The Dermatology Digest • Innovations in Pre-, Peri-, and Post- Procedure Skincare December 2025 • MEETING HIGHLIGHTS

Evaluating UVA Protection in Mineral Sunscreens: How Do US Products Stand Up?

Sun Protection Factor (SPF) has become a go-to guide for sun safety, but it primarily reflects protection against UVB rays, which cause sunburn.

UVA rays, which penetrate more deeply and contribute to pigmentation, premature aging, and skin cancer risk, are less clearly addressed by SPF alone. This study set out to answer the question: How well do US mineral sunscreens protect against UVA-induced pigmentation, and how much does that protection vary by product type?

For the study, researchers applied different mineral sunscreen products to the skin of healthy men and women ages 18–70 with Fitzpatrick skin types II–IV; then used a controlled UVA light source to simulate sun exposure and trigger pigmentation. They then measured the degrees of pigmentation using colorimetric analysis.

In total, they tested 18 broad-spectrum mineral sunscreens with SPF ratings between 30 and 70, getting at least 10 valid test results for each sunscreen.

In addition, the researchers tested eight of these sunscreens in a lab to see how product type influences UVA protection. The formulations they tested included pure mineral sunscreens, mineral-chemical blends, tinted mineral sunscreens, and tinted mineral-chemical blends.

UVA protection and photostability varied widely across sunscreen types, even though all were labeled “broad spectrum,” the study showed. Broad-spectrum labeling did not guarantee balanced protection. UVA Protection Factor (UVAPF)-to-SPF ratios ranged from 0.11 to 0.61. (For reference, the EU requires a ratio of 0.33 to be considered broad spectrum). What’s more, tint affected performance differently: It improved UVA protection in pure mineral formulas but reduced it in mineral- chemical blends.

SPF was not a reliable predictor of UVA protection. SPF 30–40 products had UVAPFs of 4.5–18.3; SPF 41–50 had UVAPFs of 5.5–8.8; and the SPF 70 product delivered the highest UVAPF of 25.8. Mineral-chemical blends generally performed weakest, while pure mineral and tinted mineral sunscreens delivered stronger UVA protection and better photostability.

Formula aesthetics matter, the researchers noted. Spreadability and feel influence real-world use, underscoring the need to balance effcacy and cosmetic appeal in new sunscreen formulations.

The study authors recommend selecting sunscreens from reputable brands with demonstrated UVA protection and encouraging proper, adequate application.

Tretinoin and retinol are powerhouse ingredients used to treat acne, psoriasis, and symptoms of photoaging—but they can be irritating, causing redness, scaling, and dryness. Which is why some clinicians recommend layering them with moisturizers. But does that make retinoids less effective? This study sought to find out.

Researchers tested 0.1% retinol cream and 0.025% tretinoin cream with lightweight water gel and water cream moisturizers on human skin samples (explants) from abdominoplasty. Regimens included (1) retinoid alone, (2) an “open sandwich” method (moisturizer before or after retinoid) and (3) a “full sandwich” method (moisturizer before and after retinoid).

After 48 hours, they assessed changes in retinoid bioactivity by measuring HBEGF and HAS3 gene expression, which show how the skin responds to retinoids.

Skin samples treated with the “full sandwich” regimen demonstrated reduced retinoid bioactivity as shown by HBEGF gene expression, indicating lower penetration. Skin samples treated with the “open sandwich” regimen (moisturizer before or after retinoid) maintained comparable bioactivity to the retinoid treatment alone, as shown by HBEGF gene expression as well as by HAS3 gene expression.

The “full sandwich” method lowers retinoid penetration and can be a gentle approach to introducing retinoids or for patients experiencing irritation.

The “open sandwich” regimen preserves bioactivity while offering potential benefits in skin tolerability and hydration and should continue to be recommended for patients who wish to use retinoids with minimal irritation.

Mineral Sunscreens Labeled 'Broad Spectrum' Can Differ in How Well They Block UVA Rays

Products with more zinc oxide usually show better UVA filtering than other mineral blockers in lab tests, but it’s not clear how much that translates to preventing UVA damage in real life.

This study set out to bridge that gap by comparing the lab results for mineral sunscreens that contain zinc with their real-world performance. It also looked at whether higher zinc oxide levels heighten UVA protection.

The single-center, randomized, self-controlled clinical trial measured UVAPF using the ISO 24442:2011 standard. The method is based on the persistent pigmentation darkening (PPD) response of the skin to UVA exposure. Researchers tested eight broad-spectrum mineral sunscreens containing 0%–21.6% zinc oxide on healthy men and women, ages 18–70, with Fitzpatrick skin types II–IV.

They took cross-polarized photos of the skin before and after UVA exposure and then measured the resulting skin darkening using a color scale called individual topology angle (ITA), which quantifies even subtle changes in skin tone. For each person, they also determined the smallest UVA dose that caused a clear, lasting dark spot—known as the minimal persistent pigmentation darkening dose (MPPDD)—so they could compare how well different sunscreens prevented that reaction.

The test produced consistent results across all skin tones studied, showing it was reliable for evaluating UVA protection and reinforcing the idea that everyone—across the spectrum of skin tones—needs UVA protection. Zinc oxide improved UVA protection. Sunscreen formulations with higher zinc oxide levels required up to 18 times more UVA exposure to cause skin darkening compared to those without zinc, providing roughly twice the protection of an SPF 50 sunscreen without zinc oxide.

The authors added that real-world sunscreen use depends not only on photoprotection performance but also on texture and cosmetic appeal, and they called for more research to optimize both. Dd.