Sunscreens remain a foundational component of dermatologic photoprotection, yet traditional formulations fall short in defending against the full spectrum of solar radiation, particularly long-wavelength ultraviolet A (UVA1: 340–400 nm) and visible light (VL: 400–700 nm). A review published in Photodermatology, Photoimmunology, and Photomedicine highlights recent scientific developments aimed at improving sunscreen efficacy through novel filters and formulation innovations.
Historically, sunscreens have been effective primarily against ultraviolet B (UVB: 290–320 nm) and short-wavelength UVA (UVA2: 320–340 nm), which are largely responsible for erythema and direct DNA damage. However, long-wavelength UVA1 penetrates more deeply into the skin, generating reactive oxygen species that accelerate photoaging and contribute to carcinogenesis. Additionally, visible light—especially in the blue-violet range—has been implicated in hyperpigmentation, particularly in darker skin types. Despite this, current sunscreens rarely provide adequate protection in these ranges.
The U.S. FDA defines "broad-spectrum" sunscreens as those with a critical wavelength of at least 370 nm, covering UVA2 but not the full UVA1 or VL spectrum. The SPF rating further emphasizes UVB protection, creating a regulatory and perceptual gap in comprehensive skin safety.
A key challenge in enhancing sunscreen protection in the United States lies in the stringent regulatory framework. UV filters are treated as over-the-counter drugs, requiring robust safety and efficacy data for approval. Unlike the European Union, which has approved 29 UV filters (regulated as cosmetics), the U.S. FDA has only authorized 16 filters—with no additions to its monograph in over 25 years. Currently, only zinc oxide and titanium dioxide are categorized as GRASE (Generally Recognized as Safe and Effective), highlighting the regulatory inertia limiting innovation in the U.S. sunscreen market.
Sunscreen filters are generally categorized as inorganic (mineral) or organic (chemical). Inorganic filters like zinc oxide and titanium dioxide reflect and scatter UV and some visible light. However, their cosmetic acceptability is limited due to the chalky white residue they leave on the skin—especially noticeable in darker skin tones. The adoption of nanoparticle forms (<100 nm) has improved aesthetics but reduced visible light protection. Organic filters, in contrast, absorb UV radiation via electron excitation. These filters vary in photostability, necessitating the use of stabilizers or combinations for broader coverage. While traditional organic filters like avobenzone, oxybenzone, and octinoxate provide solid UVB and UVA coverage, they are less effective against long UVA and VL.
Several novel filters have been developed internationally and offer broader protection. Bemotrizinol (BEMT) has high photostability and a broad absorption range (305 and 360 nm). Though used globally, it is still under FDA review. Mexoryl 400 (MCE) absorbs strongly at 385 nm and offers significant protection in the UVA1 range. Clinical trials demonstrate its superior efficacy in preventing UVA-induced hyperpigmentation. TriAsorB (PBDT) stands out for extending coverage into the high-energy visible light range (up to 450 nm). It is photostable and has a light yellow hue, making it a promising candidate for enhanced VL protection. Additionally, iron oxides are increasingly used in tinted sunscreens to provide VL protection, especially valuable for people with melanin-rich skin who are more prone to pigmentary disorders.
Despite regulatory and technical challenges, the field of sunscreen science is rapidly evolving. New filters like BEMT, MCE, and TriAsorB are addressing critical gaps in UVA1 and VL coverage, while innovations in formulation—such as nanoparticle technology and pigment additives—enhance both efficacy and user experience. As dermatologic needs and photoprotection awareness grow, regulatory flexibility and continued research will be essential in making these advanced filters more accessible, especially in the U.S. market.
Sources: Photodermatology, Photoimmunology, and Photomedicine