Sense of smell and taste is closely related, one can realize this by trying to taste onion while blocking the nose. Sometimes percieved taste in food is actually its smell, and if one is impaired the other is affected as well. Conditions like colds, presence of ongoing disease, fever and migraine tends to alter senses of smell and taste. Correcting the underlying condition can help regain smell and taste. Here are links: http://www.ask.com/wiki/Dysgeusiahttp://www.ask.com/wiki/ageusia
It is hard to tell when your sense of smell and taste will come back exactly, but if you’re undergoing certain treatment of taking up a particular medication, your sense of smell and taste may be back as soon as you are done with the treatment or your body becomes used to it. For some person, the sense comes back in a matter of week but for some, it even takes several months before it goes back to normal.
Sense of smell and taste are done by the tongue and nose respectively. They are interrelated and highly dependent on the nerves that surround them. Sense of smell and taste can be temporarily reduced or lost with illness like cold and fever, but you will have it back in a few days after getting well. If due to a permanent damage to the parts of the brain that interpret taste and smell, then you could lose the senses permanently too.