Regulatory landscape you can’t ignore (US & EU)
- US (FDA): dosage-form scrutiny just got real. On Aug 6, 2025 the FDA issued warning letters to brands marketing mousse/whip/foam sunscreens, stating these formats are not among the GRASE OTC dosage forms and therefore require an approved application or order. If you sell into the U.S., stick to monograph dosage forms (oil, lotion, cream, gel, butter, paste, ointment, stick, spray, powder) or be prepared for an NDA/CR. Read the letters (they specify the legal basis and 15-day response clock).
- EU (filters & restrictions): The EU added Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate (aka “Mexoryl 400 / MCE / S87”) at up to 3% (with nitrosamine and inhalation caveats). This gives strong long-UVA coverage. Also expect enforcement of Homosalate reductions in face-only products per 2022/2195 (applicable from July 1, 2025).
- Testing standards (global): ISO published two new SPF methods:
• ISO 23675 (2024/2025): first 100% in-vitro SPF (“Double Plate Method”) for emulsions and certain one-phase products.
• ISO 23698 (2024/2025): Hybrid Diffuse Reflectance Spectroscopy (HDRS)—combines in-vitro + optical on-skin readout to estimate SPF, UVA-PF, critical wavelength without inducing erythema.
Both correlate to legacy ISO 24444/24443 and are being adopted in labs; U.S. OTC adoption will require FDA acceptance. - Water resistance labelling: Still anchored in ISO 16217 (immersion) + ISO 18861 (WR%) with ISO 24444 for SPF. Align your study designs and claims language accordingly.
Filter tech & spectral strategy (what’s working now)
- Long-UVA/near-visible closer: EU-only filters like MCE (Mexoryl 400) and Phenylene Bis-Diphenyltriazine (TriAsorB / BPT) extend protection deeper into UVA1/HEV (~450 nm) and enable high UVA-PF while keeping elegant textures. If you’re formulating for EU/APAC, they are your easiest path to “spectral homeostasis.”
- US-only realities: You’ll still rely on avobenzone (photolabile) + octocrylene/oxybenzone (where allowed) and/or mineral ZnO to lift UVA. Photostability management remains a core task (see below). For brand portfolios spanning regions, plan region-specific filter stacks and keep the rheology & sensorials consistent across chassis. (Summary based on up-to-date overviews of US/EU filter rosters.) PMC
- Tinted/iron-oxide hybrids: Iron oxides meaningfully reduce HEV-induced hyperpigmentation (e.g., melasma relapse) when dosed/tinted correctly—now mainstream in derm-focused lines. Pair with high UVA-PF for real-world pigmentation control.
Testing & claim-building (what to change in your dossiers)
- Pilot with ISO 23675/23698: Use the new methods early in development to pre-screen SPF/UVA-PF and iterate faster, then confirm with ISO 24444/24443 (and FDA 2011 method for US claims). This shortens loops and reduces volunteer exposure. Note: FDA has not yet recognized 23675/23698 for OTC sunscreen drugs.
- Water resistance proof: If you say “Water Resistant,” run ISO 16217 + 18861 (EU/ROW) and/or FDA 40/80 min (US). Ensure dossiers show retention % and immersion schedule; harmonize language across regions.
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Formulation tips that work in 2025
A) Photostability & filter efficacy
- If using avobenzone (US):
• Add octocrylene or encapsulation/UV-stabilizers to curb photodegradation; consider antioxidant couples (TOC/TPP, tocopherol + ferulic) to buffer ROS.
• Keep avobenzone ≥2–3% when you need robust UVA-PF and aim for critical wavelength ≥370 nm. Validate by UVA-PF (ISO 24443/23698). (General guidance; see stability literature on avobenzone delivery.) - Mineral systems:
• Use alumina/silica/silicone-coated ZnO/TiO₂ dispersions; target D50 ~120–200 nm with narrow PSD for opacity vs. transparency balance.
