The use of heat styling appliances is a rapidly growing segment within the hair care market. However, despite significant levels of academic investigation into the impact of high temperature on the structure and mechanical properties of the hair fibre, the industry does not yet have a standardized method of heat damage measurement to enable consumers and independent evaluation laboratories to objectively compare the performance of different heat styling tools. We discuss the available experimental methods to support such a standardized method and conclude that the well-established approach of measuring single-fibre tensile strength provides the best option. We then explore the sensitivity to heat damage of the various wet and dry single-fibre tensile parameters in order to identify the optimal combination for inclusion in our hair damage metric. Using the selected combination of 8 different wet single-fibre tensile strength parameters, we now propose a robust, reproducible and consumer-relevant 6-point heat damage scale. We demonstrate the relevance of the new damage scale to a range of on-market heated hair straighteners and explore the human perception of hair treated with heated straighteners delivering different damage levels according to the new scale. Based on this, we show a good correlation between the technical damage scale and the human perception of damage on hair tresses.
A few years ago, the 2-hydroxy-4´-methoxy dibenzoylmethane (DBM11) molecule was synthesized and studied as a replacement for avobenzone (AVB, butyl methoxydibenzoylmethane) because of the latter's instability under UVA radiation. These studies, conducted in absolute ethanol with an estimated UV irradiance of 8,56 mW/cm2, demonstrated almost zero decomposition of DBM11. Thus, it is a promising candidate for use as a UVA chemical filter. However, further studies must be conducted to verify its photostability once formulated into an emulsion and to establish its toxicological profile. The first aim of this work was to scale up the synthesis of DBM11 to allow its formulation into an emulsion, which is required for the evaluation of its photostability under standardized UV irradiation conditions (close to ISO 24443), as required for sunscreen testing in the cosmetic industry. Additionally, in vitro phototoxicity assessments were conducted, with slight modifications to improve reproducibility, in accordance with OECD guidelines. These results demonstrate that DBM11 exhibits promising photostability and a favourable toxicological profile, making it a potential candidate for use as a UVA filter.
Centella asiatica extract (CAE) and Marigold extract (ME) have been renowned for centuries in traditional medicine, particularly in Asia, for their wound-healing, anti-inflammatory and skin-regenerative properties. This study presents the formulation and comprehensive evaluation of serums enhanced with these extracts, aiming to harness their bioactive properties for skin health. Serums were selected over creams due to their lightweight, water-based nature, which ensures faster absorption and enhanced skin penetration of active ingredients. The serums, developed in varying concentrations (0.2%, 0.5% and 1.0%), were assessed for physicochemical properties, stability, bioactivity and skin barrier enhancement. Stability tests confirmed the serums' robustness, maintaining consistent pH (5.0–6.5), viscosity and organoleptic properties over 60 days. The MTT assay revealed that both extracts were non-cytotoxic, maintaining cell viability above 100%, with formulations containing CAE, demonstrating a concentration-dependent proliferative effect, reaching nearly 120%. Antibacterial evaluation using the agar well diffusion assay showed that both extracts exhibited considerable activity, with CAE achieving greater inhibition zones, particularly against S. aureus. Antioxidant, anti-inflammatory and anti-tyrosinase activities confirmed the strong bioactive potential of both extracts in combating oxidative stress, reducing inflammation, and regulating pigmentation. Skin barrier and permeability studies demonstrated the serums' ability to improve barrier integrity and facilitate active compound delivery. These findings demonstrate the potential of Centella asiatica and Marigold extracts for multifunctional skincare formulations, combining regeneration, hydration, antioxidant and antibacterial benefits.
Sunscreens reduce the harmful effects of ultraviolet radiation (UVR) by reflecting, absorbing or scattering photons. UVR comprises ultraviolet-B (UVB), which plays a major role in sunburn and the development of skin cancers, and ultraviolet-A (UVA), which contributes to photoaging and skin damage. The application of sunscreen is among the most effective approaches to mitigating UV-induced damage. As a topical photoprotective agent, it can be classified as either inorganic (physical blockers) or organic (chemical absorbers). Physical sunscreens are particularly beneficial for people who are hypersensitive to UVA and visible light, such as those who have photosensitising diseases. Chemical sunscreens that selectively absorb UVB and/or UVA, include cinnamates, benzophenones, benzimidazoles and dibenzalacetone (DBA). DBA is a synthetic compound with potent UV-absorbing properties, making it an important component in sunscreen formulations for effective skin protection. This review provides a comprehensive analysis of DBA, focusing on its physicochemical properties, conventional synthesis methods and structural characterization using UV–Visible absorption spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Gas Chromatography–Mass Spectrometry (GC–MS) and Nuclear Magnetic Resonance (NMR) spectroscopy. Furthermore, its potential applications in sunscreen formulations and other biological activities are critically investigated.
Determination of the sunburn protection provided by a sunscreen product is required globally for sales of these products. Over the past 80 years, many aspects of determining the protection ‘factor’ have evolved and been modified, with varying levels of impact on the sunburn protection factor (SPF) value. In order to compare new non-invasive and in vitro methods against traditional SPF test protocols, a large, multi-center clinical trial was conducted to establish the level of equivalence of these new methods with the current codified testing standard ISO24444 ([1]: Cosmetics – sun protection methods – in vivo determination of the sun protection factor (SPF), 2019). This report reports the variability found in the in vivo determination of SPF values.
Thirty-two products of varying levels of sunburn and UVA protection, in a variety of formulation vehicles and ultraviolet (UV) filter combinations and concentrations, were coded and sent to pre-qualified in vivo SPF testing laboratories. The products were divided into eight product groups (four products per product group). For each product group, samples were sent to four laboratories (across product groups, a total of 12 laboratories participated). Precision and trueness estimates were calculated separately for each product group. ‘Expected’ SPF values were not provided to the test laboratories. However, laboratories were informed as to whether the ‘true’ SPF was less than or greater than 25.
Interlaboratory variability for samples was proportional to the SPF of the products, with high SPF products having higher variability. Intra-laboratory variability (repeatability) was much lower than the interlaboratory variability.
This study highlights the fact that the interlaboratory variability of SPF results is considerable and is likely greater than expected by the public and regulatory bodies.
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