The oil, extracted from unroasted coffee beans, is used in cosmetics as it can contribute to the skin barrier and to improve hydration, and also has the capacity to absorb UVB radiation, as well as protective properties.
A research team made up of colleagues in Portugal and Brazil decided to further research the safety of the ingredient, as despite its use there are insufficient studies about its safety when applied in cosmetic formulations.
Given that GCO possesses skin care properties and that it is a sustainable resource, the aim of this study was to conduct an integrated approach that combines in vitro cell culture assays and in vivo studies conducted in humans using biophysical techniques to assess the skin compatibility of formulations containing it.
“The results obtained in the study indicate that GCO seems to be safe for topical applications and showed good skin compatibility under the experimental conditions of the study,” says the study.
In their research, the scientists used the MIT reduction assay in human keratinocytes to evaluate the cytotoxicity of GCO and of formulations containing 2.5–15% GCO.
Formulations containing 15% of the ingredient and the vehicle were applied under in use conditions in the volar forearm of human volunteers over the course of three days, with transepidermal water loss (TEWL), stratum corneum water content and erythema index evaluated every 24 hours, using biophysical techniques.
The same formulations were probed for skin tolerance through a patch test.
The study found that neither the pure oil nor any of its formulations showed any cytotoxic effects and none of the volunteers exhibited any reaction to the application of GCO formulation.
“These results seem indicative of the good skin compatibility of this ingredient in cosmetic formulations,” note the researchers.
TEWL values showed a slight reduction when the formulation containing GCO was applied. Stratum corneum water content and erythema index did not show significant differences, as the results observed in the first day of the study were maintained throughout 3 days.