Pus and Its Possible Causes

What pus from a wound may be telling you and when to see a doctor

Pus is a thick fluid made up of degenerating white blood cell, dead/living microorganisms (like bacteria), and tissue debris. It is produced as part of the body's response to an infection.

Pus is typically a white-yellow color and opaque, rather than clear. It can also be tinted brown or even green. It's usually odorless, but a foul odor may sometimes be present.

Pus in a pimple, or a similar small amount elsewhere on the body, isn't typically cause for alarm. But pus at the site of a wound, a surgical incision, or deep inside the body may require medical intervention.

This article discusses what causes pus and why you may see it in various locations of the body. It discusses the diagnosis and treatment of conditions that cause pus, and when you may need to see a healthcare provider for it.

Pimple near the mouth

Photo: Angela Palmer


Why the Body Makes Pus

Pus itself doesn't actually serve a function. Rather, it is a product of your immune system's fight against an invader, such as a bacterium.

In medical settings, you may also hear it referred to as a purulent drainage. This describes a pus-like discharge associated with infection, often after surgery.

When your immune system detects something that shouldn't be there, it sends infection-fighting white blood cells called leukocytes to the area. They get to work killing and absorbing whatever has found its way in, as well as breaking down dead tissue.

During this process, the white blood cells also break down and die. All of this material mixes together, forming pus.

When the Body Makes Pus

Pus is often due to skin infections. Pus also may arise from an abscess, a pus-filled cavity formed from the breakdown of infected tissues.

However, pus may be produced due to an internal infection and never make it to the surface of your skin.

Skin Infections

Pus due to a skin infection is visible. It may be accompanied by redness, pain or tenderness, swelling (edema), or fever.

Specific types of skin conditions that can cause pus include:

  • Acne: Pores clogged with oil and debris form pimples or pustules on the skin's surface that contain pus.
  • Folliculitis: Small acne-like bumps form from infected hair follicles.
  • Boils or furuncles: Painful nodular bumps form from infected hair follicles that are typically caused by Staphylococcus aureus.
  • Carbuncles: A group of connected boils
  • Superficial surgical site infection (SSI): An SSI is at the skin level only. Pus can form along the incision, which may become red and painful when touched.
  • Trauma wounds: Pus and yellow crust at the site of a wound, caused by injury or physical trauma that also may be accompanied by pain or swelling.

Abscesses can happen just under the skin or anywhere in the body. They typically are the result of bacteria such as Streptococcus or Staphylococcus aureus gaining access to tissues, such as through a small opening in the skin. Fungus or parasites can also lead to abscesses.

Is It Good for Pus to Come Out?

It can be part of drainage necessary for healing, but it can also be cause for concern. Don't encourage pus to come out, however. Doing so can cause or worsen infection, and it may make the skin more tender or even painful.

Internal Infections

Pus-filled abscesses can form internally, such as in the mouth or alongside internal organs. This can be a result of a surgical complication, injury, or untreated bacterial or fungal infection.

There are many types of internal abscesses and conditions that can lead to pus, including:

  • Abscessed tooth: A dental infection in or near the root of a tooth
  • Deep surgical site infection (SSI): An infection can occur internally in muscles and other tissues, or may form in the organ or area of the surgery.
  • Peritonsillar abscess: Spots of pus at the back of the throat or behind the tonsils can form as a symptom of strep throat or tonsillitis.
  • Empyema: An empyema is a collection of pus in the space between the lungs and the chest wall. It can be a complication of bacterial pneumonia or lung surgery.
  • Brain abscess: A rare swelling of pus in the brain that can be caused by a bacterial or fungal infection
  • Septic arthritis: A serious joint infection that can form after bacteria travels through the bloodstream to the joint

A urinary tract infection (UTI) also can cause pus to build up in the urinary tract. Pus cells in urine, called pyuria, is a sign of UTI but may indicate a more serious problem.

When to See a Healthcare Provider

Let your healthcare provider know about any pus-like discharge. This is particularly important if you recently had surgery or have an abscess.

Seek urgent medical care if you have any of the following symptoms:

If you have a wound or surgical incision and experience any flu-like symptoms, even without pus, seek urgent medical care.

