Celebrating National Sunscreen Day: How Your SPF Really Works and Why Better Options Are Coming

Thick and creamy, gloopy or spray-on, sunscreen can be confounding. Some formulations are heavy and chalky, while others are clear and lightweight. Some come as lotions; others are sprays, sticks, or gels. Then there are the labels: “broad spectrum,” “water-resistant,” and the ever-present SPF (Sun Protection Factor). What do these numbers really mean, and how high is high enough?

As we recognize National Sunscreen Day, let’s explore how sunscreen works, how to use it properly, and how U.S. formulations are about to improve—sooner rather than later.

How Sunscreen Protects You from the Sun

Ultraviolet (UV) radiation from the sun damages the DNA in our skin cells, which can cause skin cancer, premature aging, and wrinkles. Sunscreen typically protects our skin from those harmful rays in two ways: by blocking UV light, absorbing it, or both.

There are basically two types of sunscreens available today:

• Mineral (or Physical) Sunscreens: Made with active ingredients like zinc oxide and titanium dioxide, these act as nanoparticle-sized “mirrors” that reflect UV radiation and visible light (though research shows they also absorb some UV light). They tend to leave a pasty, white finish on the skin.
• Chemical Sunscreens: These utilize molecules that absorb different wavelengths within the UV spectrum. They convert the absorbed UV light into heat, which is then released from the skin. These formulations are typically transparent and don’t leave a white sheen.

The Problem with SPF: UVB vs. UVA

SPF measures a sunscreen’s ability to protect you from burning, but there is a catch: it specifically measures protection from ultraviolet B (UVB) light, which has a wavelength between 280 and 315 nanometers. While UVB exposure aids in the synthesis of vitamin D, it is also the primary cause of sunburn, redness, and inflammation.

For decades, sunscreen manufacturers prioritized products that protected against UVB. However, scientists now know that ultraviolet A (UVA) light—with a wavelength between 315 and 400 nanometers—also significantly raises the risk of skin cancer. This risk isn’t captured by the SPF metric. If your sunscreen protects against UVB but not UVA, it may keep you from getting a sunburn, but it still leaves you vulnerable to long-term sun damage.

Sunscreens labeled as “broad spectrum” are designed to protect against both UVB and UVA light. However, the U.S. currently lacks a standardized, SPF-like measurement for UVA, meaning you cannot definitively know how much UVA protection a “broad spectrum” sunscreen provides.

In other parts of the world, including Asia and Europe, a metric called UVA-PF (UVA Protection Factor) is used. It measures UVA protection using a rating scale from PA+ to PA++++. Currently, the U.S. Food and Drug Administration (FDA)—which oversees sunscreen—does not require or regulate this metric.

How U.S. Sunscreen Formulations Are Changing

Traditional sunscreens are designed to block ultraviolet radiation at the skin’s surface. However, UV exposure initiates deeper biological effects—including oxidative stress, DNA disruption, and microbiome imbalance—that continue even in the absence of a visible burn.

True photoprotection must extend beyond surface filtration to address these underlying injuries. At Columbia Skincare, we have developed a sunscreen platform that stabilizes the skin across molecular, cellular, and microbial layers. By integrating these systems, we move from passive protection of the skin to active biological support. This enhances the skin’s ability to defend, repair, and adapt itself under UV stress.

How to Choose the Best Sunscreen

The answer to this is simpler than you might think: the best sunscreen available is the one that you will actually wear! If a sunscreen doesn’t have a look and feel that you like, you won’t use it consistently.

Sunscreens available in Europe and Asia often offer a wider variety of active ingredients. This is because the U.S. FDA regulates sunscreens strictly as drugs, rather than as cosmetics. However, progress is being made. The FDA recently approved a new ingredient called bemotrizinol—commonly found in Asian and European formulations—for use in the U.S. This marks the first new sunscreen ingredient allowed in the country since 1999.

Final Thoughts

Certainly, sunscreen isn’t your only line of defense. Avoiding peak sunlight hours, wearing a hat, covering up with UPF clothing, and sticking to the shade are safe, effective ways to reduce your risk of harmful sun exposure. We at Columbia Skincare cannot overemphasize the value of these physical means of sun protection.

We wish all of you a healthy, sun-safe summer!