The guinea pig maximization test (GPMT) (27,30) combines FCA, irritancy, intradermal injection, and occlusive topical application during the induction period. Two identical sets of 0.1-mL intradermal injections of 50/50 FCA/water, test material in water, paraffin oil, or propylene glycol and the same dose of test material in FCA/vehicle are placed on a filter paper, placed over the shaved injection site, covered with approximately 4 X 8 cm occlusive surgical tape, and secured in place. If the test material is nonirritating, the test site is pretreated with 10% sodium lauryl sulfate (SLS) in petrolatum on day 6 to provoke an irritant reaction. After 48 h, test and control (vehicle alone) animals are challenged on the shaved flank with the highest nonirritating concentration and with the vehicle. Solutions are applied to filter paper secured in place and patches removed 24 h later. Reactions are visually evaluated 24 and 48 h after patch removal. Reactions are considered positive when they are more intense than the response to vehicle and the responses to the test materials in controls. The test material is rated as a weak-to-extreme sensitizer, based on the incidence of positives in the test group (Table 2).
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