Tongue and Mouth: A Mirror of Digestion and Inner Health

Farzollah Gholizadeh and Fariba Bayrami

What messages do colour, coating, moisture, cracks and changes in the mouth give us?

When you wake up in the morning, before brushing your teeth, look at your tongue in the mirror for a few seconds.

What colour is it? Pink and glossy, or white, yellow, red or dark? Is there a coating on it? Is that coating thin or thick? Is the tongue dry, or overly moist? Are there cracks, swelling, tooth marks, sores or spots? What taste is in your mouth? How is your breath?

You might think these are only matters of oral hygiene. Yet in Sina–Unani medicine and in many schools of traditional medicine, the tongue and mouth are among the most important visible parts of the body for understanding a person’s inner state.

Today’s medicine also knows that some general illnesses, nutritional deficiencies, hormonal (endocrine) problems and digestive diseases can show signs on the tongue and the lining of the mouth.

So sometimes we only need to open our mouth, and the body itself offers clues about its inner state.

But let’s keep one principle in mind from the start:

The tongue does not diagnose disease on its own; the tongue gives clues.

The art of diagnosis is being able to read all those clues together.

Why is the tongue important for understanding the body’s state?

The tongue is one of the visible organs of the body with the richest nerve and blood supply, and it is in constant interaction with saliva, food, the microorganisms of the mouth and the body’s internal environment.

The colour and appearance of the tongue can be influenced by many factors:

• The body’s fluid balance
• Saliva
• Diet
• Oral hygiene
• The oral microbiota
• Medicines
• Cigarettes and tobacco products
• Infections
• The body’s general condition
• Some nutritional deficiencies
• And some diseases

In Sina–Unani medicine, too, the tongue and mouth are regarded as part of a wider system: “dalail and alamat” (evidence and signs).

Physicians didn’t only ask about the colour of the tongue; they paid attention to colour, moisture, dryness, coating, consistency, movement, sensation, taste in the mouth, saliva and breath odour, and assessed them together with the pulse, urine, stool, appetite, thirst, sleep and other signs.

The tongue: a mirror of digestion

One of the most important connections in Sina–Unani medicine is the relationship between the stomach and digestive system and the tongue and mouth.

According to the old physicians, if digestion does not happen properly, its effects can appear in appetite, belching, bloating, the taste in the mouth, breath odour and the quality of the tongue.

Traditional texts also point to the effect on the mouth and tongue of vapours and matter rising from the stomach.

Put simply:

Sometimes the problem is not only on the tongue; its root must be looked for further down, in the digestive system.

That is why, in a traditional examination, when a practitioner sees an abnormal tongue, they may ask:

How is your appetite? Do you feel heavy after eating? Are you bloated? Do you burp often? Do you have heartburn (reflux)? What taste is in your mouth in the morning? Is there constipation or diarrhoea?

These questions are not random; the tongue should be read together with digestion.

What does a healthy tongue look like?

The appearance of a healthy tongue varies from person to person, but a normal tongue generally:

• Has a pink colour that suits the person’s natural mucosal colour.
• Is relatively moist.
• Moves normally.
• Has natural papillae (small bumps) on its surface.
• May have a thin, limited coating.
• Shows no lasting sores, swelling or unusual change in colour.

The important point is this:

“A completely uncoated tongue” is not necessarily a measure of health; a thin, natural coating on the tongue can be part of the mouth’s normal state.

What really matters is change compared with the person’s usual state.

The first sign: the colour of the tongue

Colour is one of the first things noticed in a tongue examination.

But the colour of the tongue alone is not enough to diagnose a disease.

A pale tongue

In the logic of traditional medicine, pallor can be associated with cold, weakness and a decrease in the quality or quantity of the blood.

In today’s medicine too, if the tongue and other mucous membranes become unusually pale, especially together with tiredness, weakness, dizziness or shortness of breath on exertion, the state of the blood and anaemia are among the things to investigate.

That is:

Pallor is a clue; it is not a definitive diagnosis of anaemia.

What does a red tongue tell us?

