The Four Humours: History of Medicine for Kids & 6 Fun Facts

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Updated on: Educator Review By: Michelle Connolly

Introduction to The Four Humours

This article will teach you all about the Theory of the Four Humours which created the medical belief in Humourism. Humourism was the belief that your body’s health and temperament was affected by four liquids in the body. This theory on how your physical and mental health were affected by your humours affected medicine for over 2000 years. We now know that the Theory of the Four Humours was incorrect but has some interesting ideas about balanced diet and health. So, what are the Four Humours, who came up with the theory, and how did it affect medicine? Read on to find out!


Click on the questions below to skip right to what you need to know!

What is the theory of the Four Humours?

The Four Humours are Blood, Black Bile, Yellow Bile, and Phlegm. The Theory of the Four Humours was that these four liquids in your body could affect your physical and mental health through imbalance. These ‘humours’ were thought to be created in the liver and transported through the body through the blood stream.

Physicians throughout history used the Four Humours as a method to diagnose illness, they did this by observing their patients symptoms and behaviors. The Four Humours were also studied through urine. Although they are no longer checking your humours Doctors still test your health through your urine today.  

These humours all had traits related to them, seasons associated with them, and ways in which they affected people. Some people were believed to favour one humour all the time by nature, such as naturally sad people favoured black bile. Different humours were even known to be in abundance through different life stages. Lets look at each humour in a little more depth.

Was the theory of the Four Humours correct?

No, it is important to remember that although the Theory of the Four Humours was believed for over 2000 years it has been disproved. However, it is still worth learning about to gain an understanding of what was previously believed by physicians. This theory also teaches about how long standing thought can also be challenged with new findings. We are always learning!

If you want to learn how the circulatory system really works, check out our video!

What are the Four Humours?


Blood was seen as the most important of the Four Humours, it was described with the traits hot and wet. People a higher amount of blood in their system all the time were described as being friendly, active and sociable. Blood was associated with springtime and with liveliness as it was an invigorating humour. It was also believed that you would have more blood in the body when you were younger as young people were happy and energetic in nature.

Blood played the role of creating heat for the body and was thought to contain your life energy.

Black Bile

You may have heard of the word ‘Melancholy’, meaning sad, this term for sadness comes from the Greek term for Black Bile. Black Bile was described with the traits cold and dry and was associated with Autumn (Fall). It was thought that when you approached middle age you would have an increase in Black Bile as people in that time were known for worries or stress. It was believed that if you had an excess of Black Bile you would become sad or even depressed.

Black bile was thought to strengthen bones and control metabolism.

Want to know about how bones are really formed and how they work? Check out this video:

Yellow Bile

Yellow bile was described as hot and dry, and was associated with aggressive or erratic behaviour. In extreme cases they believed that too much yellow bile could cause madness. Yellow bile was associated with summer time, so the body would produce more at that time of year. Early adulthood is when it was believed you had the most Yellow Bile in your system. This is related to aggression and determinedness but also courage as you have things to achieve at this life stage.

Yellow bile was key to digestion of food and helped the work of the lungs.


Unlike Phlegm we refer to in medicine today the humour of Phlegm included all clear substances secreted by the body, for example, saliva. Phlegm was described as cold and wet and was associated with Winter. Having an excess of Phlegm was associated with relaxed and indifferent behavior. The life stage of Phlegm was older people who were more relaxed in later life.

Phlegm was believed to keep the body moist, and transport vital nutrients around the body while removing impurities.

How are the four elements related to the Four Humours?

The four elements Earth (associated with Black Bile), Air (associated with Blood), Fire (associated with Yellow Bile), and Water (associated with Phlegm) were part of the world understood by historical people. These elements were applied to the Four Humours to make sense of the smaller world that made up the human body. This was a way for people to understand how the body worked through their understanding of how nature worked. As nature was much easier to observe than the inner workings of the body.

The Four Humours Diagram

This diagram shows the relationship between the humours and their associated traits, diagrams just like this one were used by doctors to diagnose and treat their patients. Many medical texts written throughout history use this diagram to explain the Four Humours and show their links to seasons, temperament, temperature, and elements.

Diagram explaining the four humours

How to Balance the Four Humours

Nowadays we know that eating healthy and having a balanced diet helps our physical health. The Theory of the Four Humours was the first time humans tried to balance their diet for their health. There were many ways to balance the humours including medicines, food, exercise, and other medical treatments.

The Theory of Opposites was a big part of treating the four humours as it was believed to be possible to put the humours back in balance by eating or drinking something that has the opposite traits. Such as hot and wet foods to treat melancholy caused by excessive Black Bile, as Black Bile was cold and dry.


