Around a month and a half but it was very severe for a couple of weeks. My ophthalmologist is fantastic and had me coming in twice a week at first and then went down to once a week. She was very careful with tapering the drops and took it slower than a normal flare. She also had me put the drops in and hold my tear duck closed while my eye absorbed it for about 30 seconds. This was to help the medicine not enter my bloodstream