In traditional medicine, increased redness of the tongue, especially together with dryness, thirst and a feeling of heat, is interpreted more in the direction of increased heat.

But a red tongue can have other causes too.

Some inflammations, infections, nutritional deficiencies and other conditions can also change the colour of the tongue.

So the practitioner should not only ask “Is the tongue red?” but also:

Is it red and dry, or red and moist? Is there a coating or not? Is the whole tongue red, or only part of it? Is there also burning or pain?

These small differences can change the meaning of the sign.

A yellow tongue: bile, or something else?

In the logic of humoral medicine, yellowness can draw our attention to the quality of the bile and to increased heat and dryness.

But yellowing of the tongue tissue itself must be distinguished from a yellow coating on the tongue.

These are not the same thing.

The tongue coating can also change colour because of bacteria in the mouth, hygiene, dry mouth, food, smoking and other factors.

Even this simple point shows why tongue diagnosis is much more than seeing a colour.

The coating: perhaps more important than colour

One of the most interesting parts of the tongue examination is the layer on the tongue, the coating.

The coating is made up of various substances, cells, bacteria and debris collected on the surface of the tongue’s papillae.

In traditional medicine, not only the colour of this coating matters.

The practitioner should look at:

Is it thin or thick? Dry or moist? Does it clean off easily, or is it sticky? Does it cover the whole tongue or only part of it? Is it white, yellow, or another colour? Does it form again quickly after cleaning?

So two people can both have a “white tongue”, yet their situations may not mean the same thing.

A white tongue doesn’t always mean the same thing

This is one of the common mistakes on social media.

It is not possible to link every white tongue to a single disease, to fungus or to a stomach problem.

A white coating can form for different reasons.

In the logic of traditional medicine, whiteness together with cold, moisture, a feeling of heaviness and clear digestive complaints carries a different meaning from whiteness seen together with marked dryness.

On the other hand, a white coating that can be wiped off, together with certain complaints, may raise the question of investigating some oral conditions, including fungal infection.

So in the science of signs:

Do not assess colour separately from thickness, moisture, location and accompanying signs.

A dry tongue: not just thirst

Dryness of the tongue is one of the important signs.

Sometimes the cause is simple:

The person hasn’t drunk enough water, has breathed through the mouth, has been in a dry environment or has talked for a long time.

But persistent dryness of the mouth and tongue can also be associated with other factors such as:

• Reduced saliva production
• Some medicines
• Advanced age
• Some salivary gland diseases
• Some systemic diseases

In traditional medicine too, tongue dryness gains importance, together with thirst, heat, the pulse and other signs, for understanding an increase in dryness or heat.

Saliva: one of the signs we pay little attention to

Saliva is not only for keeping the mouth moist.

It plays a role in chewing, swallowing, speaking, protecting the oral environment and protecting the teeth.

In the science of signs, attention should be paid to the amount and quality of saliva.

Is the mouth constantly dry? Does saliva collect excessively? Is it thick or watery? Is it different in the morning? Does it come with an unusual taste in the mouth?

In traditional medicine, the quality of saliva is assessed together with digestion and temperament.

Sometimes what a person thinks is a “tongue problem” is actually more related to a change in saliva production.

What do tooth marks on the edges of the tongue tell us?

Sometimes the tongue is wider or swollen, and the marks of the teeth remain along its edges.

In traditional medicine and some schools of Eastern medicine, this appearance is considered together with other signs and can be interpreted in terms of moisture, digestion and the quality of the body’s functioning.

But in today’s medicine, a scalloped tongue can also have different causes and does not on its own point to a particular disease.

So here too, the more important question is:

What other signs come with it?

Cracks in the tongue: not every crack is a disease

Some people are born with a grooved or fissured tongue, and this can continue for years without any problem.

But if the cracks come with dryness, pain, inflammation, a change in colour or a new change, the situation is different.

In traditional medicine too, the type and depth of the crack, whether the tongue is dry or moist, and other accompanying signs matter in interpretation.

