58 HAIR CARE


molecular integrity that keeps each strand strong and radiant over time.


The Global Warming Hair Protection Assay Building on this understanding, the Global Warming Hair Protection Assay leverages tryptophan fluorescence as a precise indicator of cumulative heat-induced damage. By simulating months of elevated environmental temperatures, the assay monitors the gradual decline in tryptophan signal, providing a quantitative measure of protein degradation and structural compromise. The assay captures the gradual erosion of


protein integrity that occurs long before damage becomes visible, offering a window into the molecular processes underlying hair ageing. This approach allows researchers to evaluate the protective efficacy of hair care formulations under conditions that closely mimic real-world exposure, rather than relying solely on short-term or acute stress tests. In doing so, the assay not only quantifies how


environmental heat affects hair integrity over time but also enables the development of innovative ingredients designed to preserve strength, resilience, and overall hair longevity. By linking structural-level insights to practical


product performance, the assay provides a roadmap for designing hair care solutions that actively protect and maintain hair health against the cumulative stresses of a warming environment.


Tress testing To evaluate the protective effects of test formulations, hair tresses of varying shades and types were included in the overall study to capture differences in response to heat. For the purpose of this discussion, we will focus on brunette hair tresses to present the data concisely, while still providing meaningful insight into protein protection across treated and untreated fibres. Brunette hair tresses were collected and


assigned to one of the conditions outlined in Table 1; two tresses received base shampoo and conditioner, one tress was treated with 2.0% Test Ingredient in base shampoo and conditioner, and one tress was left untreated as a control. Treatments were applied at a


dose of 0.2g of product per gram of hair twice weekly throughout the six-month heat exposure period. Following each application, hair was allowed to fully air dry before being placed in an oven set to 50°C, with tresses hung in a natural position and spaced apart to ensure consistent heat exposure. Samples were collected at one,


three, and six months to monitor changes in tryptophan fluorescence and track cumulative protein degradation over time. Tryptophan was extracted from


each hair tress by dissolving the hair in a 2 M sodium hydroxide


PERSONAL CARE MAGAZINE March 2026


TABLE 1: DESCRIPTIONS OF THE CONDITIONS AND TREATMENTS FOR EACH HAIR TRESS Condition


Untreated Control Wash Control Heat Control


2% Test Ingredient


Product None


Base Shampoo and Base Conditioner Base Shampoo and Base Conditioner


2% Test Ingredient in Base Shampoo and Conditioner


(NaOH) solution at a 1:1 ratio of hair to NaOH. After sitting for 24 hours, the solutions were filtered, and 200 µL of each extract was added in duplicate to a 96-well black side/clear bottom plate. Fluorescence was measured at excitation and emission wavelengths of 290 nm and 355 nm, respectively. Tryptophan degradation was evaluated based on changes in relative fluorescence compared to the untreated control. Three independent experiments were performed, with conditions tested in duplicate, and average values were recorded. Data were analysed using a one-way ANOVA, with statistical significance accepted at p ≤ 0.05. Percent change in tryptophan was calculated for each treatment group to quantify the protective effect of the formulations.


Results The results showed the Wash Control exhibited slight reductions in tryptophan over time while the Heat Control experienced large reductions. Tresses treated with Test Ingredient at 2.0% in shampoo and conditioner demonstrated minimal changes in tryptophan over time. As shown in Figure 1, brunette hair tresses


treated with the Wash Control experienced slight decreases in tryptophan over the six-month period compared to the Untreated Control, indicating that washing alone can partially reduce amino acid content over time. In contrast, the brunette tresses exposed to


Treatment Description


No Washes; No Heat Exposure Washes; Heat Exposure Washes; Heat Exposure


Washes; Heat Exposure


heat without protective treatment (Heat Control) exhibited substantial reductions in tryptophan of 17% and 22% after three and six months, respectively, compared to the Untreated Control, and were significantly more damaged than the Wash Control at all time points. Treatment with 2.0% Test Ingredient effectively


preserved amino acid integrity, showing minimal reductions of 0%, 5%, and 13% at one, three, and six months, respectively, relative to the Untreated Control. Notably, after six months, the tryptophan


levels in Test Ingredient–treated tresses were significantly higher than those in the Heat Control group, demonstrating that this formulation provides robust protection against prolonged exposure to extreme heat. These findings highlight the ability of Test


Ingredient to maintain protein stability and protect brunette hair from cumulative environmental stress, supporting its role in preserving hair strength, structure, and longevity. Rising global temperatures are creating


unprecedented challenges for hair health, exposing both scalp and fibre to chronic heat stress that accelerates protein degradation, moisture loss, and structural fatigue. Unlike transient thermal styling, environmental


heat represents a persistent, low-grade stressor, a form of chronic exposure that quietly undermines hair integrity over time. The Global Warming Hair Protection Assay provides a powerful, time- resolved framework to study this process, capturing the cumulative effects of heat at a molecular level.


Leveraging tryptophan fluorescence By leveraging tryptophan fluorescence as a sensitive and quantifiable indicator of protein degradation, this assay offers unique insight into how oxidative stress and sustained thermal load alter the fundamental architecture of hair. These findings underscore that in a warming world, understanding and mitigating cumulative


environmental stress is no longer


optional but rather it is essential for maintaining hair health and longevity over a lifetime. Through this lens, we can


observe not only the damaging impact of prolonged heat exposure but also the measurable


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