Ageusia

and Martina Feichter, medical editor and biologist Updated on

Dr. med. Fabian Sinowatz is a freelancer in the medical editorial team.

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Martina Feichter studied biology with an elective subject pharmacy in Innsbruck and also immersed herself in the world of medicinal plants. From there it was not far to other medical topics that still captivate her to this day. She trained as a journalist at the Axel Springer Academy in Hamburg and has been working for since 2007 - first as an editor and since 2012 as a freelance writer.

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Ageusia is when someone can practically no longer taste anything or at least no longer perceives certain flavors. Various causes come into consideration for this form of taste disturbance (taste disturbance). Find out here what these are, how to diagnose ageusia and what treatment options are available!

Ageusia: description

Doctors describe a loss of taste perception as ageusia. This extremely rare form of taste disturbance (dysgeusia) can be divided into three sub-forms:

• Complete ageusia: This means the complete loss of the ability to taste - so those affected can no longer taste anything at all.
• functional ageusia: the ability to taste is very clearly restricted here.
• partial ageusia: those affected can no longer perceive certain flavors (e.g. sweet).

Overall, taste disorders are less common than smell disorders. But they can be extremely uncomfortable and stressful for those affected. After all, a normal sense of taste is necessary in order to be able to enjoy food.

This is how taste is created

A sensory perception such as taste can only occur if the structures of the respective sensory system are intact. In the case of taste perception, basically three stations are necessary. A disturbance in one of these three stations can change the taste perception or even lead to a failure (ageusia):

• Taste Buds: They are the "sensory organ" for taste. A person has several thousand taste buds in the area of ​​the tongue and palate. They allow you to differentiate between five different flavors: sweet, sour, bitter, salty and umami (Japanese for savory and spicy).
• certain cranial nerves: of the total of twelve cranial nerves, three are responsible for taste (VII, X and IX). These three neural pathways carry information from the taste buds to the brain.
• Brain: The information that comes from the taste buds converges in the brain, is processed and only then perceived as a taste.

What other types of taste disorders are there?

Normal taste - called "normogeusia" - can be disturbed in various ways. Then one speaks of a taste disturbance or taste disturbance (dysgeusia). One form of this is the Augenusie. It is one of the quantitative taste disorders - just like hypergeusia and hypogeusia. There are also the qualitative taste disorders parageusia and phantogeusia:

Hypogeusia	reduced taste sensitivity compared to young, healthy test persons
Hypergeusia	oversensitive taste sensation compared to young, healthy test subjects
Parageusy	changed perception of taste sensations (e.g. sweet things can be perceived as bitter)
Phantogeusy	Perception of taste impressions without a source of irritation (e.g. inexplicable metallic taste in the mouth). Also called "taste hallucination".

Ageusia: causes and possible diseases

Ageusia can be epithelial, neural and / or central. That means: The taste perception of those affected is disturbed in at least one of the three stages of taste perception (taste buds in the oral mucosa - cranial nerves - brain). There are many possible causes for this. These include, for example:

• Infections such as flu (cold), flu, sinus infections (sinusitis), Covid-19 or oral mucosal infections with bacteria or fungi
• Nutrient deficiency, e.g. vitamin B12 deficiency, iron deficiency or zinc deficiency
• Sjogren's Syndrome and Other Causes of Dry Mouth
• psychiatric illnesses such as depression
• Diabetes (diabetes mellitus)
• Hypothyroidism
• Liver and kidney disease
• Inflammation of the brain (encephalitis) or cranial nerves (neuritis)
• Brain tumors
• traumatic brain injury
• epilepsy
• multiple sclerosis
• Diseases associated with the death of brain cells (neurodegenerative diseases), e.g. Alzheimer's
• Drugs, e.g.Antidepressants, chlorhexidine (for example as a mouth rinse for oral mucosa or gingivitis), terbinafine (anti-fungal agent), cytostatics (chemotherapy drugs)
• Radiation therapy in the head and neck area, e.g. for cancer of the larynx
• Operations, e.g. ear surgery or removal of the tonsils (tonsillectomy)
• Contact with toxic substances (including nicotine and alcohol)
• poor oral hygiene

Sometimes no cause for a taste disorder can be found either. It is then called idiopathic.