So simply seeing a crack is not enough to draw a conclusion.

A smooth, shiny tongue: think about nutrition too

Sometimes the tongue loses its natural bumpy texture and looks smooth, shiny or more sensitive.

This kind of change can be seen in some nutritional and blood conditions.

In a clinical assessment, the status of iron, vitamin B12, folate and some other factors may come up.

If this appearance comes with pallor, tiredness, weakness, a burning tongue or other signs, it is worth investigating in more detail.

But again:

A particular deficiency cannot be fully diagnosed from the appearance of the tongue alone.

Burning of the tongue and mouth

Sometimes the tongue looks almost normal but the person complains of burning.

A burning sensation can be associated with different causes such as dry mouth, local irritation, some nutritional deficiencies, oral problems, some diseases and even nervous and psychological factors.

In traditional medicine too, we should look at how the burning relates to heat, dryness, thirst, the colour of the tongue and digestion.

So what the patient feels matters as much as how the tongue looks.

The taste in the mouth: a forgotten sign

Bitterness, sourness, unusual sweetness, saltiness or a metallic taste in the mouth can offer some clues.

In Sina–Unani medicine, a change in taste is assessed together with appetite, thirst, digestion, the tongue and other signs.

But today’s medicine also knows that a change in the sense of taste can have very different causes: from medicines and oral diseases to infections and some general disorders.

So a “bitter mouth” on its own does not mean a particular liver or gallbladder disease.

Bad breath: not always a stomach problem

One of the most common beliefs is:

“Bad breath comes from the stomach.”

Digestive problems can sometimes play a part, but in most cases the source of bad breath is the mouth itself.

Microbial plaque, the tongue, gum disease, dental problems and dry mouth are important causes.

Post-nasal drip and some nose and sinus problems can also play a part.

So if a person has their stomach treated for years for bad breath, but the tongue, teeth, gums, saliva and throat are never examined, the real cause can be missed.

The gums speak too

Oral health is not limited to the tongue.

Healthy gums generally don’t bleed often, don’t swell and don’t recede from the teeth.

Recurring gum bleeding calls for examining the gums and oral hygiene rather than being treated as a simple sign of temperament.

But if unusual gum bleeding comes with easy bruising or other bleeding in the body, a more thorough assessment also becomes important.

Mouth sores and ulcers

Occasional mouth ulcers are very common.

But if mouth sores recur often, are numerous, very large or long-lasting, or come with other signs in the body, they should be examined more carefully.

Some digestive, inflammatory and immune diseases and nutritional deficiencies can occur together with mouth sores.

In traditional medicine too, it is not only the location of the lesion that matters in mouth sores; heat, colour, pain, moisture, discharges and the body’s other signs are also taken into account.

Mouth and gut: a connection sometimes seen on the tongue

The relationship between the digestive system and the mouth is not only a traditional concept.

Today we know that some diseases of the digestive system can also show signs in the mouth.

For example, in some inflammatory bowel diseases, coeliac disease and absorption disorders, changes can be seen in the mouth or on the tongue.

This does not mean a bowel disease can be definitively diagnosed by looking at the tongue.

The right meaning is:

Sometimes the mouth is the first place that makes us ask more questions about the digestive system.

The tongue and blood sugar

Diabetes and long-term high blood sugar can also affect the oral environment.

In people with diabetes, dry mouth, a greater tendency to some infections and gum problems matter more.

If constant dry mouth comes with excessive thirst, frequent urination, tiredness or unusual weight change, it makes sense to have blood sugar checked.

Still, the tongue doesn’t diagnose diabetes; the signs as a whole show the direction of the investigation.

The tongue and the immune system

Some changes in the mouth can also be seen in diseases related to the immune system.

Severe dry mouth, recurring sores or some mucosal changes are sometimes part of a bigger picture.

So if lesions in the mouth keep recurring, they should not always be explained only by “heat” or “cold”.

Temperament is one layer of the diagnosis; a possible disease is another layer.

