My son and I have been prescribed Tazorac 0.1% gel to use on EHK skin. I use it on my son's neck and on my hands. My doctor advised me to put it on for 15 minutes and then wash it off. It works okay but I'm curious to know if anyone leaves it on for longer and what the results are. I hate to think that I'm wasting this expensive ointment by washing it off before it has had a chance to work to it's potential. I have moderate EHK (thinkened palms and soles and ridged skin on flexor areas). Any information would be appreciated.