# A multimodal approach to acne mechanica associated to medical face masks using clinical examination, fluorescent photography, and in vivo reflectance confocal microscopy

## TL;DR

This study explores how medical face masks cause acne by comparing skin changes in different facial areas using multiple imaging techniques.

## Contribution

The study introduces a multimodal approach combining clinical, fluorescent, and microscopic methods to analyze acne from face masks.

## Key findings

- The glabella showed more UV fluorescent spots and larger affected areas compared to the cheek-chin junction.
- The cheek-chin junction had higher rates of hyperkeratotic follicles and inflammation, suggesting mechanical irritation.
- Perifollicular stratum corneum was thinner in the cheek-chin junction, indicating structural differences in affected regions.

## Abstract

With yet unclear pathogenesis, acne mechanica associated to medical face masks(MFM) gained increased attention during the COVID-19 pandemic. Between November 2021-January 2022 we conducted an exploratory, cross-sectional study evaluating the differences between the glabella and cheek-chin junction using clinical examination, fluorescent photography (FP), videodermatoscopy and in vivo reflectance confocal microscopy (RCM). Medical doctors from our country and 6th year medical students were invited. Participants self-identified as consistent MFM users during work hours. We analysed 19,432 images from 14 consecutive subjects, 11 females, 3 males, mean age,29.93 years (SD = 4.69). Clinical examination revealed more inflammatory lesions on the cheeks and chin (+ 9.35;95%CI + 2.31to + 16.39;d = 0.76, P =.01). FP considered ultraviolet red fluorescing spots(UVRFs) from the glabella and the cheek-chin junction, with significantly more spots in the former (+ 5.43;95%CI + 2.64to + 8.20; d = 1.12; P =.001). The average area in mm2 covered by the spots was significantly larger in the glabella (+ 3.26;95%CI + 1.43to + 5.08;d = 1.02; P =.002). RCM considered 9546 follicles, 4966 from the glabella, and 4580 from the cheek-chin junction. The cheek-chin junction had a significantly higher proportion of hyperkeratotic follicles than the glabella (+ 9%;95%CI + 2%to + 16%;d = 0.79;P =.01). In the dermal-epidermal junction, the cheek-chin region had a significantly higher proportion of follicles with signs of inflammation than the glabella (+ 10%;95% CI + 3%to + 18%; d = 0.80; P =.010). Perifollicular stratum corneum thickness was significantly lower in the cheek-chin junction, 19.56 μm (SD = 4.84) compared to the glabella, 24.25 μm (± 4.93) (-4 μm;95% CI-1 μm to– 8 μm; r =.88; P =.01). The distribution of UVRFs, known to correlate with microbial activity and sebum production, is similar to pre-pandemic studies, suggesting that in acne mechanica associated to MFM, follicular hyperkeratinisation, inflammation, and irritation, may outweigh other possible alterations.

The online version contains supplementary material available at 10.1007/s00403-025-04104-2.