Anosmia is a condition, where either by birth or by accident we lose the ability to smell. Temporary anosmia (anosmic, adj.) can also be automatically induced by continued exposure to a certain smell. For example this is the reason why we often stop smelling the fragrance we are wearing on ourselves, when others can still perceive it. Temporary anosmia is actually a primitive biological survival mechanism, allowing us to tune out of sensory cues in the existing environment to ensure we can immediately recognise new olfactory cues that may be introduced (think dangerous animals for example).
More recently interest in the condition of anosmia has increased due to the effects (sometimes long lasting) of the COVID-19 virus on the human ability to smell.
Some researchers have focused on programmes to re-train the nose (and indeed the brain) on how to smell.