The mouse ear swelling test (MEST) in the 1990s.

The mouse ear swelling test (MEST) was developed in the early 1980s to provide a lower cost, shorter and objectively graded alternative to the existing guinea pig based tests for delayed contact hypersensitivity. In the ensuing time, the test design has been modified and its use has been extended to additional applications (phototoxicity and photosensitisation screening and as a mechanistic tool in studying tumor promoting agents) and to evaluating a broader range of test materials (treated fabrics, medical devices, environmental pollutants, specialty chemicals, drugs, etc.) in the hands of new investigators. Likewise, other murine based tests have been developed. The MEST and one other murine test (the local lymph node assay, or LLNA) have also now been included in the lists of regulatorily accepted sensitization test systems. The current version of the MEST protocol is presented here, along with the rationale for changes, a review of evaluations and interlaboratory trials and an overview of the range of uses to which it has been applied.