Dysgeusia is a broad term to describe any disturbance of the sense of taste. This may include :
- Ageusia : total loss of taste
- Hypogeusia : diminished taste sensitivity
- Parageusia : taste with no stimuli present
- Cacogeusia : foul taste sensations (causes discussed under Bad Taste in Mouth) is a type of parageusia.
Disruption of the sense of taste is not isolated to the function of the taste buds and taste centers in the brain. The sense of smell, temperature and tactile sensation on the tongue may also influence the sense of taste. One of the common causes of dysgeusia is due to diminished smell (hyposmia) or even a loss of sense of the smell (anosmia).
While local factors in the mouth, nose and throat account for most of the causes of dysgeusia, problems with the nerve pathways and even brain centers may also be responsible for the diminished, distorted or total loss of the taste sensation.
Causes of Dysgeusia
Trauma, mechanical or chemical, to the taste buds, nerves or taste centers in the brain or related areas of the alimentary and respiratory tract may be responsible for a distortion in the sense of taste. This may be due to :
- Chemicals – medication and substances mentioned below, poisons, strong acids (including stomach acid in GERD), caustic agents
- Surgery – damage to cranial nerves or branches : facial nerve (CN VII), glossopharyngeal nerve (CN IX), hypoglossal nerve (CN XII)
- Hemorrhage (mouth, nose, esophagus) – metallic taste in the mouth
- Head trauma
Dysgeusia may occur in some patients with the following neurological disorders.
- Parkinson’s disease
- Multiple sclerosis
Infections can disrupt the functioning of the taste buds and lead to a variety of disturbances, including ageusia and hypogeusia. Infections, especially if there is pus or blood in the mouth, may lead to a bad taste in the mouth or a metallic taste (cacogeusia, parageusia). The infections may occur in the following areas :
- Mouth – tongue, cheek, gums
- Upper respiratory tract – nose, throat and larynx
- Ear – particularly middle ear infections
- Dental – tooth cavity, gingivitis, dental abscess
- Systemic – HIV
Medication, Substances and Treatment
- Drugs – certain antibiotics, antihistamines, CNS depressants / stimulants used in the treatment of various psychiatric disorders and insomnia.
- Alcohol abuse
- Narcotics (most)
- Cigarette smoking
- Nicotine replacement products
- Radiation therapy
- Diabetes mellitus (diabetic neuropathy)
- Zinc deficiency
- Vitamin B12 deficiency
- Sjogren’s syndrome
- Kidney failure