Objective:
To quantify the effects of water temperature and tap-running behaviour during routine facial cleansing on skin barrier function, skin physiological parameters, cleansing efficacy, and associated water and energy consumption.

Methods:
In a 10-day, randomised, controlled clinical study, 52 healthy adult volunteers (46 female, 6 male; aged 19–72 years) cleansed their face daily using a Cleansing Balm under one of four conditions: cool or warm water, with the tap either turned off or left running. Volunteers were blinded to the study’s environmental objectives. Water usage was covertly measured using calibrated meters on hot and cold feed pipes, with a thermostatic blending valve for warm water delivery. Skin barrier function (transepidermal water loss (TEWL)), skin moisturisation (Corneometer®), skin pH, radiance and translucency (Diastron TLS-850®), and facial imaging (Canfield Visia-CR®) were assessed at baseline and on days 1, 2, 3, 5, and 10. Makeup removal efficacy was evaluated using colorimetric analysis following application of both light and heavy makeup regimes. Statistical analyses included non-parametric 2-way ANOVA and Wilcoxon rank sum testing.

Results
Warm water cleansing resulted in significantly higher water consumption compared with cool water (P<0.04), with additional increases when the tap was left running. Repeated warm water cleansing caused statistically significant increases in TEWL over time, indicating impairment of skin barrier function, whereas cool water cleansing resulted in minimal TEWL changes. Area-under-the-curve analysis over 10 days demonstrated a significant overall advantage for cool water cleansing compared with warm water for TEWL (P<0.04). Skin pH was significantly lower following cool water cleansing at day 10, while warm water showed no significant change. No statistically significant differences were observed in skin moisturisation, or makeup removal efficacy between warm and cool water conditions. Cool water cleansing resulted in significantly increased skin radiance (P=0.05), whereas warm water was not significant. Environmental modelling demonstrated substantial reductions in water use and associated carbon emissions when cool water was used, particularly with the tap turned off.

Conclusion
Routine facial cleansing with cool water preserves skin barrier integrity, supports a more favourable skin pH, increases skin radiance, delivers effective cleansing performance, and significantly reduces water and energy consumption compared with warm water cleansing. This study demonstrates that environmentally conscious choices can also support improved skin condition, rather than compromising product performance.

Objective:
There is a significant consumer demand for toothpastes that help whiten teeth. Teeth staining is mostly caused by dietary habits and respective extrinsic stains formation.
Comparing different toothpastes whitening claims can be challenging due to variability in test substrate types, dimensions, inter-substrate variability, staining models, etc.
A standardized methodology that quantifies extrinsic stain removal without abrading the surface was developed, by using in-vitro Hydroxyapatite surfaces, as it is human tooth enamel main component.
Stain removal was quantified by CIELab L colour factor (white / black axis) measurements.

Methods:
Different Hydroxyapatite surfaces were tested, using coffee and Yorkshire-tea based-solutions to stain the surfaces at 37 ± 1˚C.
The number of staining cycles needed and type of surface finish (polished or rough surface) were evaluated.
The stained surfaces were brushed with a toothpaste-based dilution and DI water alone, simulating a 3-week teeth-brushing period. The toothpaste prototype used had an abrasive system comprising hydrated silica and calcium carbonate.

Results:
To enable sufficient surface staining, a surface with roughness and a total of four staining cycles were performed. This allowed for the extrinsic stains to adhere to the surfaces. If the surfaces were polished the stains didn’t adhere to the surface.
Following brushing with the diluted toothpaste-medium there was a significant increase in stains removal, as shown by surface whiteness value increase A whiteness increase from 23-129% was noted, depending on the tested surface type.

Conclusions:
In vitro whitening assessment trials by extrinsic stain removal using synthetic substrates would allow sourcing of more homogeneous test surfaces with a bigger surface area.
This laboratory methodology based using in-vitro surfaces could be used for pre-clinical trials product benchmarking screening and claims support.
Keywords
Hydroxyapatite, toothpaste, teeth extrinsic stains, in-vitro test surfaces.