A senior consultant in Oral Medicine at the National Hospital, Abuja, Dr Ekhosuehi Agho, speaks to EMMANUEL OJO on the causes, diagnosis and management of loss of taste or an altered sense of taste
Can you describe what a loss of taste or distorted sense of taste is about?
Talking about the loss of taste, it can be total or partial or what we refer to as an altered sense of taste. We have what we refer to as dysgeusia. It (dysgeusia) means that there is an altered taste or altered sense of taste. Then you have what is called ageusia, meaning that there is no taste at all or there is a complete loss of taste.
When can one be said to have a distorted or altered sense of taste?
So, when you talk about taste abnormality, when we say that there is a reduction in the sense of taste, that is dysgeusia, which refers to the fact that there is an altered taste but when there is no taste at all, that is what we refer to as ageusia, referring to a complete loss or sense of taste.
There is also what we call hypogeusia. When we say hypogeusia, we mean that there is a diminished sense of taste. There are situations when one could also have hypergeusia which talks about increased sensation or increased sense of taste.
It can actually be referred to as a (medical) condition. When a patient says he does not taste well or he does not have a good sense of taste or he has an altered sense of taste, it is a clinical condition that the patient can present at the clinic, saying that he is not tasting well. The patient can also present that the way things taste in the mouth is funny or has some form of metallic taste in the mouth.
What causes the condition of loss of taste or altered taste in the mouth?
Basically, a lot of things can cause an altered taste in the mouth which we call dysgeusia. It could be as a result of a disease condition that is ongoing in the body and it could be a condition that is just within the mouth itself, whether it is of a primary or secondary cause.
The causes of dysgeusia can be divided into different categories. The first is infection. Under infection, one of the most common causes of dysgeusia is COVID-19 because it is taken as one of the presenting symptoms. It can also be through infections affecting the mouth, such as bacterial, viral and fungal infections. All these can cause dysgeusia.
Another cause of the condition is drugs; drugs such as metronidazole, that is, common drugs like Flagyl can cause dysgeusia. Some hypertensive drugs too can cause dysgeusia. Some diuretics can also cause it.
We can also see dysgeusia in patients that are undergoing treatments for head and neck cancers using chemotherapy, which is part of the side effects. Then, other conditions that can also cause dysgeusia include dry mouth; what you can also call xerostomia. It can also cause dysgeusia.
Are there other causes apart from these?
It can also be caused by the deficiency of vitamins or minerals such as deficiency of vitamin B. You also have conditions that cause neck damage such as Bell’s palsy, which can also result in this condition. Also, neurological diseases or neurological disorders such as Parkinson’s disease and multiple sclerosis can also be associated with dysgeusia. Other causes are diabetic disorders such as diabetes mellitus, and hypothyroidism. Also, some kidney diseases also cause dysgeusia.
Pregnancy can also cause dysgeusia. Sometimes, as people age, there is also a gradual change in the sensation of taste. So, ageing is also a factor. It is also important to note that taste disorder can also be associated with loss of smell, which we call anosmia. So, sometimes, the patient may have anosmia and could be presenting dysgeusia. So, those are the very major causes.
Another cause can be acid reflux. There is what we call Gastroesophageal reflux disease which is a result of regurgitation of the stomach contents back into the mouth. When stomach acid enters the mouth frequently, it can also alter taste.
Are there also factors resulting from the consumption of hot foods or liquids?
No. In the oral cavity, for instance, we have different nerve endings. We have different nerve endings for taste which are called specialised nerve endings, then, we have for proprioception and we have for pain. So, the nerve that supplies the tongue with taste is different from the ones that bring about sensation.
When you take something hot; that is more or less like a burn, it is different from the tasting. It is different from taking something that is sour. So, feeling pain from burns is different from having an altered taste or loss of taste. So, when we talk about local trauma, when we talk about maybe heat, excessive heat, chemical burns and so on, it has not been reported to be the cause of dysgeusia. It may cause pain, cause discomfort and inability to eat, but not dysgeusia.
What are the early symptoms that hint that one may be having an altered or distorted taste?
Okay, talking about how a person would know that he has dysgeusia, one of the ways to know is that the food that tastes good will start tasting bad or tasting funny. So, foods that are salty no longer taste salty. Also, food begins to have a metallic or bitter taste. Sometimes, patients will also feel a taste in their mouth even when they are not eating anything. Those are the major things that the patient will usually talk about. If they take something sweet for instance, it wouldn’t appear to be sweet. So, there’s an alteration of the normal.
Are there complications that come with this condition?
