Influence of Physiological Parameters on the Production of Protoporphyrin IX in Human Skin by Topical Application of 5-Aminolevulinic Acid and its Hexylester

Formation of protoporphyrin IX (PpIX) after topical application of 5-aminolevulinic acid (ALA) and its hexylester derivative (ALA-Hex) was studied on healthy human skin. Temperature, density of hair follicles, epidermal and skin thickness were measured on the application sites. The skin temperature was found to be the strongest determinant for PpIX formation. The PpIX fluorescence increase was about 25% per degree Celsius. Formation of PpIX was found to be independent of the density of hair follicles. A weak correlation was found between the PpIX fluorescence and the thickness of epidermis and skin. Sun exposure seems to reduce the production of PpIX slightly.