Mouth, liver and bile

In Sina–Unani medicine, the quality of the bile, digestion and the functioning of the body’s main organs can be considered together with the taste, colour and condition of the mouth.

A bitter mouth, dryness, thirst and some changes in the tongue can, together with other signs, lead a traditional practitioner to examine the state of the bile and digestive system.

But there is a very important point:

A bitter mouth does not equal liver disease.

To assess liver diseases, the signs as a whole and, when needed, tests and medical examinations must be taken into account.

Geographic tongue: odd-looking but not always dangerous

Sometimes some areas of the tongue’s surface lose their natural bumps, and patches with clear borders form whose location and shape change over time.

This condition is known as “geographic tongue”.

Its appearance can worry people, but it is usually benign.

This example shows why recognising signs correctly matters:

Not every unusual appearance is necessarily the sign of a dangerous disease.

Hairy or dark tongue

Sometimes the papillae on the tongue’s surface lengthen and substances and pigments collect on them; as a result the tongue can look dark, or even hairy.

Oral hygiene, smoking, some medicines, dry mouth and a change in the microbial environment of the mouth can play a part.

So seeing a dark tongue is not on its own evidence of an internal organ disease.

A very important principle: separate the “body of the tongue” from the “coating”

Suppose two people have a yellow tongue.

In the first, the body of the tongue itself has changed colour.

In the second, the body is almost normal, but there is a yellow coating on the tongue.

From the point of view of the science of signs, these two situations do not necessarily mean the same thing.

The same applies to whiteness and some other colours.

One of the most important skills in tongue examination is for the practitioner to learn to distinguish:

What is the tongue’s own colour, and what is the colour of the coating on it?

This small difference sometimes completely changes the direction of the interpretation.

Are different parts of the tongue linked to different organs?

Different schools of traditional medicine have paid attention to different areas of the tongue.

Sina–Unani medicine, Traditional Chinese Medicine and other traditional systems each have their own methods of interpreting the tongue, and in some of them different areas of the tongue are considered in relation to different functions of the body.

But this is one of the subjects that must be learned through proper training.

Seeing a spot at one point on the tongue and immediately saying “This area belongs to such-and-such organ, so that organ is ill” is not a scientifically or clinically appropriate method.

Location + colour + coating + moisture + shape + other signs

must be assessed together.

How is temperament understood from the tongue and mouth?

In Sina–Unani medicine, the tongue alone is not enough to determine temperament, but it can be part of the picture.

In general:

Heat can be seen with increased redness, a feeling of heat, thirst or some accompanying signs.

Dryness fits with reduced moisture, a drying surface and sometimes cracking more easily.

Moisture can come with increased moisture in the mouth, softness and some types of coating.

Cold can be seen, together with other signs, with pallor, more moisture or a reduction in some signs of heat.

But determining whether a person is Demevi, Safravi, Balgami or Sevdavi requires observing the whole body and taking the patient’s history.

The tongue is one of the witnesses, not the judge who gives the final verdict.

When should the tongue and mouth be examined?

For better comparison, it is best to observe the tongue under relatively constant conditions.

Coloured foods and drinks, tea and coffee, smoking, some medicines, brushing the tongue and mouthwashes can temporarily change the tongue’s appearance.

So observing in the morning, before eating or drinking and before cleaning the tongue, can be useful for comparing different days.

But a single observation is not enough.

A lasting pattern and change compared with the past matter more than a random snapshot.

Five golden questions when reading the tongue

If you notice a change in the tongue, ask these before drawing a conclusion:

• Has the tongue’s own colour changed, or only the coating on it?
• Is the tongue dry or moist?
• Is the coating thin, or thick and sticky?
• Is this change lasting, or does it appear only now and then?
• What happened during the same period in digestion, appetite, thirst, elimination, energy and other parts of the body?

These five questions move your view from “seeing the tongue” to “reading the tongue”.

Which changes should not be ignored?