As I said earlier, dysgeusia can be primary or secondary. When I say secondary, it means that there is an underlining condition somewhere that is causing it. So, some of those underlying conditions, for example, can be related to drugs, maybe it’s the drug that the patient is taking that is causing it. Also, a patient that has head and neck cancer and is undergoing chemotherapy can present with dysgeusia and that means it is from the (side) effect of the chemotherapy. Another one is someone having diabetes; he may present with dysgeusia. Maybe a patient that’s on a diuretic (medication) may also present with dysgeusia. Though a patient that has Parkinson’s disease will present, it can be a symptom of an underlying disease.
How do you diagnose this condition?
Diagnosis of dysgeusia is easy. What we usually do is that there are some investigations that we make the patient undergo. One of the investigations that we can ask the patient to undergo is a test for a full blood count. We could ask the patient also to do vitamin B12 level. If we suspect any other underlying infection, we may ask the patient to do it and if the patient comes to the dental clinic, we can check for taste. There is what we call a taste test.
How do you go about the taste test?
What we do is that we get the patient blindfolded; then, we get different items with different tastes and ask the patient to try to identify what is what. For instance, we may take a drink that is sweet and put some on the patient’s tongue and ask the patient what they tasted. If it’s a sweet substance and the person is saying bitter, then, we know that there is an alteration. If it’s something sour like lime for example and the patient cannot say that it is lime, then we know that there is a problem. Basically what we do is a ‘taste test.’ We do a taste test for sweet, a taste test for sour, and a taste test for bitter.
At the point where distorted taste has been diagnosed, how then is it managed?
Once a diagnosis is made, for us, we treat according to what the patient presents. We individualise treatment. It’s not a generalised treatment or the way we treat everybody. For instance, if a patient is having dysgeusia to a drug, we counsel the patient that it is the drug that he is taking that is leading to that. If it is as a result of head and neck cancer resulting from chemotherapy, there are other things that we can also do. So, basically, what we usually do for patients that have dysgeusia generally is that we give them vitamin B supplement which has been found to work for patients that have dysgeusia but it is very important for us to find the underlying cause and we go ahead to do that and once you have the underlying cause treated, the dysgeusia may just go, but if it’s primary dysgeusia, the use of vitamin B12 supplement may work for the patients.
Is it a condition that can be inherited or genetically transferred?
No, it cannot be inherited and cannot be genetically transferred. It is important to note that once you can get the root cause of it, you can treat it and it will be gone. Most of the time, by the time you give patients vitamin B12, they will be fine.
As an oral condition, is it communicable?
No, it is not a non-communicable disease. It is non-communicable. You can’t transfer from husband to wife or from father to child.
Does the condition affect the appetite of the patient?
Yes, it does. It has a correlation with appetite. When somebody is having a funny taste, metallic taste and all that, the person will not want to eat and would have a poor appetite. Yes, it has a correlation with appetite. When you eat and you don’t enjoy it or you are not feeling the food that you are eating, you won’t want to continue eating and your appetite will be poor. So, it does affect the appetite.
I won’t say it has a direct correlation with weight loss but if a patient is having dysgeusia and the patient is not feeding well, as a result of the disorder or the altered sensation that he or she is feeling, definitely, there will be weight loss. So, it’s not like a direct association but it can and when it persists and the patient is not eating, definitely, the patient will have weight loss. That’s the truth.
The taste buds are not just located on the tongue alone. There are taste buds on the palate. You also have them in the pharynx; that’s why you find out that sometimes when one is taking a drug and he says that he doesn’t want it to touch the tongue, but by the time it gets to the throat, the person will still feel that it’s bitter and it’s because of the presence of some taste bud there. It depends on what is causing the injury, the degree of the injury and the area affected.
For instance, if it’s an injury just affecting the tip of the tongue, there will be no problem with tasting. However, if the injury is affecting more than two-thirds of the tongue; for instance in a situation where people are fighting and one person bites the other part off, the other part of the tongue can still taste for some things. So, trauma has not been recorded as any cause of dysgeusia. For chemical burns, yes, there may be pain. When there is pain in the oral part, the person may not be able to eat but it’s different from the fact that the person is not able to taste the food.
What about alcohol? Does it have any effect on taste sensation in the oral cavity?
Yes. Also, HIV/AIDS can cause dysgeusia too. So, alcohol and tobacco smoking can cause dysgeusia in a way. It can because alcohol can lead to ‘malabsorption syndrome.’ Chronic alcoholism should be able to cause dysgeusia.
Is the condition in any way linked with depression?
Yes. Wh en it becomes chronic; when I say chronic, I am talking about the fact that dysgeusia now exists for a very long time. For anything that is chronic, yes, there can be a link to depression. Yes, it can. For example, if someone is having altered taste, the person won’t be able to eat or eat well and when it lasts for a month, two months and even three, depression can set in. When dysgeusia becomes chronic, the person can have depression.
