Modified Draize test: it differs from the original Draize test by subjecting the volunteers to a continuous induction period with patch exchange 3 times a week until a total of 10 patches have been applied. The patches are reapplied to the same site, and only if moderate inflammation has developed, the next patch is moved to an adjacent skin site. Challenge is
performed on naive skin two weeks later with a 72-hour patch test with a non-irritating concentration of the substance.