A new protocol and criteria for quantitative determination of sensitization potencies of chemicals by guinea pig maximization test.

This paper presents precise sensitization test data of 15 chemicals with a wide spectrum of sensitization potencies, and proposes a new protocol and criteria for quantitative evaluation of sensitization potencies of chemicals. The tests were performed according to the design of Magnusson and Kligman, changing the application concentrations for induction as well as for challenge phases. 3-dimensional relationships between mean response (or sensitization rate), induction and challenge concentrations were found in all chemicals tested. The following 2 values are proposed as a quantitative measure of sensitization potency: (a) the minimum induction concentration that induces a positive response; (b) the challenge concentration that induces a mean response approximately equal to 1.0 among the animals applied with the highest concentration for induction. Both values coincided with each other within the range of 1 order of magnitude in every compound except 2. The values varied by 5 orders or more of magnitude among the compounds, showing a wide variation of sensitization potencies among chemicals. A good correlation was found for every chemical between the value of sensitization potency thus obtained and the residual levels in causative products in human cases of allergic contact dermatitis. A new experimental protocol for obtaining values (a) and (b) is proposed.