Skin Res Technol. 2019;1–5. wileyonlinelibrary.com/journal/srt | 1 © 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 1 | INTRODUCTION The perceived skin color is the net result of selective absorption and scattering of specific wavelengths. Chromophores absorb light; they can be epidermal such as melanins and carotenoids, or dermal such as hemoglobins and bilirubin. Meanwhile, the main scattering struc- tures in the skin are keratohyaline granules and collagen bundles in the epidermis and dermis respectively. 1 Other factors are also in- volved in the determination of the perceived skin color; these include microcirculation, surface roughness or scaliness, sweat and sebum secretion, 2 and the transparency of the stratum corneum. 3 Melanin is undoubtedly the major determinant of skin color. However, similar to melanin, hemoglobin in dermal capillaries can also attenuate light and this needs to be considered when assessing pigmentation. 4,5 Objective assessment of skin color has become of paramount im- portance in the management of pigmentary disorders. 6 Accordingly, several objective, non-invasive instruments are currently available for precise measurement of skin color. 5 These instruments are either Received: 7 December 2018 | Accepted: 12 January 2019 DOI: 10.1111/srt.12680 ORIGINAL ARTICLE Evaluation of different factors influencing objective measurement of skin color by colorimetry Tag S. Anbar 1 | Amira A. Eid 2 | Mohamed T. Anbar 3 1 Department of Dermatology, Andrology and STDs, Faculty of Medicine, Minia University, Minia, Egypt 2 Department of Dermatology, Venereology and Andrology, Faculty of Medicine, Alexandria University, Alexandria, Egypt 3 Department of Dermatology and Venereology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt Correspondence Amira A. Eid, Department of Dermatology, Venereology and Andrology, Faculty of Medicine, Alexandria University, Alexandria, Egypt. Emails: amira.eid@alexmed.edu.eg; dramiraeid@yahoo.co.uk Abstract Background: Objective determination of skin color has become an essential require- ment in managing pigmentary disorders including vitiligo. The readings of available devices can be influenced by factors such as surrounding temperature, vasodilation/ constriction, and skin surface properties. Our aim was to investigate the influence of hair color and length, skin stretching, incomplete contact of the device with the skin, and the pressure with which the device is applied to the test area on skin color determination. Materials and methods: Dermacatch® was used to determine the influence of hair color and length in 30 vitiligo patients, and of wrinkles, incomplete contact of the device with the skin and pressure of the device on the test area in 30 healthy volun- teers on melanin and erythema indices measured by the device. Results: Melanin index was significantly higher in lesions with black hair compared to lesions with white hair (P < 0.001) and the MI significantly decreased when the black hair was shaved (P < 0.001) and when the skin over the test area was stretched (P < 0.001). Incomplete contact of the device with the test area led to significantly higher MI (P < 0.001) and lower EI (P < 0.001). Meanwhile, high pressure induced by the device on the test area led to significantly lower MI (P < 0.001) and significantly higher EI (P < 0.001). Conclusions: Factors influencing the readings of devices used for objective determi- nation of skin color have to be taken consideration to ensure accuracy of the meas- urements done. KEYWORDS colorimetry, erythema index, melanin index, vitiligo