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What Factors Affect the Color of Pus?

By Kathleen Howard
Updated Jun 04, 2024
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The biggest factors impacting the color of pus are what the it is made of, particularly where proteins and enzymes are concerned, and why it was created in the first place — which is to say, what sort of disease or condition it’s meant to be fighting. Pus is a thick liquid that humans and many animals produce in response to infection. It is usually white, clear, or yellowish in color, but in some cases it may also appear red, green, or brown. In very rare cases it can also be blue, but this is usually a reaction to only a very few number of pathogens or harmful cells. Color can say a lot about a person’s health and the state of his or her injury, and most medical professionals use the color of pus that is oozing from a wound or internal injury to help make a diagnosis. As such, anyone who is concerned about the colors they see should probably get medical help in order to get to the root of the issue.

Basics of Pus

There are a couple of different reasons why the body produces pus, but almost all of them have to do with infection. The liquid typically pools around the site of an injury or damaged tissue in order to flush out some of the most harmful bacteria. It’s part of the body’s immune defense and its main goal is to help remove diseased or infected cells and other particles. It’s made primarily of neutrophils, which are white blood cells.

The color of pus is largely dependent on where the injury is, what sort of infection is involved, and how long the infection has been going on. Though pus is an important part of the immune response, it is also usually a sign that something is wrong. Color can be a good indication of what, exactly, is amiss, which in turn can lead to more effective treatments and faster healing times.

White and Yellow Varieties

It’s usually considered “normal” for the body to create white, yellow, or clear pus, though this is usually because these are the colors that come about in response to so-called “common bacteria.” This includes Streptococcus pyogenes and Staphylococcus aureus. These strains are responsible for dozens of different infections, ranging from minor skin conditions like pimples to deadly diseases like meningitis.

Simply being common doesn’t make light-colored pus something that should be ignored, though. There are many potentially serious reasons why white, yellow, or clear fluid may be leaking from a wound, and for this reason the condition should often be investigated by a medical professional. Depending on the amount of pus and severity of the condition, antibiotics might be recommended to help fight the underlying infection.

Reddish Tints

Pus can also take on a reddish color. Red pus is usually due to blood mixing with the pus cells. This frequently occurs in urinary tract infections as well as certain skin infections like pimples and boils. The presence of blood does not necessarily mean that the body is having trouble fighting the infection; rather, it more commonly signals that the skin or other bodily tissues have become very irritated.

Green Hues

Green is another common color of pus and might mean one of two things. This pus may be caused by Corynebacterium diphtheriae, which is an uncommon infection of the upper respiratory tract. Pus can also get a green coloring from an antibacterial protein called myeloperoxidase. This brightly colored protein is naturally produced by certain types of white blood cells.

Brown Coloring

Brown pus is usually a sign of an amoebic liver abscess, which is caused by the parasite Entamoeba histolytica. Symptoms of an amoebic liver abscess include abdominal pain, fever, chills, diarrhea, jaundice, joint pain and weight loss. If left untreated, these abscesses can burst and spread the infection to the lungs, brain and heart.

Rare Blue Shades

Blue pus is usually considered very rare, and is the least common of all the different types. This color typically indicates an infection caused by Pseudomonas aeruginosa, which most often infects the urinary tract, pulmonary tract, lungs, kidneys, and blood. Burn wounds are especially vulnerable to Pseudomonas aeruginosa. If left untreated, these infections can become fatal.

Importance of Medical Help

Regardless of its color, pus is not always visible. While it is most commonly associated with open wounds, it can also be found inside the body. Symptoms of pus inside the body, which is also called an abscess, include swelling, heat, pain, redness and compromised function in the area. Many abscesses will not heal on their own, which means that patients should seek professional medical treatment once they notice that something is wrong in order to improve their condition. Pus is the body’s way of protecting itself, but it is also a warning sign that modern medical practitioners can translate and, in most cases, reverse.

Is Yellow Pus a Sign of Infection?

All pus, regardless of color, is a sign of infection. However, not all pus is a cause for concern. For example, most pimples develop a buildup of pus towards their center, which usually appears white in color. However, most pus is actually whitish-yellow upon closer investigation. Either way, pus-filled pimples are a normal skin condition that is rarely a cause for concern beyond aesthetic preferences.

In other situations, pus is a problem because of where it is located and how much is present. Yellow pus that occurs in the mouth, around an injury, or at an incision or injection site usually requires medical treatment. Pus can also develop internally, whether deep under the skin or around organs and tissues. In these circumstances, the patient is unable to detect the pus, but will often see a physician because of other symptoms, such as fever, swelling, pain, difficulty breathing, or other health issues.

What Color Pus Is Bad?

