Why do my taste buds change when I have a cold, sinus infection, allergy, flu ect.? Example - why does coke taste bad when I am sick? How does my nose change my taste?
Human taste buds allow us to perceive only four flavors: bitter, salty, sweet, and sour. Seventy to seventy-five percent of what we perceive as taste actually comes from our sense of smell--that is, the odor molecules from food that travel to the olfactory (smell related) receptor cells at the top of the nasal cavity give us most of our taste sensation. This is why conditions that affect one's sense of smell also appear to affect one's sense of taste (e.g., a common cold or bacterial sinus infection may produce such thick nasal mucus that, although your tongue can feel the texture and temperature of the food, the food odor molecules may not penetrate the mucus to reach the nasal olfactory receptor cells). Zicam zinc nasal gel use has resulted in actual lawsuits due to the side effect of zinc-induced prolonged or even permanent loss of both smell and taste (see the third paragraph in the second referenced website below about the components of the flavor of food). By the way, anosmia is the loss of the sense of smell, while ageusia is the loss of the sense of taste.
Smell and taste reference: http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/newton/tstesmll.html
Zicam smell and taste loss lawsuit: http://www.yourlawyer.com/topics/overview/Zicam