Characterising the variations in ethnic skin colours: a new calibrated data base for human skin
Open accessAbstract
BACKGROUND: Accurate skin colour measurements are important for numerous medical applications including the diagnosis and treatment of cutaneous disorders and the provision of maxillofacial soft tissue prostheses. METHODS: In this study, we obtained accurate skin colour measurements from four different ethnic groups (Caucasian, Chinese, Kurdish, Thai) and at four different body locations (Forehead, cheek, inner arm, back of hand) with a view of establishing a new skin colour database for medical and cosmetic applications. Skin colours are measured using a spectrophotometer and converted to a device-independent standard colour appearance space (CIELAB) where skin colour is expressed as values along the three dimensions: Lightness L*, Redness a* and Yellowness b*. Skin colour differences and variation are then evaluated as a function of ethnicity and body location. RESULTS: We report three main results: (1) When plotted in a standard colour appearance space (CIELAB), skin colour distributions for the four ethnic groups overlap significantly, although there are systematic mean differences. Between ethnicities, the most significant skin colour differences occur along the yellowness dimension, with Thai skin exhibiting the highest yellowness (b*) value and Caucasian skin the lowest value. Facial redness (a*) is invariant across the four ethnic groups. (2) Between different body locations, there are significant variations in redness (a*), with the forehead showing the highest redness value and the inner arm the lowest. (3) The colour gamut is smallest in the Chinese sample and largest in the Caucasian sample, with the Chinese gamut lying entirely the Caucasian gamut. Similarly, the largest variability in skin tones is found in the Caucasian group, and the smallest in the Chinese group. CONCLUSION: Broadly speaking, skin colour variation can be explained by two main factors: individual differences in lightness and yellowness are mostly due to ethnicity, whereas differences in redness are primarily due to different body locations. Variations in lightness are more idiosyncratic probably reflecting the large influence of environmental factors such as exposure to sun.
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Exercise-based heart rate monitoring was most affected by skin-tone bias, while resting heart rate accuracy was generally preserved.
“When stratified by outcomes, exercise-based heart rate monitoring was most affected by skin-tone bias, while resting heart rate accuracy was generally preserved [12-14].”
From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [13]
The Results and Samples and protocol sections describe spectrophotometer measurements of skin colour, not heart-rate monitoring. Searches for exercise, resting heart rate, wearable monitoring and photoplethysmography found no passage addressing the claimed difference in accuracy. (LLM, conf=0.78)
Experimental — accuracy not yet measuredThe Fitzpatrick Skin Type Scale has large within-group variations of skin tone.
“weak correlation with skin color, and large within-group variations of skin tone4,7,8”
From Response To: Investigating sources of inaccuracy in wearable optical heart rate sensors (2021) · cites this paper as [8]
The Fitzpatrick Skin Type Scale has a weak correlation with skin color.
“weak correlation with skin color, and large within-group variations of skin tone4,7,8”
From Response To: Investigating sources of inaccuracy in wearable optical heart rate sensors (2021) · cites this paper as [8]
These pulse oximeters have probably been calibrated on a population sample with light-skin pigmentation, which miss relevant interaction effects of confounding variables and skin pigmentation.
“Besides, these pulse oximeters have probably been calibrated on a population sample with light-skin pigmentation, which miss relevant interaction effects of confounding variables and skin pigmentation [23,33,109].”
From Skin pigmentation influence on pulse oximetry accuracy: a systematic review and bibliometric analysis (2022) · cites this paper as [109]
The FST phototype designation with six categories has only a weak correlation with skin color, with large within-group variance of skin tone.
“The phototype designation with six categories has been shown to have only a weak correlation with skin color with large within-group variance of skin tone [13, 15, 16].”
From Limiting racial disparities and bias for wearable devices in health science research (2020) · cites this paper as [16]
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Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring
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- Authors
- Xiao, K., Yates, J. M., Zardawi, F., Sueeprasan, S., Liao, N., Gill, L., Li, C., & Wuerger, S.
- Affiliations
- University of Science and Technology Liaoning (CN)
- University of Manchester (GB)
- University of Sulaimani (IQ)
- Chulalongkorn University (TH)
- Beijing Institute of Technology (CN)
- Manchester Metropolitan University (GB)
- University of Liverpool (GB)
- Corresponding author
- Wuerger, S.
- Venue
- Skin Research and Technology
- Publisher
- Wiley
- Published
- 2016-06-08
- Volume
- 23
- Issue
- 1
- Pages
- 21-29
- ISSN
- 0909-752X (ISSN-L)
- 1600-0846
- OpenAlex
- W2414757500
- Cited by
- 95
- References
- 12
- Citations by year
- 2026: 6 · 2025: 12 · 2024: 11 · 2023: 6 · 2022: 11 · 2021: 16 · 2020: 11 · 2019: 12 · 2018: 7 · 2017: 1 · 2016: 2
- FWCI
- 3.47
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Skin Research and Technology (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Research Explorer (The University of Manchester) (publishedVersion, cc-by)
- White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
- Funders
- Royal Academy of Engineering (RECI033)
- Engineering and Physical Sciences Research Council (EP/K040057/1)
- National Natural Science Foundation of China (61078048)
- Topics
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Color Science and Applications
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › melanin and skin pigmentation
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Categorization, perception, and language
- Keywords
- skin colour, ethnic differences, CIELAB, skin redness, skin yellowness, skin lightness, body location, color gamut, spectrophotometry, sun exposure
- MeSH terms
- Adolescent, Adult, Aged, Calibration, Colorimetry, Ethnicity, Female, Humans, Male, Middle Aged, Sensitivity and Specificity, Skin Pigmentation, Reproducibility of Results, Databases, Factual, Young Adult
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