Midsummer UV Final Defense — Preparing for Four Layers: UVA, UVB, Visible Light & Near-Infrared

KAIAN R&D Team | Published: July 28, 2026

The 2026 rainy season ended earlier than usual, and since late July, mainland Japan has seen 35°C days almost daily. The UV index has stayed at "very high," among the highest levels in two decades. What many people overlook this summer is the assumption that "UV protection = not turning red."

In fact, recent research shows that the deepest contributors to skin aging are not UVB, but a three-layer structure of UVA, visible light (HEV), and near-infrared (IR-A).

1. The Four-Layer Threat — Skin Damage by Wavelength

UV light and its adjacent wavelengths differ in skin penetration depth and damage by band.

Of particular note are HEV (high-energy visible light) and blue light. Emitted daily from smartphones and LED lighting, they worsen pigmentation-type spots (especially melasma) even indoors. And near-infrared (IR-A) penetrates deepest, reducing fibroblast mitochondrial function and chronically eroding collagen and elastin production — the "hidden culprit of photoaging."

2. Why "SPF50+ / PA++++" Alone Is Not Enough

SPF is a protection index against UVB, and PA reflects protection up to UVA-II. But most commercial sunscreens do not account for HEV and IR-A protection at the design stage. Even applying SPF50+ / PA++++ daily, visible light and near-infrared pass straight through — the standard spec of the cosmetics aisle.

From the Skin Longevity perspective, protection should be designed in "layers," not as a single "point." We believe a layered approach is needed — physical × chemical × antioxidant, plus 24-hour continuous internal antioxidation that assumes you will miss spots.

3. The KAIAN View — Skin Longevity Triple Design

The UV defense KAIAN recommends has the following triple structure.

1. Physical block layer (Zinc Oxide / Titanium Dioxide): stable defense that scatters and reflects at the surface. Low irritation even for sensitive skin, and partially blocks visible light.
2. Chemical block layer (Tinosorb S / Uvinul A Plus): broadband absorption up to UVA-I. Next-generation filters with high photostability that resist degradation.
3. Internal antioxidant layer (Vitamin C / Ferulic Acid / Resveratrol / Lycopene / Lutein): neutralizes ROS after penetration, suppressing DNA damage and MMP activation.

For visible light (HEV), a tinted formula containing Iron Oxides (a lightly tinted type) is effective.

4. Practical Protocol — Three-Layer Defense, 24-Hour Design

Morning (before going out): ① antioxidant serum → ② moisturize → ③ physical + chemical sunscreen → ④ tinted (iron oxide) foundation for visible-light protection.

Daytime (every 2-3 hours): reapply with powder, stick, or spray types that go over makeup.

Night: repair daytime DNA damage with Retinol, suppress MMP with Niacinamide, and continue internal antioxidation with oral lycopene and lutein.

The guideline application amount is about 0.8 g for the whole face (two fingertip units). Most people apply less than half this in practice, dropping effective SPF to a half or a third of the label value.

5. How to Choose Sunscreen — KAIAN's "Three Conditions"

KAIAN does not recommend specific third-party products. Instead, we share "conditions" you can verify on the ingredient label at the store. Meet these, and regardless of brand, you can build sufficient protection from the Skin Longevity perspective.

6. [Trend Check] Do "Oral Sunscreens" Really Work?

TREND CHECK / KAIAN grades buzzwords with science

"Oral sunscreens" are gaining presence on social media and in drugstores. In short, they are a complement, not a replacement, for topical sunscreen. Oral antioxidants suppress body-wide ROS that topicals cannot reach, backing up missed spots from the inside — but their power to block UV at the surface is far below topical agents.

Grading the strength of evidence by ingredient reveals clear differences.

• PL Extract (Fernblock) [A]: multiple human studies show MED elevation and CPD suppression. The best-evidenced oral photoprotection, used dermatologically.
• Nutroxsun [A−]: clinical data showing significant reduction of UV erythema after 12 weeks.
• Astaxanthin / Lycopene [B]: antioxidant action is solid, but UV-protection trials are limited.
• Single vitamins [C]: weak photoprotection evidence when taken alone.

Oral sunscreen is not "magic that lets you skip applying." With topical application as the foundation, treat it as the first stage of a "two-stage" approach that boosts protection from within — the correct use from a Skin Longevity perspective.