Main content

How Does Sunscreen Work to Protect Your Skin

Model with graphic overlay on her face showing how does sunscreen work to protect skin

To better understand the importance of SPF and sunscreen, we asked Kayte Epperly, Scientific Communication Liaison at L’Oreal Research & Innovation US Skin Care Development, how does sunscreen work and how to use sunscreen effectively in your daily routine.

How Does Sunscreen Work?

Sunscreen works by utilizing physical and chemical mechanisms to protect the skin from the harmful effects of the sun's ultraviolet (UV) radiation. Sunscreen effectiveness can vary based on factors such as the SPF (Sun Protection Factor) level, application amount, and frequency of reapplication.

The Sun’s UV Rays: UVA & UVB

Many sunscreens provide broad-spectrum protection from the sun’s damaging UV rays, which means they offer defense against both UVB and UVA rays. UVA rays are known as “aging rays” and overexposure can cause skin damage, leading to visible signs of premature aging, such as wrinkles, sagging, and dark spots. While UVB rays, also known as “burning rays,” are the primary cause of sunburn.

Mineral-Based Sun Protection

Some sunscreens contain mineral-based ingredients like titanium dioxide or zinc oxide. These sunscreens are called mineral sunscreens, also known as physical sunscreens, as these minerals act as a physical barrier between your skin and the sun. Mineral sunscreen formulas will sit on top of the skin and reflect or scatter UV rays away from the skin's surface. This helps to prevent the rays from penetrating the skin and causing damage.

Organic-Based Sun Protection

Other sunscreens contain organic compounds that work by absorbing UV radiation. These are called chemical sunscreens. And their compounds, such as avobenzone or octisalate, have specific chemical structures that allow them to absorb UV rays and convert them into less harmful forms of energy, such as heat. This absorption process helps to prevent UV rays from reaching deeper layers of the skin and causing damage.

What SPF Should I Use?

Sun Protection Factor, or SPF, is a measure of a sunscreen’s ability to block UVB rays from damaging the skin. When it comes to SPF level, a higher SPF doesn’t mean it protects skin for a longer amount of time; rather, that means it can block a slightly higher percentage of rays relative to unprotected skin. The American Academy of Dermatology recommends a minimum SPF 30 or higher for daily use, which filters out approximately 97% of UVB rays, while SPF 50 filters out approximately 98% of UVB rays. Look for the label “broad spectrum” when comparing sunscreens to make sure you’re covered from both UVA and UVB rays.

When Is Sun Damage Most Likely?

The higher the sun, the stronger the rays. The sun's rays are strongest between 10 a.m. and 4 p.m. during daylight saving time (or between 11 a.m. and 5 p.m. during standard time). During these hours, the UV radiation is more intense, increasing the risk of sun damage. If you’re out at midday, you may need a higher SPF to help protect you, along with taking other sun protection measures, such as staying in the shade and wearing a hat or sun-protective clothing.

Do I Need Sunscreen If I Have a Darker Complexion?

Everyone should always wear sunscreen if they will be exposed to the sun, including people of color. While melanin, the pigment in skin, does offer some natural protection from sun damage and skin cancer risk — leading to a false sense of immunity — it’s nowhere near the minimum SPF 30 recommended by the American Academy of Dermatology. Every skin tone, including brown and black skin, can develop skin cancer, and therefore, requires daily sun protection.

How Much Facial Sunscreen Should I Apply?

The general recommendation is to apply about a nickel-sized amount of sunscreen for the entire face, or approximately 2 milligrams of sunscreen per square centimeter of skin, according to The Skin Cancer Foundation. However, everyone's face size varies, so you may need to adjust the amount accordingly. If you want to ensure thorough coverage, squeeze out 3 finger-lengths of sunscreen. When applying sunscreen, make sure to cover not only your cheeks and forehead, but also your nose, ears, neck, and any other exposed areas on your face. Pay attention to sensitive areas as well, like the under-eye area, the bridge of the nose, and the lips, which are also prone to sunburn, so be sure to apply sunscreen to these areas too.

While applying, blend and massage the sunscreen formula into your skin, ensuring even coverage and absorption. Pay attention to any areas where the sunscreen may have settled into fine lines or creases and smooth out. Lastly, remember to reapply sunscreen every 2 hours or more frequently if you are sweating or wiping your face. If you like wearing makeup, consider using a face powder or spray sunscreen for easier reapplication without disturbing your makeup.

How Long Does Sunscreen Last?

The protection of sunscreen lasts about 2 hours, which is why dermatologists and the FDA recommend reapplying after that. That timeline gets shorter if you introduce anything that can wash it away, like sweat or jumping in the pool. So, if you’ve just gone for a run or swim, reapply immediately after drying off and repeat as needed. While sunscreen can’t technically be waterproof, some sunscreens may be labelled “water-resistant”, which will provide such protection for a short period of time, typically 40 or 80 minutes.

What’s the Difference Between Mineral Sunscreen & Chemical Sunscreen?

