What is pus?

When this thick fluid shows up, it’s time to address an infection—in these ways

By Jennifer Larson | Apr. 28, 2022 Medically reviewed by Chad Shaffer, MD

It’s never a good thing when you see pus oozing out of some part of your body. In medical terms, the drainage from a wound or infected area of the body is sometimes called purulent exudate or liquor puris. But most of us know the goopy fluid that comes from an abscess, a pustule, a carbuncle, a wound, or even a surgical incision simply as pus.

What is pus?

When your immune system detects an invader, like a harmful form of bacteria, it activates an immune response of white blood cells called leukocytes to defend your body. The result is often pus. What is pus made of? White blood cells, along with some of the dead bacteria they were battling.

Pus is often a pale color, whitish-yellow, but it can be pink, red, brown or even take on a green tinge. You might get a whiff of a foul-smelling odor, too.

What causes pus?

It’s gross, yes. But pus exists for a reason. Your body produces pus when it’s fighting an infection. Infections can occur when microorganisms such as bacteria or fungi enter a cut, incision, or puncture. Or, they can occur if you inhale infected respiratory droplets from another person.

The symptoms of infection can vary, depending on the type of microorganism, as well as the location of the infection. “Pus usually accompanies one of the four signs of infection: heat, swelling, pain and redness,” says Brian M. Derby, MD, a plastic surgeon with Sarasota Plastic Surgery Center in Sarasota, Florida.

Certain health conditions increase your risk for infection such as diabetes or immune system disorders. “Some people do seem predisposed to skin infections,” adds Mary Alice Mina, MD, a dermatologist and dermatologic surgeon at Baucom & Mina Derm Surgery in Atlanta, Georgia. “Oftentimes, these patients are colonized with staphylococcus aureus in their nostrils. When patients have a history of skin infections, we will also swab or treat the inside of their nostrils with medication to decrease bacteria there.”

Lifestyle factors can raise your risk for developing an infection, too. For example, research suggests that people who smoke are more likely to develop peritonsillar abscesses, which are sores filled with pus at the back of the throat.

Is pus a good thing?

“Nope,” says Dr. Derby. “P-U-S is B-A-D.” It’s the byproduct of your body fighting an infection. It’s most noticeable in wounds on your skin, but it can occur in abscesses anywhere in your body. It’s a sign that you need some sort of treatment, whether that’s cleaning and draining the infected wound, applying antifungals for fungal infections, or antibiotics depending on the location and severity of infection.

Locations

Pus can develop on many parts of the body, unfortunately, when the conditions are right (or wrong, such as the case may be). Here are some examples of the many infection types that can lead to pus formation:

Urine: You may not be familiar with the term pyuria, but you may have noticed a telltale sign. Your urine may look a little cloudy if it contains some white blood cells, usually as a sign of a kidney infection or urinary tract infection.
Throat: You might develop a thick pocket of pus at the back of your throat known as a tonsillar abscess as the result of a bacterial infection like tonsillitis, mononucleosis, or even tooth or gum infections.
Gums: You can also develop a pocket of pus on your gums, usually as the result of infection or poor oral hygiene.
Stool: Your stools can contain pus or mucus, but you may not realize it. But a stool sample or stool culture may reveal this particular sign of infection.
Eyes: If you notice a yellowish discharge coming out of your eye, it could be a sign of an infection called bacterial conjunctivitis, also known as pink eye.
Ears: If your child has pus or cloudy fluid coming out of an ear, it’s likely a sign of an ear infection or possibly a ruptured eardrum. Call your child’s pediatrician, especially if your child also has some hearing loss or intense pain.
Belly button: Bacteria love to lurk in the dark recesses of your navel, so if you notice some pus draining out of your belly button, it could be the result of a bacterial infection. If you’ve recently undergone abdominal surgery, it could also be a sign of post-surgical infection.
Lungs: An infection in the cavity between your lung and the pleural space around it can lead to the development of a pus-filled cavity called empyema. It can put pressure on your lungs, making it hard to breathe.
Fingers: A staph infection that develops in a hair follicle or oil gland in your finger or in the nail bed area can lead to a red, swollen, pus-filled digit.
Wounds: It’s all too easy for bacteria to flourish in a wound or cut on the skin, causing an infection that weeps fluid or seeps pus. Infections can even develop in surgical site wounds, with the most common ones caused by the bacteria Staphylococcus, Streptococcus, and Pseudomonas, according to Johns Hopkins Medicine.
Nose: If you sustain a blow to your nose, watch out because it’s possible that an abscess may form. Nasal abscesses full of pus also sometimes develop as a result of sinus infections.
Nails: Bacteria can work their way through cuts into your cuticle or other parts of your nail and cause infections known as paronychia. As a result, you may notice inflammation or a collection of pus under your skin.
Pimples: A lot of unhappy teenagers can tell you how unpleasant it is to live with pus-filled acne cysts that develop deep under the skin. Cystic acne can be both unsightly and painful.
Piercings: Any type of bacteria that work their way down into a new piercing can cause a painful infection that may ooze pus.
Bikini line and armpits: Razors can eliminate unwanted hair, but they can also lead to ingrown hairs, which can cause red bumps filled with pus to develop.

Colors

The color of the pus that you’re noticing is usually the result of a build-up of dead neutrophils, a type of white blood cell.

Pus color chart
Pus color	Pus color meaning
Green	Some white blood cells produce an antibacterial protein called myeloperoxidase that looks greenish in color and sometimes the bacteria Pseudomonas aeruginosa produces green pigments
Yellow	A nonspecific pus color which on a skin wound could indicate bacterial infection such as strep or staph
Red or pinkish	Some blood may have seeped into the area

Odors

Pus can smell pretty bad. The foul odor can be a sign of a particular type of infection. For example, infections caused by Pseudomonas aeruginosa, which are common healthcare-acquired infections, may be particularly noxious.

Pus treatments

If you notice pus, including pus that’s seeping out of a skin abscess, furuncle, wound, or other place on your skin, don’t ignore it. Your treatment will vary, depending on the location and the type of infection. Typically, though, it’s a two-pronged approach:

Draining the wound
Treating the infection with oral or topical antibiotics

Don’t try to drain pus on your own by picking or squeezing the area. That can force bacteria down into the damaged tissue and lead to scarring. Instead, apply a warm compress to the affected area several times per day to see if that gets the abscess to open up and drain on its own. “A thick ointment like petrolatum is also helpful in providing a moist wound bed, as well as protection from outside bacteria,” Dr. Mina says. However, it is typically better to let your healthcare provider examine your abscess and then drain the pus out safely.

Your provider can determine the source of the pus and even perform a wound culture to determine the best treatment and medical advice.

Prevention

Prevention is always the best cure. With that in mind, always keep an eye on any cuts or wounds on the skin’s surface throughout the healing process so you can watch for signs of a developing infection. After surgery, monitor the incision closely as it heals so you can act if necessary. “Most incision infections will develop at three to five days after an operation,” Dr. Derby says, “so keep close tabs on your progress during that period.”

“For a wound or incision to heal, it needs oxygen and nutrients from good blood flow, and proper cleaning to keep bacteria counts low on a wound or incision surface,” Dr. Derby says. Wash your hands thoroughly any time you have to touch a wound or opening so you don’t accidentally spread bacteria. Be sure to change bandages regularly.

You can also take lifestyle steps that protect you against infections, such as quitting smoking, eating a well-balanced diet, managing chronic conditions, and exercising.