Ethylhexyl Triazone in Sunscreens: The Need of Reassessment Based on Modern Evidence

A legacy approval in a modern context

Ethylhexyl Triazone, commonly listed as EHT or Uvinul T 150, has been used in some chemical sunscreens for its ability to strongly absorb UVB radiation and remain photostable on the skin. Its regulatory acceptance in Australia and parts of Europe is rooted in safety evaluations conducted in the late 1990s. Those evaluations were completed under regulatory frameworks that did not require human pharmacokinetic studies, long-term dermal carcinogenicity testing, endocrine screening, or comprehensive impurity qualification. Nearly three decades later, that original evidentiary position has not been meaningfully updated in the public domain.

A safety profile built on absence rather than demonstration

Publicly available data suggest that Ethylhexyl Triazone has low acute toxicity and does not trigger obvious red flags in short-term screening tests, a conclusion reflected in the TGA’s 2025 review, which classified the ingredient as low risk under current use conditions. However, the absence of short-term toxicity is not equivalent to demonstrated long-term safety. For a substance intended for repeated, whole-body application over many years, modern regulatory practice expects affirmative evidence across systemic exposure, metabolism, chronic toxicity, and cumulative use. For Ethylhexyl Triazone, that evidence base remains incomplete.

Unresolved systemic exposure

Ethylhexyl Triazone is a large, highly lipophilic molecule that tends to remain within the outer layers of the skin. Laboratory and tape-stripping studies support strong stratum corneum retention, but these studies do not measure what ultimately matters for systemic risk: blood concentrations over time. One of the most important remaining data gaps for Ethylhexyl Triazone is the absence of validated human maximal-use pharmacokinetic studies, despite in vitro and modelling data suggesting low systemic availability. In the absence of this information, systemic exposure is inferred rather than measured, leaving a critical gap in the foundation of any safety assessment.

Margins of safety driven by assumptions

Current regulatory conclusions rely on calculated margins of safety derived from an oral animal study and a default assumption about dermal absorption. Numerically, that margin exceeds conventional benchmarks used in regulatory risk assessment. Scientifically, however, it remains dependent on default assumptions rather than measured human systemic exposure. Without human pharmacokinetic data and route-appropriate chronic toxicity studies, the margin cannot be considered decision-grade. It reflects mathematical convenience rather than biological certainty.

Impurities and transformation products remain unaddressed

Modern chemical regulation treats impurities and degradation products as integral to safety, not peripheral issues. Ethylhexyl Triazone lacks a harmonised pharmacopeial monograph and has no publicly available impurity qualification package aligned with contemporary standards. Public patent literature identifies potential synthesis-related impurities that have not undergone formal toxicological qualification for chronic dermal exposure.

In parallel, recent research shows that when Ethylhexyl Triazone encounters chlorinated water, it can form transformation products that exhibit greater toxicity to aquatic organisms than the parent compound in laboratory studies. These transformation pathways were not considered in historical approvals and expand the hazard landscape beyond the original molecule.

Environmental presence and continuous exposure

Ethylhexyl Triazone has been detected in marine sediments and, more recently, in indoor dust and air. This indicates environmental persistence and population-wide background exposure unrelated to intentional sunscreen use. While environmental detection alone does not define human health risk, it reinforces the importance of understanding cumulative exposure, especially for children and other high-contact groups. Current risk models do not integrate these pathways.

A cautious international posture

No major regulator has issued a contemporary, affirmative safety determination for Ethylhexyl Triazone based on modern data requirements. Some jurisdictions continue to rely on legacy opinions, while others have withheld approval pending submission of human pharmacokinetic, carcinogenicity, and endocrine data. This divergence reflects uncertainty, not consensus, and underscores the unfinished nature of the safety assessment.

The purpose of the current regulatory review

Questions have been raised regarding whether Ethylhexyl Triazone’s permitted use in Australia should be revisited in light of the absence of modern data such as human pharmacokinetics, despite the TGA’s current low-risk classification. This action does not assert that harm has been proven, nor does it challenge the public health value of sunscreen. It addresses a narrower and more fundamental issue: whether continued approval can be justified when decision-critical data remain absent.

Broader implications for sunscreen regulation

Revisiting Ethylhexyl Triazone reflects a broader shift in how long-standing ingredients are evaluated as scientific standards evolve. It highlights the difference between performance and safety, between historical acceptance and contemporary evidence. Addressing these gaps transparently supports public confidence that products used daily are regulated on the basis of current knowledge rather than legacy assumptions.

A path forward

Effective sun protection does not depend on any single chemical filter. Well-formulated sunscreens based on non-nano zinc oxide are already widely available and provide broad-spectrum UVA and UVB protection with high photostability and minimal systemic uptake through intact skin. The current review process is focused on aligning regulatory decisions with modern evidence expectations, ensuring that sunscreen protection and chemical safety progress together rather than in opposition.

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About the Australian Sunscreen Council

The Australian Sunscreen Council (ASC) is dedicated to protecting public health by championing the highest standards in sunscreen safety, testing, use and transparency.

Our mission is to ensure that all sunscreen and related products available to Australians meet or exceed the latest scientific evidence on ultraviolet (UV) protection and human health.

We promote balanced, evidence-based sun safety guidance, recognising that sunscreen is only a small part of the overall picture when it comes to sun safety and health. Our approach is holistic: effective UV protection includes shade, clothing, behaviour, and thoughtful timing of exposure—not sunscreen alone.

The ASC also supports greater public awareness of the documented benefits of moderate sun exposure, including vitamin D synthesis, improved mental wellbeing, and nitric oxide release—a process linked to healthier cardiovascular function and improved blood pressure regulation. We believe Australians deserve clear, science-backed advice that helps them understand how to obtain these benefits safely.

The ASC works collaboratively with government agencies, dermatologists, and public health experts to improve sunscreen standards and to support balanced, science-driven sun safety advice for all Australians.

Learn more at www.australiansunscreencouncil.org