The common cold, a sinus infection, old age and nasal polyps can cause loss of smell, or anosmia, Mayo Clinic reports. Other causes include Kallmann syndrome, bony deformity inside the nose and exposure to toxic chemicals, such as solvents and pesticides. The condition can be partial, complete, temporary or permanent depending upon the underlying cause. Anosmia can cause loss of appetite, eventually leading to weight loss, depression and malnutrition.
Common colds and sinus infections can irritate or damage mucous membrane lining in the nose, leading to loss of smell, explains Mayo Clinic. The condition can cause temporary or irreversible destruction of the membranes. Nasal polyps and bony malformation in the nose may cause nasal obstruction, interfering with the flow of air.
Aging and exposure to poisonous chemicals may damage the oflactory system, which contains nerves that convey sensory information to the brain, according to Mayo Clinic. Damage to the system causes anosmia. People who are at least 60 years old are likely to experience irreversible loss of smell. Kallmann syndrome, a condition in which testicles are unable to produce sperms, and brain surgery can also destroy receptors in the oflactory pathway, causing the problem.
A patient with a cold or a sinus infection should contact a doctor if he experiences persistent loss of smell, advises Mayo Clinic. Prescription antibiotics may help clear nasal blockages and counter bacterial infection.