title: Pigmentation after single and multiple UV-exposures depending on UV-spectrum.
abstract: Minimal pigmentation dose (MMD) after a single UV-exposure is well investigated. Whereas only few studies have established MMD after multiple UV-exposures and mainly in fair-skinned persons. The purpose of this study was to establish MMD 1 week after, respectively, one and five UV-exposures in volunteers with a large variation in constitutive pigmentation. A total of 52 volunteers (skin Types II-V) had skin pigmentation quantified by reflectance spectroscopy. They were UV-exposed on the back for 1 and 5 days using a Solar Simulator, narrowband UVB, broadband UVA and UVA1. For all sources a higher dose was needed the more pigmented the skin, except for UVA1. After one UV-exposure, we found a significant positive linear correlation between UV-dose to one MMD, skin type and pre-exposure skin pigmentation. After five UV-exposures the positive linear correlation between UV-dose and MMD and skin type was only significant for narrow band UVB, pre-exposure skin pigmentation was significant also for Solar Simulator. For UVA and particularly UVA1 the MMD was independent of pre-exposure pigmentation. The number of SED to MMD is therefore almost the same for very fair-skinned and dark-skinned persons. Pre-exposure pigmentation was clearly more predictive of MMD than skin type. 50% of MMD equals a pigmentation increase of 1%. The shorter the wavelengths the higher the SED to produce MMD. Solar was the least melanogenic and UVA1 the most melanogenic. For the UVB-sources a higher dose was needed the more pigmented the skin. For UVA the MMD was independent of pre-exposure pigmentation.
authors.affiliation: Department of Dermatology, D92, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark. mette@ravnbak.dk
authors.forename: M H
authors.initials: MH
authors.lastname: Ravnbak
authors.forename: H C
authors.initials: HC
authors.lastname: Wulf
mesh_terms: D000328:Adult; D044466:Asian People; D004307:Dose-Response Relationship, Radiation; D004890:Erythema / Q000209:etiology; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D008297:Male; D008543:Melanins / Q000378:metabolism; D012867:Skin / Q000378:metabolism / Q000528:radiation effects; D012880:Skin Pigmentation / Q000235:genetics / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects / Q000145:classification*; D044465:White People
chemical_list: D008543:Melanins