[Specific anosmia as a principle of olfactory perception]

Specific anosmia, the inability to perceive a specific odor, while olfactory perception is otherwise intact, is known as a rather seldom phenomenon. By testing the prevalence of specific anosmia to 20 different odors in a sample of 1600 people, we were able to estimate the general prevalence of anosmia. This revealed that specific anosmia is not rare at all. In contrast, the general likelihood for specific anosmia approaches 1. In addition, specific anosmia can be very well reversed by "smell training" during the course of 3 months. To summarize, specific anosmia seems to be a rule, not an exception, of olfactory sensation. The lack of perception of certain odors may constitute a flexible peripheral filter mechanism, which can be adapted by exposure to odors.