Ageusia

Ageusia is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami (meaning "pleasant/savory taste"). It is sometimes confused with anosmia – a loss of the sense of smell. Because the tongue can only feel texture and differentiate between sweet, sour, bitter, salty, and umami, most of what we think of as the sense of taste actually comes from smell. Ageusia is a lot rarer than hypogeusia – a partial loss of taste – and dysgeusia – a distortion or change of taste.
Causes.
The main causes of taste disorders are head trauma, infections of upper respiratory tract , exposure to toxic substances, causes relating to illness caused by medical examination or treatment, medicines, glossodynia ("burning mouth syndrome (BMS)") and COVID-19.
Diagnosis.
Aguesia is diagnosed by an otolaryngologist, who can look at a patient's loss of taste. To do this, a specialist will look into any other factors that could be causing the loss of taste, such as examining the head, nose, ears, and mouth. An otolaryngologist can also do of tests to assess the how bad the loss of taste is, which includes seeing specific tastes that a person can sense or recognize.