Pus is a thick fluid containing dead tissue, cells, and bacteria. Your body often produces it when it’s fighting off an infection, especially infections caused by bacteria.
Depending on the location and type of infection, pus can be many colors, including white, yellow, green, and brown. While it sometimes has a foul smell, it can also be odorless.
Keep reading to learn more about what causes pus and when you should call your doctor.
Pus-causing infections can happen when bacteria or fungi enter your body through:
- broken skin
- inhaled droplets from a cough or sneeze
- poor hygiene
When the body detects an infection, it sends neutrophils, a type of white blood cell, to destroy the fungi or bacteria. During this process, some of the neutrophils and tissue surrounding the infected area will die. Pus is an accumulation of this dead material.
Many types of infection can cause pus. Infections involving the bacteria Staphylococcus aureus or Streptococcus pyogenes are especially prone to pus. Both of these bacteria release toxins that damage tissue, creating pus.
Pus generally forms in an abscess. This is a cavity or space created by the breakdown of tissue. Abscesses can form on your skin’s surface or inside your body. However, some parts of your body are exposed to more bacteria. This makes them more vulnerable to infection.
These areas include:
- The urinary tract. Most urinary tract infections (UTIs) are caused by Escherichia coli, a type of bacteria that’s found in your colon. You can easily introduce it into your urinary tract by wiping from back to front after a bowel movement. It’s pus that makes your urine cloudy when you have a UTI.
- The mouth. Your mouth is warm and moist, making it the perfect environment for bacterial growth. If you have an untreated cavity or crack in your tooth, for example, you might develop a dental abscess near the root of the tooth or your gums. Bacterial infections in your mouth can also cause pus to collect on your tonsils. This causes tonsillitis.
- The skin. Skin abscesses often form due to a boil, or an infected hair follicle. Severe acne — which is a buildup of dead skin, dried oil, and bacteria — can also result in pus-filled abscesses. Open wounds are also vulnerable to pus-producing infections.
- The eyes. Pus often accompanies eye infections, such as pink eye. Other eye issues, such as a blocked tear duct or embedded dirt or grit, can also produce pus in your eye.
If you have an infection that’s causing pus, you’ll probably also have some other symptoms. If the infection is on the surface of your skin, you might notice warm, red skin around the abscess, in addition to streaks of red surrounding the abscess. The area might also be painful and swollen.
Internal abscesses usually don’t have many visible symptoms, but you might have flu-like symptoms. These can include:
These flu-like symptoms can also accompany a more severe skin infection.
Any cuts or incisions made during surgery can develop a type of infection called a surgical site infection (SSI). According to Johns Hopkins Medicine, people undergoing surgery have a 1-3 percent chance of getting one.
While SSIs can affect anyone who’s had surgery, there are certain things that can increase your risk. SSI risk factors include:
- having diabetes
- surgical procedures that last for more than two hours
- having a condition that weakens your immune system
- undergoing treatment, such as chemotherapy, that weakens your immune system
There are several ways that an SSI can develop. For example, bacteria might be introduced through a contaminated surgical instrument or even droplets in the air. Other times, you might already have bacteria present on your skin before surgery.
Depending on their location, there are three main categories of SSIs:
- Superficial. This refers to SSIs that only occur on your skin’s surface.
- Deep incisional. This type of SSI occurs in the tissue or muscle surrounding the incision site.
- Organ space. These occur within the organ being operated on or in the space surrounding it.
Symptoms of SSIs include:
- redness around the surgical site
- warmth around the surgical site
- pus draining from the wound or through a drainage tube if you have one
Treating pus depends on how serious the infection causing it is. For small abscesses on your skin’s surface, applying a wet, warm compress can help drain pus. Apply the compress a few times a day for several minutes.
Just make sure you avoid the urge to squeeze the abscess. While it might feel like you’re getting rid of the pus, you’re likely pushing some of it deeper into your skin. It also creates a new open wound. This could develop into another infection.
For abscesses that are deeper, bigger, or harder to reach, you’ll need medical help. A doctor can draw out the pus with a needle or make a small incision to allow the abscess to drain. If the abscess is very large, they may insert a drainage tube or pack it with medicated gauze.
For deeper infections or ones that won’t heal, you may need antibiotics.
While some infections are unavoidable, reduce your risk by doing the following:
- Keep cuts and wounds clean and dry.
- Don’t share razors.
- Don’t pick at pimples or scabs.
If you already have an abscess, here’s how to avoid spreading your infection:
- Don’t share towels or bedding.
- Wash your hands after touching your abscess.
- Avoiding communal swimming pools.
- Avoid shared gym equipment that would come in contact with your abscess.
Pus is a common and normal byproduct of your body’s natural response to infections. Minor infections, especially on the surface of your skin, usually heal on their own without treatment. More serious infections usually need medical treatment, such as a drainage tube or antibiotics. Contact your doctor for any abscess that doesn’t seem to be getting better after a few days.