Related Experiment Video
Updated: Aug 26, 2026

Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
Published on: September 7, 2013
The effects of ultraviolet exposure on skin melanin pigmentation
1Department of Dermatology, Pasteur Hospital, Nice, France.
Abstract:
The main clinical, histological, ultrastructural and biochemical changes to the pigmentary system following photo-exposure are reviewed. Acute exposure to ultraviolet (UV) radiation induces an immediate pigment-darkening reaction, due to photo-oxidation of preformed melanin, followed by delayed tanning, the mechanism of which is unknown. Chronic exposure to UV induces photo-ageing with uneven pigment distribution. The most common pigmented lesions on chronically sun-exposed skin include ephelides, solar lentigines and pigmented solar keratoses. Idiopathic guttate hypomelanosis is also common in sun-exposed skin and may be considered as a manifestation of photo-ageing. Chronic UV also appears to induce cutaneous melanomas. Psolaren UVA lentigines and sunbed lentigines provide good arguments for the fact that UV exposure can induce melanocyte dysplasia. In addition, various tumours involving the keratinocyte population are associated with increased pigmentation, suggesting a concomitant alteration in melanocyte function, as in the case of pigmented epitheliomas and pigmented actinic keratoses. The exact nature of the interactions between photo-exposure and melanocytes has yet to be fully established.
Related Concept Videos
Mutations
Mutations
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Role of Skin in Vitamin D Synthesis
The solar UV B rays (290-315 nm) are absorbed by the skin, and 7-dehydrocholesterol (provitamin D3) photolyzes it to previtamin D3, which undergoes a rapid transformation to vitamin D3(cholecalciferol).
Pigmentation
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 Perspectives
Albinism
Albinism is a genetic disorder that affects (completely or partially) the coloring of skin, hair, and eyes. The defect is primarily...
Skin Cancer
Basal Cell Carcinoma (BCC): BCC is the most common type of skin cancer, accounting for about 80% of cases. It typically develops in...

