Skin Exposure to UV and Erythemal Dosage

The inflammatory response of the skin to UV irradiation causes vasodilation of cutaneous blood vessels, resulting in reddening of the skin, or erythema. The efficiency of UV wavelengths to induce erythema is described by the CIE erythemal action spectrum, published in CIE S 007/E-1998 (ISO 17166:1999).

CIE Erythemal Action Curve

This action spectrum forms the basis of the minimum erythemal dose, the standard erythemal dose unit, and the UV index used for public information on exposure to solar UV.

Erythemal Dose

The complex range of interactions between UV light and tissue are highly photochemical in nature, after the Bunson-Roscoe law of reciprocity which states that the biological response is proportional to dose and not on the profile of exposure.

The skin can be exposed to light from the entire hemisphere over its surface and therefore, spectral irradiance is the measurement quantity to consider. Erythemal irradiance is calculated from integration of the erythema action curve and the product of spectral irradiance.  The standard erythemal dose is 100 J.m-2 erythemal irradiance.

The minimum erythemal dose, to induce just-detectable erythema can be established by exposing the skin to a variety of erythemal doses followed by assessment of the exposure sites, or estimated based on the type of the skin.

Type Description MED (SED)
I Fair skinned Caucasians who burn very easily and never tan 2
II Fair skinned Caucasians who burn easily and tan slowly and with difficulty 2.5
III Medium skinned Caucasians who burn rarely and tan relatively easily 3
IV Darker skinned Caucasians who virtually never burn and tan readily, e.g. some individuals with Mediterranean ancestry 4.5
V Asian or Indian skin 6
VI Afro-Caribbean or Black skin 10


Bentham Instruments Limited.

This information has been sourced, reviewed and adapted from materials provided by Bentham Instruments Limited.

For more information on this source, please visit Bentham Instruments Limited.


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