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Updated: Dec 15, 2025

Precision Implementation of Minimal Erythema Dose MED Testing to Assess Individual Variation in Human Inflammatory Response
Published on: October 3, 2019
Global data of unprotected skin minimal erythema dose relationship to Individual Typology Angle
1Sun & Skin Consulting, New Holland, PA, USA.
Background:
Determination of the Minimal Erythema Dose (MEDu ) of unprotected skin is perhaps the most critical aspect of the Sun Protection Factor (SPF) value and disproportionately influences the SPF. Individual Typology Angle (ITA°), a skin reflectance measure of the skin's pigmentation, has been used by many clinical laboratories to estimate the MEDu values for SPF testing.
Methods:
Individual Typology Angle and unprotected MEDu data on 9931 individuals were received from 12 laboratories located on 5 continents to determine MEDu values in prospective sunscreen testing studies.
Results:
These data were compiled and normalized by laboratory (to account for differences in number of subjects within each laboratory). A polynomial regression best fits the relationship between ITA° and their MEDu and may be used to accurately predict the MEDu of an unknown test subject.
Conclusion:
The regression data have been incorporated into the latest ISO24444 (Cosmetics - Protection test methods - in vivo determination of the sun protection factor (SPF), 2019) in vivo Sunscreen testing method that must be utilized to determine a subject's provisional MEDu for the testing procedure. Use of this common ITA°-MEDu relationship will help to minimize SPF variability between testing laboratories due to use of widely varying MEDu values.
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