Elsevier

Methods

Volume 28, Issue 1, September 2002, Pages 14-19
Methods

Ultraviolet radiation-induced erythema in human skin

https://doi.org/10.1016/S1046-2023(02)00205-0Get rights and content

Abstract

We have evaluated UVR-induced erythema in previously unexposed buttock skin of volunteers of skin types I, II, III, and IV. Studies were done with solar-simulated radiation (SSR), UVB, and UVAI and we determined the just perceptible minimal erythema dose (MED) and, in some cases, quantified erythema with a reflectance device. The results show that there is a trend for increased SSR MED with skin type, with the MED of skin type IV being approximately twice that of skin type I, a smaller difference than one might have expected. However, there is a very considerable overlap of MED between skin types which shows that MED is a very poor indictor of skin type. Quantitative dose–response and time course studies with SSR and UVAI showed broadly similar responses when comparable MED-based exposures were given. We used our data to test the new concept of the standard erythema dose (SED) with two different erythema action spectra, and confirmed that the SED approach works with the different UVR sources that we studied.

Introduction

Erythema, or skin redness caused by inflammation, is the most widely used clinical endpoint in human skin photobiology. Erythema is also used in determining the sun protection factor (SPF) of sunscreens. Despite its widespread use, we know little of the basic biology of ultraviolet radiation (UVR)-induced erythema and the reader is referred to a review by Clydesdale et al. [1].

Individual sensitivity to UVR is assessed by the minimal erythema dose (MED), most often 24 h after irradiation. The MED is defined as the lowest UVR dose that will cause either a just perceptible redness or redness with a definite border. One study has shown that the former definition is more reliable [2].

The MED is judged by eye after a predetermined UVR dose series has been given to the individual in question. However, this subjective approach, in which the MED is a threshold in a dose–response curve, discards a large amount of potentially valuable data. The eye, although excellent at assessing threshold responses, is poor at the quantification of color. The best that can be done is semiquantitative grading such as +, ++, +++. The development of reflectance devices such as the Dia-Stron erythema meter enables the quantification of erythema and the construction of dose–response curves [3], [4], [5]. Erythema meters work by measuring the decreased green reflectance, relative to red, from hemoglobin in dermal blood vessels [3], i.e., the change in green to red ratio.

Several workers have determined action spectra (relative effectiveness at different wavelengths) for the MED in human skin [6], [7], [8], [9] using “monochromatic” radiation, in reality narrow- to broad-spectrum radiation, from a monochromator. Some of the earlier studies have been pooled to generate a reference erythema action spectrum that has been adopted by the Commission Internationale de l'Eclairage (CIE) [10]. These studies show that UVB (280–315 nm) is orders of magnitude more effective per unit dose (J/m2) than UVA (315–400 nm). For example, the median MED at 300 nm is 0.025J/cm2 whereas that at 360 nm is 32J/cm2 [9]. A comparison of the action spectra for erythema and epidermal DNA photodamage provides strong circumstantial evidence that DNA is a major chromophore for erythema [9]. The Anders et al. [7] action spectrum, determined from truly monochromatic laser radiation, shows a secondary peak at 362 nm, which is strongly indicative of an additional chromophore for UVAI (340–400 nm) erythema and is almost certainly mediated via reactive oxygen species.

The MED is a measure of individual sensitivity to UVR. Recently, a new term, the standard erythema dose (SED), has been proposed [11]. The SED is a fixed dose of 100J/m2 that is biologically weighted by the CIE erythema action spectrum [10] and the emission spectrum of the UVR source. Thus, the SED is independent of the emission spectrum of the UVR source.

Our laboratory has had considerable experience in the assessment of human erythema with different UVR sources and in different skin phototypes. This article describes our protocols, data analysis, and interpretation. We have also transformed our MED data to SED to assess the value of the SED concept. The data come from a variety of studies, all of which had approval from the local ethics committee.

Section snippets

Volunteer selection

Volunteer selection was based on the Fitzpatrick phototype [12]. Complexion, ability to tan, and capacity to sunburn in summer sunlight were all taken into consideration by interview and questionnaire when assigning skin type.

Dosimetry and UVR sources

Emission spectra and irradiances were determined with a DM150BC double-monochromator spectroradiometer (Bentham Instruments, Reading, UK) using an integration sphere and gratings blazed at 250 nm. The spectroradiometer was calibrated using a deuterium lamp that had been

Results

Most of the data are plotted as a function of MED and SED using either the CIE [10] or the Anders et al. [7] erythema action spectrum. The former covers the entire range of the SSR source whereas the latter does not provide data beyond 374 nm.

Concluding remarks

We believe that our data confirm the importance of quantifying the erythema response [3], [4], [5] and that this can be readily done with an instrument such as the Dia-Stron erythema meter. The erythema response to UVR exposure may be given or expressed as a function of either biological dose (MED) or physical dose (J/m2) as shown by Kelly et al. [18]. When data are expressed as J/m2 there is a clear difference between the skin types. However, when erythema is plotted as a function of MED, the

Acknowledgements

We thank Deirdre Kelly and John Sheehan for the use of erythema data generated from their Ph.D. studies, and Professor Brian Diffey for providing us with the interpolated Anders et al. [7] action spectra data. The work described was supported by Contracts from the EC (ENV-4-CT97-0556) and the UK Department of Health (121/6379).

References (24)

  • A.R. Young et al.

    J. Invest Dermatol.

    (1998)
  • A.R. Young et al.

    J. Invest Dermatol.

    (1996)
  • G.J. Clydesdale et al.

    Immunol. Cell Biol.

    (2001)
  • A.G. Quinn et al.

    Br. J. Dermatol.

    (1994)
  • B.L. Diffey et al.

    Br. J. Dermatol.

    (1984)
  • B.L. Diffey et al.

    Br. J. Dermatol.

    (1987)
  • B.L. Diffey et al.

    Clin. Phys. Physiol. Meas.

    (1991)
  • J.A. Parrish et al.

    Photochem. Photobiol.

    (1982)
  • A. Anders et al.

    Photochem. Photobiol.

    (1995)
  • N. Kollias et al.

    Photodermatol. Photoimmunol. Photomed.

    (1996)
  • A.F. McKinlay et al.

    CIE J.

    (1987)
  • B.L. Diffey et al.

    Photodermatol. Photoimmunol. Photomed.

    (1997)
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