Objective Measurement of Minimal Erythema and Melanogenic Doses Using Natural and Solar-simulated Light¶

Abstract

Very little information exists on the amount of natural and artificial UV light required to cause sunburn and tanning in individuals with very pale skin who are at the greatest risk of developing skin cancer. We have investigated minimal erythema dose (MED) and minimal melanogenic dose (MMD) in a group of 31 volunteers with Fitzpatrick skin types I and II using an Oriel 1000 W xenon arc solar simulator and natural sunlight in Sydney, Australia. We measured the erythemal and melanogenic responses using conventional visual scoring, a chromameter and an erythema meter. We found that the average MED measured visually using the artificial UV source was 68.7 ± 3.3 mJ/cm2 (3.4 ± 0.2 standard erythema doses [SED]), which was significantly different from the MED of sunlight, which was 93.6 ± 5.6 mJ/cm2 (P < 0.001) (11.7 ± 0.7 SED). We also found significant correlations between the solar‐simulated MED values, the melanin index (erythema meter) and the L* function (chromameter). The average MMD (obtained in 16 volunteers only) using solar‐simulated light was 85.6 ± 4.9 mJ/cm2, which was significantly less than that measured with natural sunlight (118.3 ± 8.6 mJ/cm2; P < 0.05). We mathematically modeled the data for both the chromameter and the erythema meter to see if we were able to obtain a more objective measure of MED and differentiation between skin types. Using this model, we were able to detect erythemal responses using the erythema index function of the erythema meter and the a* function of the chromameter at lower UV doses than either the standard visual or COLIPA methods.

Melanin differentially protects from the initiation and progression of threshold UV‐induced erythema depending on UV waveband

“…Our results are in keeping with past studies that have found that skin reflectance measurements of pigmentation correlate with ssUV MED in normal individuals (13,16,17) and narrowband-UVB MED (311 nm TL-01) in psoriatic patients (10). Broadband UVB MED studies have shown conflicting results, with some showing a correlation (12,14,22), while others have not (6,7).…”

“…The erythema index (EI) was calculated by comparing the amount of reflected light at 546 nm, which is inversely proportional to the amount of haemoglobin or blood content in the superficial dermis, with a reference signal at 632 nm to compensate for skin tone. Dose responses for erythema have been previously quantified with an erythema meter (7,(16)(17)(18) or chromameter (6, 18) using linear regression.…”

“…The use of reflectance spectroscopy to quantitate skin erythema has also allowed the calculation of erythema dose-response gradients to UV as an alternative measure of erythemal sensitivity to UV. Similar to using MED as an endpoint for UV erythemal sensitivity, erythema dose-response gradients also seem to correlate poorly with skin type (7,15,16), and yet correlate well with skin reflectance measures Abbreviations: ANOVA, analysis of variance, EI, erythema index, MED, minimal erythema dose, MI, melanin index, ssUV, solar-simulated ultraviolet radiation, UV, ultraviolet radiation. of pigmentation (6,7,17,18).…”

Approaches to Document the Efficacy and Safety of Microdermabrasion Procedure

“…The L à and b à values have been used extensively to study changes in melaninderived color. [11][12][13] Our results showed a decrease in yellow color corresponding to a lightening of hyperpigmented areas (b à value) and an increase in skin brightness (L à value), with a significant improvement as early as after the first treatment. The increase in brightness was recorded throughout the study, although at Week 6 it failed to reach significance (p = 0.0654).…”

Digital dermoscopy to determine skin melanin index as an objective indicator of skin pigmentation

“…While several studies reported the use of colorimetry [4,9] and spectrophotometry [10] to assess SPT, Pershing et al used spectrophotometry to objectively determine all six SPTs using only constitutive skin color independent of UVL-induced erythema [2] . The "gold standard" method of assessing skin pigmentation is spectrophotometry; however, it is difficult to perform spectrophotometry under clinical conditions.…”