Ignoring an infection can lead to more scarring and a longer recovery. It can also put you at risk for serious and even life-threatening conditions, such as sepsis.

Wound Drainage After Surgery

Clear or blood-tinged fluid that is largely clear coming from a surgical wound is considered normal unless there is a large amount of it. If you have any cloudy or white-yellow drainage, however, your healthcare provider should promptly examine your incision.

Pus Treatment

Pus will usually be treated on the basis of its cause and a specific type of infection. These treatments and therapies may include:


Most SSIs and skin wounds are treated with oral antibiotics or ointments. Antibiotics are important because they help the body to heal faster. They may also keep an infection from becoming worse.

Your healthcare provider may collect your wound drainage and send it to a lab to determine what type of bacteria is causing the infection. This process is called a culture and sensitivity test.

Results can be used to determine which antibiotic may be most effective and efficient at clearing the infection in your specific case.

Drainage and Tissue Removal

In some cases, an abscess drainage procedure to remove pus or dead tissue may be needed to get rid of the infection.

Sepsis is a dangerous and life-threatening condition in which an infection enters the bloodstream. It can then spread throughout the body. If this occurs, you will need to be hospitalized.

Preventing Pus From Developing

There are simple things you can do to reduce your risk of developing an infection with pus:

  • Wash cuts and other wounds gently with soap and water.
  • Follow your healthcare provider's care instructions after surgery or hospitalization for injuries.
  • Wash your hands thoroughly and regularly.
  • Don't squeeze pus out of pimples or boils. Instead, gently apply a warm compress several times a day.
  • Don't share towels or razors.
  • Eat a healthy, balanced diet.
  • Be vigilant about controlling your blood sugar if you have diabetes.
  • Quit smoking.

Before and After Surgery

Between 1% and 3% of people who have surgeries develop an infection, according to the Centers for Disease Control and Prevention. There are steps you can take before and after any procedure to reduce your risk of an SSI.

Before Surgery
  • The night before surgery, wash your whole body with soap in the bath or shower.

  • Do not shave near the area where the surgery will be, since it can irritate the skin and make you more prone to infection. (Your healthcare provider may use electric clippers just before surgery to clear hair from the region.)

After Surgery
  • Family or friends should always wash their hands before visiting. They should not touch your wound unless they are the person caring for it.

  • Follow instructions for wound care after leaving the hospital.

  • Always wash your hands before and after caring for the wound.

  • Most surgical infections occur within a month. During this time, inspect your incision daily for signs of infection.

  • Do not scrub your incision. Slather it with antibiotic ointment, or clean it with alcohol or peroxide unless instructed otherwise by your healthcare provider.

Always keep the surgical incision dry and protect it with a clean bandage. In general, do what was recommended in your instructions for incision care after surgery unless you are told otherwise.

How to care for incisions with pus.

 Verywell / Laura Porter


Your body produces pus as a response to infection. It is made up of degenerating white blood cells, bacteria, and tissue debris.

Openings in the skin, such as cuts and wounds, allow bacteria to enter. When the bacteria enters, it can cause an infection. Make sure you avoid touching cuts, wounds, or surgical incisions with dirty hands.

Follow your surgeon's orders during recovery, which will help you to prevent infection and the development of pus. Check the wound regularly for any signs of infection, and be sure to protect it when necessary.

Frequently Asked Questions

  • What is the medical term for pus?

    Purulent exudate is the medical term for pus. It is sometimes called purulent drainage, and the fluid can be called liquor puris.

  • What do the different colors of pus mean?

    Pus is usually an opaque, white-yellow color. It can also be brown or green. Different colors of pus can hint at certain infections, but a formal diagnosis from a healthcare provider is still necessary to confirm the cause.

  • Should I drain pus out of an infected wound?

    No, you should not drain pus out of an infected wound yourself. Let a medical professional handle treatment. Follow their instructions for proper care.

  • How long does wound drainage last?

    Wound drainage can last anywhere from one to five weeks. This depends on the size and type of wound. If a surgical drain is required after surgery, your doctor will let you know how long they expect it to be in place.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.