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Related Concept Videos

Pigmentation01:19

Pigmentation

The color of the skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. The melanin is transferred to the keratinocytes via melanosomes.
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...
Changes in Skin Color: Clinical Perspectives01:14

Changes in Skin Color: Clinical Perspectives

The first thing a clinician sees is the skin, so the examination of the skin should be part of any thorough physical examination. Most skin disorders are relatively benign, but a few, including melanomas, can be fatal if untreated. A couple of the more noticeable disorders, albinism and vitiligo, affect the appearance of the skin and its accessory organs.
Albinism
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Skin Cancer01:30

Skin Cancer

Skin cancer is a type of cancer that occurs when there is an abnormal growth of skin cells, usually triggered by damage to the DNA within the skin cells. It is primarily caused by exposure to ultraviolet (UV) radiation from the sun or artificial sources like tanning beds. Skin cancer is the most common type of cancer worldwide, and its incidence continues to rise.
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Role of Skin in Vitamin D Synthesis01:23

Role of Skin in Vitamin D Synthesis

The skin plays a crucial role in the synthesis of vitamin D, a vital nutrient for various physiological processes in the body. Vitamin D is unique because it can be synthesized in the skin through a series of chemical reactions triggered by exposure to ultraviolet B (UVB) radiation from sunlight.
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Photoreceptors and Visual Pathways01:22

Photoreceptors and Visual Pathways

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Related Experiment Video

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Studying Chronic Exposure of Mice to Ultraviolet B Radiation
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Published on: August 19, 2025

Skin pigmentation kinetics after UVB exposure.

Mette H Ravnbak1, Peter A Philipsen, Stine R Wiegell

  • 1Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Denmark. mette@ravnbak.dk

Acta Dermato-Venereologica
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Summary

This study shows that darker skin requires higher ultraviolet B (UVB) doses for minimal pigmentation, but repeated exposures reduce the necessary dose, lowering sunburn risk. Pigmentation fading occurred over months, irrespective of skin type or UV exposure frequency.

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Area of Science:

  • Dermatology
  • Photobiology
  • Human Physiology

Background:

  • Limited research exists on pigmentation kinetics after ultraviolet B (UVB) exposure, particularly in diverse skin types.
  • Previous studies focused solely on fair-skinned individuals, leaving a gap in understanding tanning responses across different ethnicities.

Purpose of the Study:

  • To investigate the kinetics of skin pigmentation increase to steady state and subsequent fading after UVB exposure in both fair-skinned (Scandinavians) and darker-skinned (Indians/Pakistanis) individuals.
  • To compare the UV doses required for minimal pigmentation and assess the impact of repeated exposures on these doses and sunburn risk across different ethnic groups.

Main Methods:

  • 12 Scandinavians and 12 Indians/Pakistanis were exposed to a Solar Simulator and narrowband UVB.
  • UV irradiation was administered 6 times on the right back and 12 times on the left back over 3 weeks, using individually predetermined sub-Minimal Melanogenesis Doses.
  • Skin pigmentation was quantified using skin remittance measurements at 555 nm and 660 nm to correct for erythema.

Main Results:

  • Absolute pigmentation increase was independent of pre-exposure levels, resulting in a higher percentage increase in fair-skinned individuals.
  • Darker-skinned individuals required a higher UV dose for minimal pigmentation across single and multiple exposures for both UV sources.
  • Repeated UVB exposures (6 and 12) reduced the dose needed for minimal pigmentation by factors of 2 and 3, respectively, decreasing sunburn risk but increasing cumulative dose.

Conclusions:

  • The UV dose required for minimal pigmentation is higher in darker skin types, but repeated exposures enhance tanning efficiency and reduce sunburn risk.
  • Pigmentation fading occurred over 4-5 months and was not influenced by the frequency of UV exposure or ethnic origin.
  • These findings provide crucial insights into tanning kinetics and photoprotection strategies across diverse skin types.