It is better for some changes in the mouth and tongue to be examined by a doctor or dentist, especially:

• A mouth sore lasting longer than about two weeks
• A persistent, unexplained white or red patch
• A new lump or hardness
• Bleeding without a cause
• A new problem with swallowing
• Constant pain or numbness
• A marked, lasting change in tongue colour
• Unusual swelling of the tongue
• Severe, constant dry mouth
• A lesion that keeps growing or changing

These situations should not be put down only to temperament or stomach problems.

The big mistake: don’t link every tongue sign to a single disease

Many images are shared on social media:

“If the tip of your tongue is red, such-and-such organ is ill.” “If the edge of your tongue is scalloped, you definitely have such-and-such problem.” “If your tongue is white, you certainly have a fungal infection.” “If your tongue is yellow, there’s a problem with your liver.”

The body is far more complex than these formulas.

One sign can have more than one cause, and one disease can show itself with different signs.

Real diagnosis comes from the combination of signs.

Conclusion: before the body suffers, it sometimes gives signs

The tongue and mouth are in front of our eyes every day, yet we rarely really see them.

The colour of the tongue, the type of coating, moisture, dryness, cracks, swelling, tooth marks, saliva, the taste and smell of the mouth can each be part of a bigger picture.

In Sina–Unani medicine, these signs have been assessed for centuries together with the state of the stomach and digestion, the quality of the humours, the body’s heat and moisture and the functioning of other organs.

Today’s medical knowledge also shows that some blood and nutritional disorders, oral diseases, diabetes, digestive diseases, immune disorders and many other factors can show themselves in the mouth and on the tongue.

But the real secret is not in a colour or a crack.

The secret is in the combination of signs.

A white tongue alone is not a diagnosis. A red tongue alone is not a diagnosis. A crack, a bitter taste or a tooth mark alone is not a diagnosis either.

In the real science of signs, we need to ask:

What changed? Since when? Together with which other signs? And what pattern do all these signs form?

This is where the difference between looking at the body and reading the body appears.

Many people see their tongue in the mirror every day, but far fewer know how to interpret its colour, coating, moisture, shape and other signs together.

And this subject is too wide for all its details to be explained in a single article.

Types of tongue body colour, types of coating, the difference between white and yellow coatings, the thickness and rootedness of the coating, cracks, swelling, tooth marks, spots, sores, moisture, saliva, tastes, the relationship of signs to digestion and the humours, and above all the method of combining several signs to reach a clinical interpretation are each subjects of their own.

The aim of this article was to open a window:

The body sometimes speaks through signs before it speaks through pain; the tongue is one of the clearest places where this conversation can be seen.

For further reading and training

Detailed subjects such as the science of tongue and mouth signs, colours, types of coating, the shape and consistency of the tongue, saliva, taste and smell in the mouth, their relationship to the digestive system and the humours, and how to combine signs for diagnosis are covered step by step and in more depth in Dr Kalan’s “Elaim & Delail” book and course (currently in Turkish).

Want to know your own baseline? Take the free temperament test.

References

• Ibn Sina. Al-Qanun fi al-Tibb; Book One and the sections on evidence, temperament, the mouth, the tongue and the digestive system.
• Al-Razi, Muhammad ibn Zakariya. Al-Hawi fi al-Tibb.
• Jurjani, Sayyid Ismail. Dhakhira-yi Khwarazmshahi.
• Aqili Khorasani, Muhammad Husayn. Khulasat al-Hikma.
• Classical sources of Sina–Unani medicine on signs, digestion, the humours and the states of the tongue and mouth.
• Byrd JA, Bruce AJ, Rogers RS. Glossitis and other tongue disorders. Dermatologic Clinics. 2003.
• Mangold AR, Torgerson RR, Rogers RS. Diseases of the tongue. Clinics in Dermatology. 2016.
• Chiang CP, Chang JYF, Wang YP, Wu YH, Wu YC, Sun A. Atrophic glossitis: Etiology, serum autoantibodies, anemia, hematinic deficiencies, hyperhomocysteinemia, and management. Journal of the Formosan Medical Association. 2020.
• Clinical sources on oral diseases and the oral signs of systemic disease.
• Dr Kalan scientific and educational sources.