There are, speaking of forensics, creams available to rub on the upper lip. These might not strictly disable your sense of smell, but will overpower any other odors for a while. Violets have the ability to block the sense of smell, but it will fade fairly rapidly, then the violet smell returns, spontaneously. read more
One of the primary reasons is the fact that it is closely associated to your sense of taste. If you have any doubt about that, try to taste something while you pinch your nose. Most of all, having a good sense of smell increases your enjoyment of life. read more