The most common causes of taste disorders in general include traumatic brain injuries, upper respiratory tract infections, exposure to toxic substances, medication and medical interventions (such as surgery or radiation therapy) and burning mouth syndrome (burning tongue).

Ageusia: When should you see a doctor?

If the taste sensation fails (ageusia) or is otherwise changed (hypogeusia, parageusia, etc.), this can be an indication of a previously undiscovered health disorder. Both harmless causes and dangerous diseases are possible as the cause of the taste disturbance.

So if you suspect you have a taste disorder, you should not hesitate, but go to your family doctor. He can use an exploratory examination to assess whether further clarification by specialists is necessary.

It is possible that ageusia (or another taste disorder) will go away "by itself" - for example, if the cause is a cold or the temporary use of a medication. In many other cases, however, spontaneous improvement is not to be expected. In addition, ageusia usually means an enormous loss of quality of life for those affected and in the worst case can even be a trigger for psychological problems such as depression. Therefore, you should always have a doctor clarify the loss of taste.

Ageusia: what does the doctor do?

The first point of contact for a taste disorder (such as ageusia) is the family doctor. He can already make an initial assessment by collecting the medical history in a detailed discussion (anamnesis) as well as through physical and laboratory medical examinations.

If necessary, he will refer the patient to a specialist - an ear, nose and throat specialist. Depending on the (suspected) cause of the ageusia, other specialists can be called in, for example a neurologist (neurologist) or radiologist (x-ray specialist).

In some cities there are even "centers for taste disorders". Such a center is often a special outpatient clinic attached to a hospital, which specializes in the diagnosis and treatment of taste disorders such as the rare ageusia. As a rule, it is worthwhile for those affected to take a further journey to get there if necessary.

Medical history (anamnesis)

At the beginning of the visit to the doctor, there is a detailed discussion between the patient and the doctor, which can provide important information about the cause of the taste disturbance. Your doctor will ask you a variety of questions. For example:

• Do you no longer taste anything (ageusia) or has the taste sensation changed in some other way?
• How long have you had the taste disturbance?
• Did the taste disturbance occur suddenly or did it come slowly?
• Is the taste disturbance always present or only temporarily?
• In addition to the taste disturbance, do you also have problems with smelling?
• Do you take any medicine? If yes, which?
• Do you smoke? Do you drink alcohol? How much each time and since when?
• Do you have any previous illnesses (e.g. diabetes mellitus, autoimmune diseases)?
• Have you suffered a skull injury in the past?
• Have you received / are you being treated with radiation or chemotherapy because of cancer?
• Have you had any head and neck surgery?
• Aside from the taste disturbances, do you have any other complaints such as dizziness, visual disturbances, headaches or sensory disturbances in your arms or legs?

Physical examination

In the next step, the doctor thoroughly examines the mouth, nose and throat. In this way, many obvious causes of ageusia, such as inflammation, can be identified. In addition, the doctor palpates the lymph nodes in the head and neck area. If you are swollen, this can indicate an inflammatory disease, among other things.

Because the cause of ageusia sometimes lies in the area of ​​the cranial nerves or the brain, the doctor will also carry out an orienting neurological examination: Simple tests are used to check whether there is a possible failure of cranial nerves or brain functions.

Taste tests

To clarify a taste disorder, special tests are carried out in the next step that check the taste (gustometry). Various methods are available. Here are some examples:

In the context of classic gustometry, test solutions of different flavors (sweet, sour, etc.) can be administered one after the other to screen the general (global) taste function (in the whole mouth) - for example as drops on the tongue or as a spray solution in the mouth. The patient should try to identify them correctly.

You can also test different dilutions (concentrations) of each solution of a flavor. This not only makes it possible to determine whether the patient can identify different flavors, but also uses the dilution to determine how good the taste sensation is for the particular flavor (intensity estimation).

