Anosmia is more commonly known as simply a loss of smell. The severity can range from partial to complete and from temporary to permanent.
Anosmia is usually caused by an irritation in the lining of your nose or an obstruction in your nasal passage. Many things can cause the lining of your nose to become irritated: a common cold, a sinus infection, hay fever or the flu. A nasal polyp, tumor or a deformity inside the nose can all cause an obstruction.
While much less common, damage to the part of the brain that is responsible for your sense of smell can also cause anosmia. This damage can be caused by normal aging, a traumatic brain injury and a number of disorders and syndromes that affect the brain.
Typically, your sense of smell will return on its own after a few days. If this does not happen, you should contact your doctor, as it may be a symptom of a more serious condition. An antibiotic may be needed to treat a bacterial infection irritating your nasal passages and surgery may be needed to remove the nasal obstruction.