The suppression of the effector phase of CHS by R-848 is transient. Mice were sensitized with FITC. Six days later one group of mice was treated with R-848, and challenge was performed on the right ear in all groups. On day 7, R-848-treated animals were rechallenged on the left ear. Twenty-four hours after challenge or rechallenge, CHS was determined as increase in ear thickness relative to the vehicle-treated ear or to the thickness of the ear before challenge. Data represent means of 5 to 7 mice per group. Error bars indicate mean ± SD.