposed, the same amount for the chest area. This amount, for the face and the neck, is the amount generally recommended by physicians.
You might need to experiment based on the product's texture and consistency (how easily it spreads over the skin); for example if a product is thick (like a cream), a quarter-size amount in circumference is going to yield more product than one that has a liquid or fluid lotion texture.
You can get technical about it and use a method that involves milliliter/gram "serving sizes," but these measurements don't quite work out when comparing the amount of SPF product with a heavier cream texture versus a fluid lotion. (Generally, this seems to be an unreasonable task to ask of anyone just trying to get out the door in the morning.) The easiest solution? Stick to the nickel-to-quarter-size amount of sunscreen for the face, and the same for the neck.
If using the amount of sunscreen recommended above feels to heavy on your skin, the next best thing is to layer SPF products. For example, apply the amount of your daytime moisturizer with SPF that feels comfortable, but follow it with a foundation rated SPF 25 or greater and set that with a pressed powder that provides additional sun protection.
When to Apply Sunscreen
The vast majority of medical experts and skin researchers agree: Sunscreen is always, always, the final step in your skin-care routine. Any skin-care product applied over a sunscreen reduces the sunscreen's effectiveness to some degree. If you apply moisturizers or serums over your sunscreen, they reduce the amount of protection you get, and that is a serious problem. With the exception of a few naysayers, these guidelines are universally agreed on as the correct way to use sunscreen.
Note: Because most sunscreens have a moisturizing base, most people can skip applying "regular" moisturizer during the day—your sunscreen should provide enough moisture, so no need to layer moisturizer underneath it. Instead, consider applying an antioxidant-rich serum before your sunscreen to boost the skin's environmental defenses.
Note on the Note: 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 it is labeled "daytime moisturizer" or "sunscreen" and will provide you with the same UV protection benefits as long as it is rated SPF 25+ or greater and contains broad-spectrum UVA and UVB actives.
The primary difference between a daytime moisturizer with an SPF rating and a sunscreen is that the daytime moisturizer with sunscreen, in addition to the added sunscreen ingredients, typically also contains larger amounts of other beneficial ingredients (that is, greater levels of antioxidants and cell-communicating ingredients) than a "regular" sunscreen formula. Thus, a facial moisturizer with SPF tends to pack a greater anti-aging punch.
Do You Need to Wait to Go Outside After Applying Sunscreen?
Synthetic sunscreen actives (common examples include avobenzone, octinoxate, and oxybenzone) must be applied 20 minutes before exposing your skin to daylight because they need time to "get situated" and provide their protection (assuming you applied enough!).
Mineral sunscreen actives—titanium dioxide and zinc oxide—on the other hand, provide immediate sun protection, and it's not necessary to wait with these formulas. That's why we recommend using a mineral sunscreen for your hands when you're outdoors, and when you reapply after washing 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 and stabilized makes this a worry-free way to use your makeup and sunscreen formulas. In fact, many sun-care experts recommend layering like this to get maximum protection!
Applying Makeup Over Sunscreen
What about applying foundation (one that doesn't contain sunscreen) over the sunscreen you've just applied? This will dilute the sunscreen, but there are steps you can take to minimize the dilution:
- Wait 3–5 minutes for the sunscreen to set before applying foundation.
- Make sure you apply in smooth, downward motions.
- Do not use a rubbing or back-and-forth motion.
- Do not use excess pressure.
- Consider using a foundation sponge or brush rather than your fingers.
If you are not the sort to wait, opt for a foundation/tinted moisturizer with SPF 25+. Secondary to that, you may also wish to set your foundation with a pressed powder rated SPF 15 or greater.
We don't recommend using your makeup as your sole form of sun protection, because most of us won't use enough foundation (or tinted moisturizer, BB/CC Cream, etc.), that is, won't apply it liberally (or evenly) enough to get the SPF protection listed on the bottle.
Can you mix your tinted moisturizer or foundation with your sunscreen to counteract the white cast of a mineral formula? Yes—as long as your moisturizer or foundation is rated SPF 25+, you can mix either one with your sunscreen. If your tinted moisturizer or foundation is not rated SPF 25+, it's OK to mix a few drops of it into your sunscreen, but no more than that or you risk diluting your sun protection.
Do not rely on powders that contain sunscreen for your sole SPF protection, as most people do not apply pressed-powder foundations liberally enough to get the amount of protection stated on the label (and with good reason, as doing so requires a lot of powder)!
Although pressed (or loose) powders are an iffy way to get sun protection for the face, they are a great way to touch up your makeup during the day and reapply more sunscreen at the same time.
What Do PA++ and PPD Mean?
The letters PA followed by plus signs (PA++, PA+++) on a sunscreen product label are a rating system developed and used in Japan. Although this system is interesting, it has its drawbacks. The PA system concerns only UVA protection; PA++ indicates moderate UVA protection, PA+++ indicates high UVA protection. Some regulatory experts argue that this type of test isn't reliable because it looks only at UVA radiation, while natural sunlight is a mix of UVA and UVB, each of which damages skin, although in different ways.
The other issue is that PA++ ratings are determined based on what's known as "persistent pigment darkening" or PPD. That sounds reasonable—if your skin gets darker, then the UVA rays, which cause tanning, are getting through. In the testing, however, even on people who have the same skin tone initially, the color their skin turns after UVA exposure is routinely inconsistent, some darker, some lighter.
So, PA testing differs from the UV critical wavelength testing used to test sunscreens in the United States and European Union (EU). The U.S. and EU method is considered more reliable because the subjects are exposed to the UV light (both UVA and UVB) they will encounter in real-world settings and the sunscreen's UV protection ability is measured against this type of exposure.
Regardless of the issues with the PA rating system, a well-formulated sunscreen will provide broad-spectrum protection and, as with any sunscreen, should be applied liberally and reapplied as needed to maintain protection. But, as explained above, in most scenarios the "reapply every two hours no matter what" guideline is not only impractical, but also truly unnecessary.
The Bottom Line
On a normal day, which generally means to and from work and a short walk at lunch, an effective amount of sunscreen applied in the morning is still going strong when you're done with work and on your way home. While understanding sunscreen isn't necessarily easy, if you remember to apply broad-spectrum SPF 25+ daily, reapply every 40 to 80 minutes when sweating or swimming, or after every few consecutive hours of direct daylight exposure, you will keep your skin young and reduce your risk of brown spots, sagging, and, most important, skin cancer!
Learn more about what the sun is doing to your skin and how you can prevent it. See our sunscreen infographic.
The Best Skin of Your Life Starts Here: The same type of in-depth scientific research used to create this article is also used to formulate Paula’s Choice Skincare products. You’ll find products for all skin types and a range of concerns, from acne and sensitive skin to wrinkles, pores, and sun damage. With Paula’s Choice Skincare, you can get (and keep) the best skin of your life! See Paula's Choice Sun Protection Products.