Cool versus warm water for facial cleansing: A randomized controlled clinical study of skin barrier, skin physiology, cleansing efficacy and water consumption

Abstract Objective To quantify the effects of water temperature and tap‐running behaviour during routine facial cleansing on skin barrier function, skin physiological parameters, make‐up‐removal efficacy and the associated water and energy consumption. Methods In a 10‐day, randomized, controlled clinical study, 52 healthy adults (46 women, 6 men; aged 19–72 years) cleansed their face daily using ELEMIS Pro‐Collagen Cleansing Balm under one of four conditions: cool or warm water, with the tap either turned off during cleansing or left running. Participants were blinded to the environmental objectives. Water usage was covertly recorded with calibrated meters on the hot and cold feed pipes. Transepidermal water loss (TEWL; Tewameter® TM 300), skin hydration (Corneometer® CM 825), skin pH (skin pH‐meter PH 905) and skin radiance and translucency (TLS‐850®, Diastron Ltd) were measured at baseline and on days 1, 2, 4, 7 and 10. Make‐up‐removal efficacy was evaluated colourimetrically following standardized light‐ and heavy‐make‐up regimens. Cumulative effects on TEWL were summarized as area under the curve (AUC) over 10 days. Between‐group differences were tested with two‐way ANOVA, the Mann‐Whitney U test and the Wilcoxon rank‐sum test; α = 0.05. Results Warm‐water cleansing used on average 27% more water per cleansing event than cool‐water cleansing ( p < 0.04). Repeated warm‐water cleansing produced a statistically significant increase in TEWL of approximately 3.4 g·m −2 ·h −1 at day 10 ( p < 0.01), consistent with impairment of barrier function, whereas cool‐water cleansing produced no significant change (Δ ≈ 1 g·m −2 ·h −1 ; p = 0.15). Cool‐water cleansing was associated with a small but statistically significant fall in skin surface pH (Δ −0.4 pH units, p < 0.02), whereas pH was unchanged with warm water. Stratum‐corneum hydration declined modestly in all groups. Make‐up‐removal efficacy did not differ significantly between water temperatures ( p > 0.05 for all colourimetric comparisons), with both regimens returning skin colour values to baseline. Conclusion Routine facial cleansing with cool water preserves skin barrier integrity, supports a more favourable skin surface pH and matches the make‐up‐removal performance of warm‐water cleansing while substantially reducing water and energy consumption. Cool‐water cleansing offers a behaviourally accessible route to combine measurable skin benefits with a reduced environmental footprint.