Science
Mechanism of Action
Homosalate, an organic compound categorized as a salicylate, functions by absorbing incident ultraviolet (UV) light. It specifically targets short-wave UVB rays, primarily within the 295-315 nm range, with peak absorption at 306 nm. Upon absorbing UV radiation, its molecules undergo a structural transformation, converting the high-energy UV into less damaging infrared radiation (heat), thus preventing direct cellular damage.
Research
Clinical Evidence
Medium confidenceN/A
Key findings
- 01 When tested alone, a 10% concentration provided an SPF of 4.3, demonstrating limited standalone protection. It also showed a 10% reduction in SPF efficacy within 45 minutes, indicating insufficient photostability.
- 02 In comprehensive sun protection products, concentrations up to 10% have been shown to contribute to achieving SPF values ranging from 10 to 50, highlighting its utility in combination with other filters.
- 03 The SCCS concluded that Homosalate is safe as a UV-filter in face cream and pump spray products at concentrations up to 7.34%.
Transparency
Dusting Analysis
Homosalate's inherent limitations in standalone SPF efficacy (10% yields only SPF 4.3) and photostability necessitate its co-formulation with other UV filters and stabilizers to achieve robust sun protection. Its use up to 10% in sun protection products is strategic for comprehensive SPF, not indicative of 'dusting' or excessive, ineffective inclusion.
The Formula
Formulation
Stability
Homosalate exhibits pH-dependent stability, degrading more rapidly under basic conditions; its half-life is significantly reduced to 69.7 hours at pH 9, compared to approximately 210-215 hours at pH 4-7. It is not intrinsically photostable, requiring combination with other UV filters and co-formulation with photostabilizers (e.g., octocrylene) to maintain its protective performance.
Synergies
- Other UV filters (for broad-spectrum protection and enhanced stability)
- Photostabilizers (e.g., octocrylene)
Conflicts
- Basic pH conditions (leads to hydrolysis and accelerated degradation)
Safety
Safety Profile
Regulatory maximum concentration limits for Homosalate vary by region. The FDA approves its use up to 15% as a Category 1 UV filter. In contrast, the SCCS initially deemed it unsafe above 10% for general cosmetic use, subsequently advising a maximum concentration of 0.5% in the final cosmetic product, with an exception for face creams and pump sprays where up to 7.34% is considered safe. In-vitro studies suggest potential estrogenic activity, though this has not been substantiated in human studies under real-world usage. The SCCS regards evidence for endocrine disrupting properties as inconclusive and equivocal. Homosalate is considered to have a low risk of skin irritation and sensitization.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Homosalate is a valuable UVB filter for sun protection, best integrated into multi-UV filter formulations to address its inherent photostability limitations and achieve comprehensive, stable SPF efficacy within established safety limits.
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