Sunburn protection by longwave ultraviolet radiation-induced pigmentation

Area of Science:

• Dermatology
• Photobiology
• Skin Physiology

Background:

• Melanin pigment is known to play a role in skin's natural defense against ultraviolet radiation.
• The specific contribution of UV-A induced melanogenesis to sunburn protection requires further elucidation.

Purpose of the Study:

• To investigate the protective role of melanin pigment, stimulated by ultraviolet-A (UV-A) radiation, against sunburn.
• To quantify the sunburn protection offered by UV-A induced tanning.

Main Methods:

• Deep tans were induced in volunteers via repeated exposure to UV-A radiation.
• Minimal erythema dose (MED) was determined for both tanned and untanned skin.
• Transmission studies were conducted on isolated stratum corneum sheets from tanned and untanned skin.

Main Results:

• UV-A tanning stimulated melanogenesis without significant stratum corneum thickening.
• Tanned skin required 2-3 times the MED to induce redness compared to untanned skin.
• Isolated stratum corneum from tanned skin filtered approximately twice as much UV radiation compared to untanned skin.

Conclusions:

• UV-A induced tanning enhances the filtering capacity of the skin's stratum corneum.
• While UV-A tanning offers a degree of protection, it does not confer substantial resistance to sunburn.