Head injuries, especially in young adults. Viral infections. Alzheimer’s disease, predominantly in the elderly.
Head injuries often cause permanent loss of smell, as in traffic accidents. These injuries can destroy or sever the olfactory nerve fibers, which transmit signals from the olfactory receptors to the brain. Infections or tumors near the cribriform plate of the nasal cavity, which separates the nasal and brain cavities, can also affect the olfactory nerves.
Respiratory tract infections, particularly influenza
They are another popular cause, possibly responsible for up to a quarter of cases of decreased sense of smell. Degenerative brain diseases, such as Alzheimer’s, can destroy the olfactory nerves, resulting in loss of smell.
Less common reasons include medications, tumors, nasal infections, allergies, sinus infections, and radiation therapy for can.cer, which can temporarily or permanently affect smell or taste.
In extremely rare cases, anosmia can be congenital.
Anosmia, or reduced olfactory sensitivity, may serve as an early indicator of COVID-19, a severe acute respiratory illness caused by the SARS-CoV-2 coronavirus.
Evaluating smell loss involves observing war:ning signs, particularly when resulted by head injuries, nervous system symptoms, or sudden onset of signals that indicate immediate medical evaluation.
