I think i may be coming slightly allergic to ingested levomenthol, I've always been allergic to it externally Deep heat for instance causes a intense rash in areas unsprayed. I've got a pretty bad cough and i've been taking benylin.. Shortly after taking I begin to feel nauseous. So i didn't use it for a day and the nausea vanished I cant really find out any-thing about levomenthol side effects on the net..