What is olfactory loss?

Olfactory loss refers to the decrease or complete loss of the sense of smell. It can occur due to various causes, including neurodegenerative diseases like Parkinson's and Alzheimer's. In fact, losing one's sense of smell is often one of the earliest signs of such diseases. The loss is nonspecific, meaning it's not exclusively linked to any single condition and could be due to many different reasons. The olfactory system, where smell is processed, is highlighted as a potential route for the onset of neurodegenerative diseases, with theories suggesting that pathogens could enter the brain through the olfactory system and cause Alzheimer's disease 1.