Ever since my fiancé had the swine flu, he has not been able to smell or taste anything. What might have caused this?
Probably the most common cause would be the development of a sinus infection. When the nasal passages and sinuses become swollen and filled with mucus from a cold or flu, the condition sometimes lingers after the illness, causing pain or pressure in the cheeks or forehead, postnasal drip, loss of the sense of smell, and fatigue. Our ability to taste is reliant on our ability to smell, so the two senses are often affected together. If this seems as if it might be the cause, then your fiancé should see his primary care provider if the symptoms do not improve gradually over the span of a couple of weeks. Most sinus infections clear up without treatment within that time.
A second cause could be the viral infection itself. We have delicate nerve endings in the linings of our nasal passages that can be damaged by some respiratory viruses, even in the absence of a sinus infection. The nerve endings recover in most cases, although it can take a considerable amount of time.
A third explanation might be the use of over-the-counter nasal sprays that contain zinc (such as Zicam), which occasionally cause loss of the sense of smell. These sprays are marketed for treatment of common colds, but please make sure your fiancé is not using a product like this. If he is, he should stop immediately.