Common causes

Oral and perioral infections (e.g., candidiasis, gingivitis, herpes simplex, periodontitis, sialadenitis)

Bell's palsy

Medications (see Table 2)

Oral appliances (e.g., dentures, filling materials, tooth prosthetics)

Dental procedures (e.g., tooth extraction, root canal)

Age

Less common causes

Nutritional factors (e.g., vitamin deficiency [B3, B12], trace metal deficiency [zinc, copper], malnutrition, chronic renal failure, liver disease [including cirrhosis], cancer, acquired immunodeficiency syndrome)

Tumor or lesions associated with taste pathways (e.g., oral cavity cancer, neoplasm of skull base)

Head trauma

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., chromium, lead, copper)

Radiation treatment of head and neck

Uncommon causes

Psychiatric conditions (e.g., depression, anorexia nervosa, bulimia)

Epilepsy (gustatory aura)

Migraine headache (gustatory aura)

Sjögren's syndrome

Multiple sclerosis

Endocrine disorders (e.g., adrenocortical insufficiency, Cushing's syndrome, diabetes mellitus, hypothyroidism, panhypopituitarism, pseudohypoparathyroidism, Kallmann's syndrome, Turner's syndrome)