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Pigmentation01:19

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Pigmentation after single and multiple UV-exposures depending on UV-spectrum.

M H Ravnbak1, H C Wulf

  • 1Department of Dermatology, D92, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark. mette@ravnbak.dk

Archives of Dermatological Research
|January 27, 2007
PubMed
Summary

Minimal pigmentation dose (MMD) after UV exposure varies with skin type and UV wavelength. Pre-exposure pigmentation is a better predictor of MMD than skin type, especially for UVA1. Shorter wavelengths require higher doses for MMD.

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Area of Science:

  • Dermatology
  • Photobiology
  • Skin Physiology

Background:

  • Minimal pigmentation dose (MMD) after single UV exposure is well-studied, but data on multiple exposures across diverse skin types is limited.
  • Previous research primarily focused on fair-skinned individuals, leaving a gap in understanding MMD variation in more pigmented skin.
  • Investigating MMD after repeated UV exposure is crucial for accurate photoprotection guidelines and understanding skin's response to sunlight.

Purpose of the Study:

  • To determine the minimal pigmentation dose (MMD) one week after single and five UV exposures.
  • To assess MMD across a wide range of constitutive pigmentation (Skin Types II-V).
  • To compare the efficacy of different UV sources (Solar Simulator, narrowband UVB, broadband UVA, UVA1) in inducing pigmentation.

Main Methods:

  • Recruited 52 volunteers with Skin Types II-V.
  • Quantified skin pigmentation using reflectance spectroscopy.
  • Administered UV exposures (Solar Simulator, UVB, UVA, UVA1) over 1 and 5 days, determining MMD one week post-exposure.

Main Results:

  • Higher UV doses were required for MMD in more pigmented skin for most sources, except UVA1.
  • A positive linear correlation between UV dose, MMD, skin type, and pre-exposure pigmentation was significant after one exposure.
  • After five exposures, this correlation remained significant only for narrowband UVB and Solar Simulator; UVA and UVA1 MMD were independent of pre-exposure pigmentation.
  • Pre-exposure pigmentation was a stronger predictor of MMD than skin type.
  • MMD was independent of pre-exposure pigmentation for UVA and UVA1, indicating similar SEDs for fair and dark skin.
  • Shorter wavelengths (UVB) were less melanogenic than longer wavelengths (UVA1).

Conclusions:

  • MMD after multiple UV exposures is influenced by UV source and pre-exposure pigmentation.
  • UVA1 is the most melanogenic UV source, with MMD independent of skin pigmentation.
  • Pre-exposure pigmentation is a more reliable predictor of MMD than skin type, particularly for UVA exposure.
  • UVB sources require higher doses for MMD in more pigmented skin.
  • Findings suggest that the number of Standard Erythema Doses (SEDs) to achieve MMD can be similar for fair and dark skin types with UVA exposure.