What Is Pus?

Pus is a thick fluid produced as part of the body's response to an infection. Pus is typically an opaque white-yellow color, but it can also be tinted brown or even green. It's usually odorless, though it may sometimes smell foul.

Pus is made up of a buildup of:

• Degenerating white blood cells
• Dead/living bacteria, as well as other microorganisms
• Tissue debris
  

A small amount of pus, such as from pimples, typically isn't a cause for alarm. But pus at the site of a wound, surgical incision, or deep interior location may require medical intervention.

This article discusses what causes pus, as well as what to do if you notice it.

Function

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

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.

Pus is often part of an abscess, which is a collection of pus in a cavity formed from the breakdown of infected tissues.

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.

Types

Pus can be visible on the surface of the skin. It may also form internally as a complication of an infection or injury.

Skin Infection

Types of skin conditions characterized by pus on or just beneath the skin's surface 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 may be accompanied by pain or swelling.

Internal Infection

Pus-filled abscesses can form internally, such as in the mouth or alongside internal organs. It 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 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: A collection of pus in the space between the lungs and the chest wall that 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

Causes

Punctures, scrapes, scratches, or other openings in the skin can allow bacteria that live on the skin to enter the body and cause an infection. This includes surgical incisions. There can also be deep internal infections with pus that occur after surgery, injuries, or illnesses.

Certain factors and underlying conditions can put you at risk for infections and wound complications with pus. They include:

• Poor hygiene, such as not washing your hands before touching a wound
• Diabetes
• Older age
• Smoking
• Severe obesity
• An immune system disorder, HIV infection, or cancer
• Medications that reduce immune system activity, such as corticosteroids or immunosuppressants
• Paralysis or limited mobility
• Low body temperature
• Long operations and hospitalization
• Emergency procedures

For people who have weak immune systems, pus may never form in an infected area. But most people with an infected cut or wound will experience:

• Redness
• Pain or tenderness
• Swelling
• Fever

Treatment

Treatments for infections with pus may include:

• Antibiotic medications
• Drainage procedures
  
• Surgical removal of infected tissues

Antibiotics

Most SSIs and skin wounds are treated with oral antibiotics or ointments.

Antibiotics are important because they help the body 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 case.

For post-surgery pus, your healthcare provider may recommend a special incision care program. They may want to see your incision in order to make sure there isn’t an underlying problem.

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.

Prevention

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.

Keep the 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.

When to Call Your Healthcare Provider

Some symptoms are a sign of infection. Always contact your healthcare provider if:

• You see pus, especially after physical trauma or surgery
• You have any redness or pain with a wound

Do not ignore a surgical incision with pus. But many types of drainage are normal. Clear fluid or blood-tinged fluid that is largely clear is considered normal unless there is a large quantity coming from the wound.

If you have any cloudy or white-yellow drainage, your healthcare provider should promptly examine it. Ignoring an infection can lead to:

• Serious problems
• A longer recovery
• More scarring

Don't delay seeing your healthcare provider or surgeon.

If you have a wound or surgical incision and experience any flu-like symptoms, even without pus, seek urgent medical care. Untreated infections can put you at risk of serious or even life-threatening conditions, such as sepsis.

Summary

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.

Making sure you avoid touching cuts and wounds with dirty hands can help prevent infection. Following your surgeon's orders after surgery can also help you prevent infection and the development of pus.

A Word From Verywell

One of the most important things you can do to avoid an infection with pus is to wash your hands often. This is crucial before and after caring for skin bumps, an incision, or wounds.

If it is too late to prevent an infection, plan to take the time needed to clean the affected area properly. Check the wound regularly for any signs of infection, and be sure to protect it when necessary.