I don't have a very good answer for you as it all depends on how your body is reacting to this "invader" (urusiol oil) and how well you tend to the rash. We all react differently. Generally, the rash lasts about 2 weeks with the most itch from about day 1 to day 8. Yours may last only a few days or it may go a full 2 weeks or so. The blisters are open sores and you should treat it as such. Make sure that the rash area stays clean and dry and generally uncovered as this will help the healing process.

To show you how the rash varies from person to person, for me the rash tends to fade away in about 5 or 6 days but for my husband he gets the full 2 week treatment.

Good luck and keep that rash dry.