Sometimes the taste in the whole mouth is not disturbed, but only in a certain area - for example, because the cranial nerve supplying this area is damaged. This regional taste ability can be tested, for example, with highly concentrated taste solutions that are specifically applied to the area to be tested on the sticking out tongue. The patient should then display his taste perception on a board. He is not allowed to speak and he has to keep his tongue very still so that the test solution does not spread to other taste areas - the test result would then be falsified.

Another way to test regional taste is electrogustometry. A very low current is applied to the surface of the tongue. It irritates the taste buds (like a flavoring substance) and normally triggers an acidic or metallic taste perception in the patient. The taste threshold is then determined separately for each half of the tongue - i.e. the slightest stimulus (in the form of the lowest current strength) that evokes a taste perception in the patient.

Further investigations

In addition to these special tests of the sense of taste, further examinations are often necessary in order to be able to identify a cause of ageusia (or other taste disorder). These include:

• Blood tests, e.g. if you suspect a vitamin, zinc or iron deficiency, as yet undiscovered diabetes, liver disease or infection (search for specific antibodies against the pathogens)
• Computed tomography (CT) and / or magnetic resonance imaging (magnetic resonance imaging, MRI)
• Measurement of saliva production
• Fine tissue (histopathological) examination of biopsies (tissue samples) of the tongue and oral mucosa
• dental examination

Therapies

For a taste disorder such as ageusia, treatment is based on the underlying cause. A lot of patience is usually required from the patient. The taste system has an exceptionally high ability to recover spontaneously after damage. If the cause of the taste disturbance is not a simple cold or something similar, it can be temporary and harmless, but recovery can take a long time (usually months or even years).

Here are some examples of causal therapy options for ageusia:

• In the event of iron or vitamin deficiency, the doctor can prescribe appropriate preparations to compensate. Substitute preparations are also necessary in the case of an underactive thyroid - hormone preparations that compensate for the lack of thyroid hormones.
• A traumatic brain injury - a common cause of taste disorders such as ageusia - is treated depending on the severity, for example with bed rest, pain relievers, or surgery.
• If medication is the cause of the ageusia, the attending physician may, if necessary, suggest discontinuing the preparation - if possible - or switching to another preparation.
• If a drug has caused a zinc deficiency, which in turn causes a taste disturbance, a zinc preparation makes sense. In other cases of taste disorders, zinc intake is sometimes recommended, even if its effectiveness has not always been proven.
• If a tumor is the trigger for a taste disorder such as ageusia, conservative treatment with medication, radiation or surgery may be indicated.
• Other underlying diseases that are associated with ageusia or another taste disorder (such as diabetes, multiple sclerosis, etc.) must also be treated professionally.

Ageusie: You can do that yourself

In case of ageusia due to dry mouth, saliva-stimulating agents, so-called sialogoga, can help. They are not only available as a preparation in the pharmacy (e.g. pilocarpine tablets) - the production of saliva, for example, also stimulates chewing gum, candy, lemon juice and other acidic juices.

In some people with functional ageusia, there is still a slight residual perception of taste stimuli. Seasoning dishes can be particularly useful for them. A healthy, varied diet is generally advisable in order to prevent deficiencies which in turn can impair the sense of taste.

Anyone who eats too little due to ageusia and has therefore already lost a lot of weight should go to a nutritional consultation.

In the case of all taste disorders, it is advisable to avoid nicotine and other substances that impair taste. Your doctor can advise you on this.

Pay attention to proper oral hygiene (regular tooth brushing, use of dental floss, etc.). This helps to prevent infections (e.g. with bacteria or fungi) that can damage the mucous membrane (and thus also the taste buds).

Taste disorders such as ageusia can be psychologically very stressful - especially if they are permanent and / or the cause cannot be determined. Exchanging ideas with other people affected can then be beneficial. Professional psychological / psychotherapeutic help may also be advisable.

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