• Rheology modifiers (e.g., silica aerogels, elastomer gels) plus high-SPF film formers help maintain SPF-in-use and water resistance. - EU/APAC long-UVA builds:
• Combine MCE (≤3%) + BPT/TriAsorB (≤5%) + a UVB workhorse (DBT/DEBT, OMC, etc.) to hit high SPF with strong UVA-PF ≥ 1/3 SPF (EU rule of thumb). Check nitrosamine controls for MCE (secondary amine; <50 ppb nitrosamine; avoid nitrosating agents).
B) Film formers & water resistance
- For 40/80-min claims (US) or WR% (ISO), layer hydrophobic film formers (e.g., acrylates/octylacrylamide copolymer, certain silicones, polyurethane-based options), plus waxes as required in sticks. Confirm sebum/water rub-off and immersion performance; document wash-off mass loss if your QA requires it. Validate with ISO 16217 + 18861 or FDA 2011.
C) Sensory engineering (no white cast)
- In mineral SPFs, reduce whitening via: neutral-density tinting (iron oxide blends matched to Lab* targets), high-RI emollients, and optically clear elastomers. Bench screen on Fitz I–VI panels; measure ΔE vs. bare skin.
D) “Serum” & light textures (and what to avoid in US)
- Serum/gel-cream chassis are in demand, but if you sell in the U.S., avoid mousse/whip/foam unless you’re pursuing an FDA application. Align package cues to avoid food-like presentation (another FDA concern).
E) Pigment & HEV strategies
- For melasma/PIH audiences, incorporate iron oxides (black/red/yellow) in tinted bases and communicate UVA + visible coverage with UVA-PF + critical wavelength plus instrumented HEV transmission where available.
Product formats & claims consumers want (that you can safely make)
- Daily wear “SPF + skincare”: Niacinamide, panthenol, ectoin, and photostable antioxidant systems that don’t quench filters are hot. Back anti-pollution/IR claims with antioxidant outcome assays (not just INCI lists).
- Tinted mineral “derm shades” for darker skin tones—expand shade range, keep iron-oxide levels high enough to matter, and test stain-resistance on clothing.
- Sticks for reapplication—high wax/film former; test in-use SPF after multiple passes and under sweat conditions.
- Sprays (US): follow particle size/flammability guidance and label warnings; stay away from benzene-risk propellants from compromised supply chains (internal QA spec + third-party impurity screens).
Practical development workflow (2025-ready)
- Design for region: EU/APAC: leverage MCE + BPT; US: maximize ZnO + avobenzone systems with robust stabilization.
- Screen early: Use ISO 23675 (in-vitro) or ISO 23698 (HDRS) to cut cycles; select finalists for ISO 24444/24443 (and FDA 2011 if US).
- Lock water resistance: Build films, then verify via ISO 16217/18861 (and US 40/80 min).
- Pigment strategy: For anti-hyperpigmentation lines, add iron oxides and instrument HEV/UVA1 transmission.
- Reg check before scale-up: Confirm dosage form legality in the U.S. (no foams/mousses/whips without an FDA order/NDA).
Key sources (starter pack)
- FDA warning letters on mousse/whip/foam sunscreens (Aug 6, 2025): primary evidence of US dosage-form enforcement.
- ISO 23675 (2024/2025) & ISO 23698 (2024/2025): new SPF methods (in-vitro DPM and HDRS hybrid), with industry commentary on adoption.
- ISO water-resistance standards: ISO 16217 (immersion) & ISO 18861 (retention %).
- EU filter updates & limits: SCCS S87/MCE safe at ≤3% with nitrosamine caution; Homosalate restrictions applicable from July 1, 2025.
- Long-UVA & HEV protection (BPT/TriAsorB, iron oxides): dermatology and industry write-ups; practical endpoints.
Final takeaways
- Build region-specific filter stacks; don’t ship mousse/foam formats in the U.S. without a regulatory pathway.
- Use ISO 23675/23698 to accelerate R&D, then confirm with legacy in-vivo methods for market claims.
- For pigmentation-centric lines, iron oxides + high UVA-PF are your differentiator.
- For water sports lines, invest in film formers + ISO WR studies early—don’t retrofit.
Resources:
U.S. Food and Drug Administration
European Comission Public Health
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