What Is Wound Exudate and Why Do Our Bodies Produce It?

Wound exudate is a fluid that our bodies excrete through wounds that can help to determine if there are any complications, like an infection or an issue with the healing process.

Written and verified by the doctor Leonardo Biolatto.

Last update: 27 May, 2022

Wound exudate is a combination of substances and elements that our bodies excrete through a wound or during an inflammation process. Usually, people refer to this as what comes out of a cut, the liquid of the wound, or wound leakage.

Wound exudate may seem unpleasant and even be worrying in some cases. The reason for this is that it can vary, as can the wound itself. But, because of that, its characteristics can give a lot of vital information.

Besides, this combination of substances fulfills a very important role in the healing process. In this article, we’ll explain what wound exudate is, what it’s comprised of, and the different types that exist.

What is wound exudate?

Wound exudate is a fluid. The body produces it in different colors and viscosities, and it’s made up of several substances. The word exudate itself refers to the liquid that filters through the blood vessels. It’s similar to plasma. In fact, it’s the liquid part of the blood, with a high concentration of proteins.

This liquid filters through the blood capillaries. The filtrate depends on the permeability and the difference of pressures of the liquid, both between the cells and outside of them. The body typically reabsorbs the filtrate through the capillaries.

Also, the small amount that the circulation system doesn’t reabsorb passes into the lymphatic system. From there, it returns back to the blood. This way, the body maintains a state of balance between the liquids throughout the whole body.

The body produces the wound exudate through the inflammation process that’s triggered by a wound. When the body suffers an attack, it then releases a series of substances that increase the permeability of the capillaries.

When they become more permeable, the cells of the immune system and the pro-inflammatory substances can travel to the area of the injury. For that reason, the body will produce an excess of liquid that it filters through the wound.

Why does the body produce wound exudate?

The body produces wound exudate as a response to impact. According to a publication in the World Union of Wound Healing Societies, it contains several substances that fulfill important functions in the healing process.

First of all, water, electrolytes, and sodium are the fundamental components. In the wound exudate, we can also find immune system cells (leukocytes), proteolytic enzymes, and inflammatory mediators.

These mediators are substances that have the task of stimulating even more immune system cells to migrate to the wound area. The exudate contains growth factors that have the job of stimulating cellular proliferation to heal the wound.

However, the exudate can have other effects. In wounds that don’t heal and become chronic, this compound contains more inflammatory mediators and proteolytic enzymes.

Main types of exudate

There are different types of wound exudate. According to a publication in Wound Source, there are 5 main types: serous, sanguine, serosanguinous, purulent, and hemorrhagic. The body typically produces each one of them at different times in the healing process.

1. Serosanguinous exudate

Serosanguinous exudate is the most common. It has a thin, pink appearance and a watery consistency. This is because it contains small amounts of blood cells interspersed with serous fluid.

2. Serous exudate

Serous wound exudate is a clear liquid. It’s considered to be the body’s normal response to a wound. By doing this, the body is properly following the healing process. This exudate doesn’t hurt nor is it too viscose.

The body produces the liquid because as the skin regenerates, it generates waste, such as dead cells and proteins. The problem is that, if the body produces a lot, it may indicate there’s a problem in the healing process.

3. Bloody exudate

Bloody exudate is a reddish liquid, which has a more intense color than the serosanguinous exudate. The body usually produces this when it’s cleaning the wound or if you move too much, especially soon after it happens.

Normally, the body produces this during the inflammation stage. At that point, it’s common for some blood to leak into the wound. However, if this happens later, when the tissue has already started to regenerate, it’s usually due to trauma to the injury itself.

4. Purulent exudate

Purulent wound exudate has a more viscose and thick appearance. It may have a greyish, green, or yellowish color. This is because it has a higher concentration of white blood cells and bacteria, meaning it’s a sign of an infection.

5. Hemorrhagic exudate

People can confuse hemorrhagic exudate with bloody exudate. However, this type indicates injury to a blood vessel due to infection or trauma. Here, the color is redder and it has a thicker consistency.

Other aspects of wound exudate

There are a few noteworthy aspects that you should bear in mind when it comes to assessing wound exudate. According to a publication in FFPaciente, the color is one of the most important factors that you should consider. Specialists consider a clear or light yellow color to be normal. 

However, if the liquid has a more murky appearance, it may indicate an infection. Especially if it has a green or brownish color. It may also be a sign of necrotic (dead) tissue. A reddish color, as we mentioned above, suggests the presence of blood.

The viscosity of the wound exudate is also a telling sign. When it’s too viscose or thick, it means there’s an infection and a high protein content. However, if the liquid is watery, the protein content is likely to be low.

What influences the amount of exudate?

The amount of exudate also influences the evaluation. When the wound is in the process of healing, it’s normal for the exudate to progressively reduce. However, if it doesn’t heal as it should, then the body may continue to produce the exudate.

When this happens, there’s an excessive amount that causes the inflammation process to continue. Also, humidity conditions can interfere with the healing.

Additionally, many factors can influence the amount of exudate the body produces. The first is the extent of the wound. The larger the surface area, the more drainage the wound produces. The same can be said for the type of wound. Burns, venous ulcers, and inflammations usually have abundant exudates.

Similarly, if there’s peripheral edema or infection, it’s more common for the body to produce a lot of exudate. If the wound is on a leg and the leg isn’t raised, then the liquid tends to come out due to gravity.

Some wounds naturally only produce a little exudate. Like ischemic ulcers, for example. This is due to a lack of blood supply.

Wound exudate is illustrative

What you should remember is that wound exudate is something normal. The body produces it in response to an injury to facilitate the healing and curing process. However, if a wound is chronic, the exudate may have a negative impact on the process.

Also, we should remember that the characteristics of the exudate, like the color and viscosity, are determining factors. They can help you determine whether there’s an infection or the wound is bleeding.