EVALUATION OF SEVERAL VARIATIONS OF THE MOUSE EAR SWELLING TEST (MEST) FOR DETECTION OF WEAK AND MODERATE CONTACT SENSITIZERS

The ability of a chemical to cause contact sensitization has tradition ally been evaluated in animal models typically using the guinea pig. H owever, these methods are expensive and require subjective analysis of erythema, which makes evaluation of dyes difficult. The mouse ear swe lling test (MEST) is a more quantitative and less costly method, but i t has not always been reliable for the detection of moderate and weak sensitizers. To identify a MEST that can reliably detect weak sensitiz ers, several published MEST procedures were examined using the strong sensitizer 2,4-dinitrofluorobenzene (DNFB) and three weaker sensitizer s, glutaraldehyde, formalin, and an azo dye (Solvent Red 1 [SR 1 ]). A lmost all variations of the MEST procedures detected the strong sensit izer (DNFB) after optimizing the chemical concentration and sensitizin g procedure; however, only one protocol detected the weaker sensitizer s, glutaraldehyde, formalin, and SR1. This sensitive MEST protocol req uired test animals to be fed a vitamin A-supplemented diet for 4 weeks prior to sensitization. We concluded that the use of a vitamin A diet with the MEST proved to be the best procedure to enhance the sensitiv ity and detection of weak sensitizers.