Ageusia is the medical term for absence of taste, and it often results from a decreased sense of smell as the taste and smell sensations are closely related, according to MedicineNet. It also occurs as a side effect of certain medications and as part of the normal aging process.
In many cases, people experience a loss of taste when they have a problem with their sense of smell, says the National Institute On Deafness and Other Communication Disorders (NIDCD). Chewing, drinking or digesting food releases tiny molecules that stimulate special sensory cells in the mouth and throat. This is how people are able to taste food. A special channel connecting the roof of the throat to the nose helps activate the sense of smell. When it gets blocked, for example when the nose gets clogged by a cold or flu, the food's odors fail to reach sensory cells in the nose, leading to a loss of sense of taste.
The NIDCD states that many people also develop taste problems after an illness or injury although some are born with taste disorders. Some of the causes of taste disorders include head injuries, surgeries to the ear nose or throat, upper respiratory and middle ear infections, radiation therapy for head and neck cancers, poor oral hygiene, and dental problems.