As we touched on before, there are 2 types of sunscreen: mineral or physical sunscreen and chemical sunscreen. Chemical sunscreens use active ingredients such as oxybenzone and avobenzone that sink into the skin and absorb the UV energy released by the sun – like a sponge for sunlight. Mineral sunscreens, also known as physical sunscreens, contain actives such as zinc oxide and titanium dioxide that sit on the skin’s surface, creating a physical barrier and reflecting UV rays from the skin.

Which Is Better: Mineral vs Chemical Sunscreen

The best sunscreen for you really depends on your preferences, skin type, and which sunscreen formula you’re willing to apply every day. In other words, the best sunscreen for you is the one you like using, given consistent daily application is critical for minimizing sun-induced skin damage.

Choosing between a mineral or chemical sunscreen is a matter of preference and skin type, as both can be highly effective if used as directed. You may also like to apply a combination of both. Chemical sunscreens are absorbed by skin, so you often get more even coverage with it. Mineral or physical sunscreens are better for those with sensitive or post-procedure skin, but, because they form a physical barrier on the skin’s surface, need to be applied more thoroughly and evenly. Chemical sunscreens are also less likely than mineral sunscreens to leave a chalky residue or white cast. Chemical sunscreen formulas blend into the skin quickly, whereas a mineral sunscreen may take longer to fully rub in and may leave a sheen on skin.

Does Sunscreen Expire?

Yes, sunscreen does expire. Most sunscreens have an expiration date printed on the product packaging. If you can’t find an expiration date, it should be okay to keep for about 3 years from the date you purchased it, according to the U.S. Food and Drug Administration.

If you can’t remember when you bought your sunscreen, or if it’s indeed expired, it’s generally recommended to discard and replace it with fresh product. Expired sunscreen may not provide the level of protection stated on the label and using it could increase the risk of sunburn and sun damage.

To ensure the effectiveness of your sunscreen, it's best to check the expiration date before use and store it in a cool, dry place away from direct sunlight. Additionally, if you notice any changes in the texture, smell, or consistency of the sunscreen, it's advisable to replace it, even if it hasn't reached its expiration date.

Can You Still Tan with Sunscreen?

You may be relieved to learn that you don’t need to forgo your long-anticipated summer glow because you wear sunscreen. Because, yes, it’s still possible for you to get a tan while wearing sunscreen – remember, SPF 30 filters out approximately 97% of damaging UVB rays, SPF 50 filters out approximately 98%, and no sunscreen or SPF level can block 100% of UVB rays. It’s worth mentioning that a tan is a sign of skin damage, and excessive exposure to UV radiation can increase the risk of skin cancer and premature skin aging. It's always advisable to prioritize sun protection and use sunscreen as part of your sun safety routine.

If your goal is to prevent tanning altogether, you’ll want to take additional sun protection measures. Stay in the shade, wear protective clothing, use broad-brimmed hats and sunglasses, and most importantly, reapply sunscreen throughout the day, especially after swimming or sweating, as it can wear off.

Do You Apply Sunscreen Before or After Moisturizer?

Sunscreen is typically the last step in your daytime skincare routine and is applied after moisturizer. Allow the sunscreen to absorb into your skin before applying makeup, if desired. If you like to use powder makeup with an SPF of 30 or higher, you can also apply this as the last step in your makeup routine.

Sunscreen in Makeup

Though your foundation or makeup primer may have a relatively high SPF number, this doesn’t guarantee you’ll receive adequate protection – especially in the summertime. Many makeup products don’t offer broad-spectrum protection (protection against both UVA and UVB rays), so you might not be protected against those burning UVB rays. Having sunscreen built into your makeup can be convenient, but when we apply foundation or face products, we typically only apply as much product as needed to cover our skin or create an even toned complexion, and this is not enough product to protect you.

Lancôme Sun Protection

Lancôme’s UV Expert Sunscreen with SPF 50 is an SPF with makeup primer benefits, as well as a daily moisturizer, all-in-one, and is recommended for daily use by the Skin Cancer Foundation. Consisting of a water-like gel formula, which feels lightweight on the skin, UV Expert is considered a chemical sunscreen and is an excellent formula to wear on bare skin or underneath makeup as a moisturizing primer. It’s easy to blend and leaves skin feeling hydrated without any greasiness or white residue. Thanks to its mineral oil-free and non-comedogenic formula, it’s suitable for all skin types, including sensitive skin.

UV Expert Defense SPF 50+ Primer & Moisturizer

UV Expert Defense SPF 50+ Primer & Moisturizer

Protecting & Hydrating

Old price New price $48.00

Lancôme’s moisturizing creams with SPF, like Rénergie Lift Multi-Action Day Cream with SPF 15 and Rénergie H.P.N. 300-Peptide Cream SPF 25, combine anti-aging benefits with additional daily sun protection. These daily anti-aging moisturizers help visibly firm skin to address the visible signs of aging and leave skin feeling hydrated and fresh. These two lightweight day creams smooth over skin without the formulas gathering or peeling, making these another great option to wear underneath makeup – just make sure to pair them with a sunscreen that offers SPF level 30 or higher for effective sun protection.


Orientation message
For the best experience, please turn your device