OIfactory fatigue (like wearout or sensitivity loss) is a name for the common experience of losing sensitivity to odors afler continued smelling. It occurs when we are exposed with each breath to a relatively unvarying source of odor. Our olfactory system is robust—but if it is faced with a continuous stream of constant odorant (perfume, flavor, or noxious environmental odor), we lose our sensitivity. We adapt to the stream of odor, and it seems weaker. In its most dramatic form, olfactory adaptation produces a total loss of odor perception.
Adaptation characterizes all senses to greater or lesser degrees. Each sense is susceptible to adaptation to a continuous stream of unvarying sensory inputs. As we emerge from a darkened movie theater to daylight, we find that the outside is too bright. It takes a few moments to re-adapt to the outside. In olfaction, fortunately, adaptation is a temporary phenomenon, soon dissipated by breathing nonodorized air.
Olfactory self adaptation
If we smell a substance, and shortly thereafter smell the same substance at a lower concentration, the odor sensation may either be absent (total adaptation) or considerably weakened. “Self adaptation” refers to this weakening of olfactory intensity.