Olfactory disorders following upper respiratory tract infections.

Postviral olfactory disorders usually occur after an upper respiratory tract infection (URTI) associated with a common cold or influenza. With a prevalence between 11 and 40% they are among the common causes of olfactory disorders. Women are more often affected than men and post-URTI disorders usually occur between the fourth and eighth decade of life. The exact location of the damage in post-URTI is not yet known even though from biopsies a direct damage of the olfactory receptor cells is very likely. Nevertheless, central mechanisms cannot completely be ruled out. The diagnosis is made according to the history, clinical examination and olfactory testing. Affected patients usually recall the acute URTI and a close temporal connection should be present to establish the diagnosis. Spontaneous recovery might occur within 2 years. So far, no effective therapy exists even though specific olfactory training might be promising.