This will be a single-blinded, vehicle-controlled randomized study in healthy controls to test the efficacy of the topical gel formulation with three differing concentrations of acetaminophen (APAP) for itch relief. To detect medium effects of the treatments with a given α of 0.5 and an error probability of 0.05, with a power of 0.95, the number of participants needed is 36 (10 within post hoc pairwise comparisons).
