Scratching behavior contributes to the ear swelling of CH. Collars were used during the sensitization and/or elicitation of CH to prevent mice from scratching the ears (A). Ear swelling of CH significantly decreased when collars were used during the elicitation phase (B). Applying the collars during the last 12 h, of the 24 h after elicitation significantly inhibited ear swelling(C). The longer the collars were used in the elicitation phase the greater the suppression of CH (D). S: sensitization, E: elicitation, S/E: both sensitization and elicitation, h: hour(s), C: use of collars, SD: standard deviation. Note that some description of statistical analysis, such as those between vehicle-treated group and sensitized group, were omitted in graph 2B for clarity. **p < 0.01, *p < 0.05.