SHORT COMMUNICATION Circadiati rhythmicity of delayed hypersensitivity to oxazolone in the rat

Summary 1. A marked circadian rhythm was detected in the ear swelling of rats immunized and then challenged with oxazolone. 2. The peak response observed at 10.00 hours was over eight times the minimum at 16.00 hours. 3. As related tests are used frequently in man greater attention to clock time is necessary in clinical immunology.