Pus that is white, yellow, or clear in appearance is common and is a normal reaction to typical skin conditions and minor injuries. It is also normal to see pus of a pink or reddish hue because it signifies the presence of blood in the area, which is not uncommon. Be wary of pus with these hues that are:

  • Prolific
  • Unusual
  • Chronic
  • Foul-smelling
  • Accompanied by other signs of infection

Pus that demonstrates these symptoms is almost always serious and should be evaluated right away by a medical professional. In fact, it is always a good idea to call your doctor if you notice anything other than minor pimple pus on your body, just to be safe.

Pus that has a blue, brown, or green color is not normal and requires immediate medical attention. These colors often signify the presence of dangerous bacteria, infections, or parasites and should be evaluated as soon as possible. Infections and pus buildup can lead to sepsis, which can be fatal when left untreated. Fortunately, most of these issues are treatable when caught early enough.

Clear Pus VS White Pus

You may notice a clear fluid that drains from pimples, minor injuries, or wounds from time to time. While many people assume this is a type of pus, it is actually known as serous fluid and it's a good sign in many situations. This type of drainage occurs when the area is still very inflamed, but infection is not currently present. As long as the drainage is not profuse and stays clear or slightly tinged with blood, there is no cause for concern. It should also improve over time.

Fluid that has built up an accumulation of dead white blood cells, along with bacteria and damaged tissues, will turn white. This is technically pus and only occurs when an infection is present. However, you may notice both pus and serous fluid in some situations. Keep in mind that while some serous fluid exiting through the skin is normal, a buildup of this substance is not. This leads to swelling and can be a sign of serious conditions that require prompt medical treatment.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon951621 — On May 16, 2014

I have a yellowish pus type pimple at the corner of my eyelid, and it is more irritated sometimes than at others, and I have had this condition for five years. The size has not increased, so which physician should I see, a dermatologist or eye specialist? What are the treatment options?

By anon354672 — On Nov 10, 2013

I had a pimple on my chest and it was the first one I ever had. I popped it and at first there was a green chunk of something then the pus came out. It was white but then a few more little green chunks came out. I don't know what that means.

By lighth0se33 — On Feb 12, 2012

My husband got swimmer's ear last summer, and though the pus that drained out was mostly yellow, it did have a bit of a blue tint to it. It was kind of strange to see this coming out of his ear.

His most intense symptom was the pain. His ear ached no matter what he did, and the canal was quickly swelling shut. He had to go to a doctor for relief.

She gave him some strong antibiotic ear drops. I had to pull his ear lobe down and back to open up the canal before dropping in the medicine.

The pus went away before the pain did, but he eventually got better. I had never seen blue pus before, and it did alarm me. I'm glad he got treated for it quickly.

By Perdido — On Feb 12, 2012

I got an eye infection as a child, and green pus collected at the corner of my eye. That wouldn't have been so alarming by itself, but what really bothered me was when I would wake up with my eyelids stuck together.

Pus had been oozing out during the night, gluing my lashes shut. I was very scared when I could not open my eyes the next day.

My mother soaked my eyelids with a damp, warm cloth, and the glue loosened up. I had a lot of dried pus that had crusted on my lashes, and there was plenty of it in the corner, as well. My doctor gave me medicated eyedrops, and I got better quickly.

By wavy58 — On Feb 11, 2012

@Oceana – I get pimples on my scalp that contain a lot of white pus, and just like facial acne, it turns to pinkish goo at the end. These scalp pimples are particularly painful to pop, because they tend to go deep.

I have to position my fingers about half an inch from the center of the bump before I squeeze. This way, I can reach down to the source of the pus and send it shooting forth like toothpaste from a tube.

I am always amazed at how much comes out. Sometimes, it shoots out so quickly that it hits the mirror. It looks like a little white blob, and a bit of liquid surrounds it, and it resembles salad dressing that has separated.

Even though the bumps are painful and tender to the touch, I know that the are not dangerous, since the pus is white. It's nice to have a color guide to follow regarding pus and its degree of danger.

By Oceana — On Feb 10, 2012

I have noticed that small pimples tend to contain white pus, while the ones that run deeper and get larger contain yellow pus that resemble the creamy color of mayonnaise. I do pop them, even though I've heard that this is unwise. I just can't leave something that disgusting to fester on my face.

I've also observed that though the first pus that comes out is cream-colored, the pus behind it is pink and mixed with clear fluid. When this starts to come out, I know that it is time to quit squeezing, because blood will follow.

Sometimes, even after I think I've gotten all the pus out, it will reform the next day. Then, I squeeze the rest of it out. Once it is all gone, a small scab usually forms as the spot heals.

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