The effect of cosmetic vehicles on the penetration of N-nitrosodiethanolamine through excised human skin.

Cosmetic products are frequently applied to the skin by a large number of people, but some contain compounds that are potentially toxic, if absorption through the skin is sufficient. The percutaneous absorption of N-nitrosodiethanolamine (NDELA), an impurity in many cosmetic products, has been evaluated in diffusion cells using excised human skin. The nitrosamine was applied to the skin in vehicles with different solubility properties. The permeability constants for water (5.5 X 10(-6) cm hr-1) and propylene glycol (3.2 X 10(-6) cm hr-1) were small and similar. In isopropyl myristate, the permeability constant increased approximately 250-fold to 1.1 X 10(-3) cm hr-1. The NDELA membrane:vehicle partition coefficients were determined using trypsin-treated stratum corneum as the membrane. These coefficients were 1.8 and 1.0, respectively, for water and propylene glycol and 230 for isopropyl myristate. The permeability of NDELA through skin is apparently increased greatly when applied from sufficiently lipoidal formulations; this is primarily due to the favorable partition coefficients for NDELA from such formulations. The amount of NDELA penetrating the skin from 3 types of cosmetic products was calculated based on their different conditions of use. Products applied over large areas of the body that remain on the skin for long periods of time (i.e., sun tanning lotion) will result in the greatest absorption of NDELA if all other factors are equal.