I once did a flush with Olive-Oil that had become somewhat rancid. I really didn't notice until I had swallowed more than half the drink. I went ahead and finished the vile tasting concoction, but felt very nauseous and constanly burped the fowl taste all night. In the morning though, I had a successful flush. Still that experience really turned me off the taste and smell of olive oil. I used to use it all the time, but now can barely stand it for flushing. And-I do make sure its fresh.