Facial Toner Containing 2% Arbutin and 3% Niacinamide Improves Pore Appearance, Uneven Skin Texture, and Skin Brightness Measured by Individual Typology Angle

2. Materials and Methods

2.1. Test Material

In this study, we tested the efficacy of a facial toner containing 2.0% (w/w) Arbutin and 3.0% (w/w) Niacinamide (Good Molecules Niacinamide Brightening Toner, hereafter referred to as “Facial Toner”), which had been previously assessed for topical safety in a Human Repeat Insult Patch Test (HRIPT) with fifty-five healthy adult volunteers. The HRIPT resulted in no irritation or sensitization events. The test formulation also contains Water (q.s.p. 100% w/w), Glycerin (6.7% w/w), 1,2-Hexanediol (2.2% w/w), Propanediol (2.0% w/w), Betaine (0.5% w/w), Glycyrrhiza Glabra (Licorice) Root Extract (0.1% w/w), 3-O-Ethyl Ascorbic Acid (0.1% w/w), Ethylhexylglycerin (0.1% w/w), Carbomer (0.06% w/w), Tromethamine (0.04% w/w), Trisodium Ethylenediamine Disuccinate (0.02% w/w), Theobroma Cacao (Cocoa) Seed Extract (35 ppm w/w), Sodium Hyaluronate (15 ppm w/w), Dextrin (15 ppm w/w), and Tocopherol (10 ppm w/w).

2.2. Dermatological Clinical Efficacy Study

This clinical efficacy study was a longitudinal, open-label, monadic, home-use, 4-week clinical study investigating the efficacy of the Facial Toner containing 2.0% (w/w) Arbutin and 3.0% (w/w) Niacinamide in volunteers with expert-assessed visible/large pores and self-declared uneven skin texture. This study was sponsored by Good Molecules, LLC, USA, and conducted in the United States of America by a contract research organization (Validated Claim Support, LLC, USA) between October and November 2023. The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board Allendale Investigational Review Board, Inc. (IRB Study Number: CS231034). All volunteers signed a written informed consent before initiating the study. Volunteers willing to be photographed signed a model release agreement consenting to use of their images.

Volunteers were included if they were of legal age, healthy, had expert-assessed visible/large pores (score of > 3 on a 10-point scale at baseline), and had self-declared uneven skin texture, and were willing to comply with the procedures, methods, evaluations, and study product usage described in the informed consent document. Volunteers were excluded if they were historically allergic to facial products; pregnant or breast-feeding; immunocompromised; presented observable pre-existing facial skin disease or condition; a history of severe or chronic diseases and conditions such as cancer, AIDS, insulin-dependent diabetes, renal impairment, mental illness, and/or drug/alcohol addiction; a history of melanoma, or treated skin cancer within the last five years; a history of taking hormones within the previous three months; a history of use of oral contraception for less than three months before the study or who have changed their contraceptive method within three months before the study; have regular salon and/or dermatological procedures (microdermabrasion, fillers, facial peels, etc.) and are not willing to stop throughout the study; and if they were currently participating in other clinical trials involving testing a facial product.

After screening and recruitment, thirty-one healthy adult volunteers completed the study. They underwent an approximate five-day washout period in which they discontinued skincare products. Then, they were instructed to apply one dropper (1 mL) of the Facial Toner onto a cotton pad and gently sweep over clean skin twice daily, in the morning and at night, for four weeks. The Facial Toner was not washed off since toners are designed to be left on the skin to be absorbed before applying the rest of the skincare routine, such as serums, creams, and sunscreen. Volunteers were also required to apply the supplied SPF 30 during the daytime. The instructions were explained and provided to all volunteers verbally and in writing, along with a daily product log to record use to ensure compliance during home use. Daily logs were reviewed in week four, and test material containers were weighed to verify protocol compliance with product use instructions.

Variations in the appearance of pores (Pore Appearance), skin brightness (Radiance/Luminosity), and uneven skin texture (Skin Texture/Smoothness) were followed up and evaluated objectively by trained expert grading at baseline (week zero) and week four utilizing a 10-point ordinal scale (Table 1), overhead lighting, and a lighted magnifying loop as needed.

Digital photographs at baseline and week four also helped to subjectively determine variations in the appearance of pores, skin brightness, and uneven skin texture. Photographs were not retouched. At week four, consumer perception of the product and its effects was determined by analyzing results from a self-perception questionnaire using a 4-point Likert scale.

Facial skin brightness was measured by the Chroma Meter CR-200 (Konica Minolta, Tokyo, Japan), which converts all colors within the range of human perception into a standard numerical code known as the CIEL*a*b* color space (defined by the International Commission on Illumination, abbreviated CIE in French), allowing quantification of product-induced changes in skin color within these parameters for analysis. The Chroma Meter represents lightness as L* where 0 = black and 100 = white. At the same time, the red-green and yellow-blue color spectra are defined as a* and b*, respectively, where red and yellow are indicated by positive values and green and blue by negative values. All volunteers had Chroma Meter measurements taken in triplicate on the right or left cheek, per randomization, at baseline and week four. With Chroma Meter measurements, the Individual Typology Angle (ITA°) was calculated for each individual per the equation [15]:

$$ITA°=\left(ArcTangent\right({\displaystyle \frac{L\mathrm{*}-50}{b\mathrm{*}}}\left)\right)\times {\displaystyle \frac{180}{\pi }})$$

ITA° is an objective classification of skin color into six groups ranging from very light to dark [16]. The smaller the ITA° value, the darker the skin type. The values of ITA° per skin subtype are as follows: the very light skin subtype is an ITA° > 55°, the light subtype has the range 41° < ITA° ≤ 55°, the intermediate subtype ranges 28° < ITA° ≤ 41°, the tan subtype range is from 10° < ITA° ≤ 28°, the brown subtype has the range -30° < ITA° ≤ 10°, and the dark subtype is an ITA° ≤ -30°. Results on week four were compared to the baseline. An n = 30 volunteers was used for the final Chroma Meter data analysis. One of the volunteers’ Chroma Meter data was removed due to a suspected measurement or data entry error in week four.

2.3. Statistics

Mean, minimum, and maximum statistics are provided for age. Frequency (expressed as number and percent) is provided for ethnicity and race. A paired t-test was used to compare variations from week four to the baseline and determine any significant differences in the instrumental assessments and expert grading. All statistical tests were set to a significance level of 5%. Mean, standard deviation (SD), and mean percent change compared to baseline values and percent of volunteers showing improvement are provided for the week four timepoint. Frequency (expressed as number and percent) and favorable response threshold (≥ 50% agreement amongst volunteers characterizes a favorable response) were used to interpret the subjective questionnaire. R Studio Version: 2024.04.2+764 (Posit, PBC, United States of America) was used for general statistics and paired t-test of the ITA° and L* measurements. The RStudio package ggplot2 was used to generate graphs. The raw data supporting the conclusions of this article will be made available by the authors on request.