First, scent molecules are complex. They bind to multiple olfactory receptors with differing affinity, ie. there is no "Vanilla" receptor, or "Rose" receptor, but the combination of binding to multiple receptors causes a cascade of electrical signals to go to the brain where it is 'interpreted' There are about 900 olfactory related genes identified in humans, dogs and other canines have many more and can detect smells 10,000 weaker than humans! I don't know much about some people not being able to smell certain things, but I do know it is scientifically proven that certain scents are "invisible" to certain people. Couple that with things like smoking, or living in a polluted environment full of other smells, and something as subtle but pervasive as Iso E Super may go undetected. It is in fact very strong in "whiffs and waves" to me, even at light application, but it dances and hides, coming out at unexpected times. It smells like pepper and sort of like Black Tourmaline's "ground stone" smell to me.