Taste disturbance

Taste impairments/disturbance (dysgeusia) are alterations of this normal gustatory functioning that may result in either:

• complete taste losses (ageusia)
• partial reductions (hypogeusia)
• over-acuteness of the sense of taste (hypergeusia)

Taste disturbances are not life-threatening conditions, but they can cause sufficient discomfort and lead to appetite loss and changes in eating habits, with possible effects on health.

Causes of a taste disturbance to consider include:

• upper respiratory tract infection - the taste of food is dependent on the smell
• anosmia
• glossopharyngeal nerve palsy - loss of taste on the posterior third of the tongue
• facial nerve palsy
• chronic adrenal insufficiency - increased sensitivity to the taste of salt, sucrose, urea and other substances

A much more detailed list of causes (1,2,3):

Common causes include:

• nasal and sinus disease (e.g., allergic or vasomotor rhinitis, chronic sinusitis, nasal polyps, adenoid hypertrophy)
• upper respiratory infection
• head trauma (e.g., frontal skull fracture, occipital injury, nasal fracture)
• cigarette smoking
• neurodegenerative disease (e.g., Alzheimer's disease, Parkinson's disease, multiple sclerosis)
• increasing age
• disturbances or loss of smell and taste are predominant neurological symptoms of infection by recent Coronavirus disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus strain 2 (SARS-CoV-2), as well as by previous both endemic and pandemic coronaviruses such as Middle East Respiratory Syndrome Coronavirus (MERS-CoV) and SARS-CoV (4)

Less common causes include

• drug induced - see linked item
• cocaine abuse (intranasal)
• toxic chemical exposure (e.g., benzene, benzol, butyl acetate, carbon disulfide, chlorine, ethyl acetate, formaldehyde, hydrogen selenide, paint solvents, sulfuric acid, thrichloroethylene)
• industrial agent exposure (e.g., ashes, cadmium, chalk, chromium, iron carboxyl, lead, nickel, silicone dioxide)
• nutritional factors (e.g., vitamin deficiency [A, B6, B12], trace metal deficiency [zinc, copper], malnutrition, chronic renal failure, liver disease [including cirrhosis], cancer, acquired immunodeficiency syndrome)
• glossopharyngeal nerve palsy - loss of taste on the posterior third of the tongue
• facial nerve palsy
• radiation treatment of head and neck
• congenital conditions (e.g., congenital anosmia, Kallmann's syndrome)

Uncommon causes include:

• neoplasm or brain tumor (e.g., osteoma, olfactory groove or cribiform plate meningioma, frontal lobe tumor, temporal lobe tumor, pituitary tumor, aneurysm, esthesioneuroblastoma, melanoma, squamous cell carcinoma)
• psychiatric conditions (e.g.schizophrenia, depression, olfactory reference syndrome)
• endocrine disorders (e.g., adrenocortical insufficiency, Cushing's syndrome, diabetes mellitus, hypothyroidism, primary amenorrhea, pseudohypoparathyroidism, Kallmann's syndrome, Turner's syndrome)
• pregnancy
• epilepsy (olfactory aura)
• migraine headache (olfactory aura)
• cerebrovascular accident
• Sjögren's syndrome
• Systemic lupus erythematosus

Reference:

1. Bromley SM. Smell and Taste Disorders: A Primary Care Approach.Am Fam Physician. 2000 Jan 15;61(2):427-436.
2. Prescriber 1999; 10 (12): 94.
3. Pulse 2004; 63 (47): 80.
4. Risso D, Drayna D, Morini G. Alteration, Reduction and Taste Loss: Main Causes and Potential Implications on Dietary Habits. Nutrients. 2020 Oct 27;12(11):3284.