This one had a simple solution in the form of a practice called blood-letting, which was performed by barber surgeons. Barber Surgeons were people who worked as barbers cutting hair but also did minor surgery as surgery was seen as work done with your hands and therefore unskilled work! I’m sure we are all very grateful that we no longer think this way. Another gruesome way to reduce blood in the body was by using leeches, also doesn’t sound very fun.

It was believed that by letting out some blood from the body a new balance could be reached. However, we now know that blood is best kept inside the body and that blood-letting would only make patients weaker rather than cure them.

Alternatively, food was a key way of balancing the humours, the Theory of the Four Humours was humans first development of a balanced diet system. As blood was seen as hot and wet you could balance out the system by eating foods that were cold and dry. Or if you needed more blood humours you could eat hot and wet foods to help you with that.

Black Bile

Black Bile was removed from the body through laxatives which were usually herbal remedies. Those who wanted to reduce Black Bile through diet ate foods that were hot and wet to balance out their humours.

Yellow Bile

People suffering from excess Yellow Bile were given medicines to make them vomit as it was believed this would get rid of the excess bile. The diet of someone who has excess Yellow Bile consisted of cold and wet foods that would counteract the hot and dry effects of Yellow Bile.


Phlegm was also treated with laxatives and medicines to make you vomit to get rid of the excess. Those suffering from excess Phlegm would eat hot and dry foods to combat the cold and wet Phlegm.

Who discovered the Four Humours?

Hippocrates and the Four Humours

The Theory of the Four Humours was first developed by a physician called Hippocrates, who finally out into writing the thoughts of the time on how the body worked.  Many physicians of the time had discussed the links between the balance in the body and health. Hippocrates wrote doctrines (Medical texts) on the Four Humours outlining how they contributed to physical and mental health.

How to Pronounce Hippocrates

Despite what it looks like his name isn’t pronounced Hippo Crates, like a company that sells boxes to Hippopotamuses.

The best way to try is to break it down into sections like this:

Hi – ppoc – ra – tes

Pronounced: “Hih” – “pock” –“rah” –“tees”

Hear how Hippocrates is pronounced here.

Fun Facts about Hippocrates

  • Hippocrates created an oath for doctors called the ‘Hippocratic Oath’ which vowed to protect patients and cause no harm. A similar oath is used by doctors today and is still called the Hippocratic Oath.  
  • Hippocrates’ father was also a physician.
  • Due to his contributions to understanding medicine, Hippocrates is referred to as the ‘Father of Medicine’.

Galen and the Four Humours

Another important person in the history of the Four Humours is Galen, a physician who lived around 200 years after Hippocrates. The Four Humours Theory was still being practiced by physicians. Galen was the one who assigned each of the humours to a human emotion, furthering the theory and adding to the work of Hippocrates.

Fun Facts about Galen

  • Galen was the person who discovered that the brain control the body, not the heart.
  • Galen used animals to try and find out how the anatomy of humans worked.
  • Galen’s model of human anatomy was believed to be correct until the 1500’s (that’s 1700 years!).

Although, both Hippocrates and Galen were responsible for the first writings about the Four Humours, and the wide-spread popularity of the theory. If we ask the questions who invented The Four Humours Theory? We must credit the physicians of the time which worked to develop the theory which are less well known but also posed theories and ideas. Often in history there is no clear cut answer but its interesting to look into key figures that affect the events.

How did the Four Humours develop medicine?

The Four Humours Theory first written about in 400 BCE was only conclusively disproved in the 1850’s. This means that it was used in medicine for over 2200 years. It is easy to see why this long standing belief in an incorrect system may have been detrimental to progress. However, this method helped to develop healthy habits of moderation. It is still important today that we only eat certain foods in moderation and maintain a balanced diet.

The use of the Four Humours also meant that doctors developed methods of observing their patients which are still used today. Observation of symptoms is still a key skill doctors use today, including urine samples, asking about diet, and checking temperature. All these observational tools are very helpful in finding out what’s wrong and they started with the work of Hippocrates and Galen who developed the Four Humours Theory. Even though they were wrong they have lessons to teach us today.

Check out our video on how to keep your body healthy through a balanced diet.


The Four Humours was a theory on how the body worked that was popular for over 2000 years. The Four Humours were blood, black bile, yellow bile, and phlegm. It was believed these humours in your body had to be kept in balance to keep you healthy. To keep them balanced people would eat foods with properties different to the humour they had too much. For example if you had too much black bile you had to eat hot and wet foods that would balance out the cold and dry bile.

Now we know that the Four Humours don’t exist but we know we must still keep a balanced diet to keep our bodies healthy.

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