What Is a Staph Infection?

By Katharine Paljug @kpaljug
September 25, 2017

Staph bacteria live on many people. But what is a staph infection? Learn the causes, how to prevent one, and what to do if you get one.

What is a staph infection?

The bacteria Staphylococcus aureus, or staph for short, is a common germ. About 30 percent of people have it living in their noses or on their skin. Research published in 2016 found that staph was the most common invasive bacteria in the United States.

Most people come into contact with staph bacteria frequently, either through the air, by touching other people, by touching contaminated surfaces, or by eating food contaminated with staph. Usually, staph is harmless. However, if too much of it builds up on your skin or enters your body, it can multiply and cause infections.


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Many of these infections are mild, but some forms of staph infection can be dangerous, especially if they are resistant to antibiotics. In some cases, untreated staph infections can become fatal.

Many staph infections appear similar to other conditions, so they can be diagnosed only in a laboratory. Because Staphylococcus aureus is a bacterium, infections often require antibiotic treatment.

The Centers for Disease Control and Prevention (CDC) notes that anyone can develop a staph infection. However, some groups are more at risk. This includes people with weakened immune systems and those with chronic diseases, such as heart disease, cancer, diabetes, eczema, and lung disease.

People in healthcare settings are also at higher risk for staph infections, as these bacteria can spread quickly through hospitals, clinics, and nursing homes. Staph infections are also common in crowded facilities such as schools, daycares, gyms, cruise ships, and military barracks.

Staph skin infections

Staph skin infections usually begin as red, swollen, irritated pockets of pus that look like pimples or boils. More severe skin infections include cellulitis and impetigo.

Cellulitis is a rash that can appear all over your skin. Symptoms include:

  • Expanding patches of skin that are red, hot, swollen, and painful
  • Nausea
  • Shivers and chills

Impetigo, or “school sores,” often spreads through schools and daycare centers. It appears as itchy sores or blisters around the mouth and nose, which develop a brown or yellow crust if they rupture.

Staph bacteria can also infect open wounds in your skin. If a wound becomes infected, it will heal more slowly. You may also notice:

  • Red, swollen, and tender areas
  • Pus discharge
  • An unpleasant odor

A dangerous type of staph skin infection is staphylococcal scalded skin syndrome, or SSSS. This occurs when staphylococcal bacteria release poison that begins to damage your skin, making it look as if you have been burned with boiling water. If you have SSSS, your skin will become painful to touch and may begin to peel off. You will also have a fever of 100.4° F or higher.

Most staph infections that affect the skin can be treated with a course of antibiotics that you take at home. Cellulitis and SSSS typically require hospitalization.

Methicillin-resistant Staphylococcus aureus (MRSA)

Another dangerous staph infection is called methicillin-resistant because the antibiotic, methicillin, which used to be effective treatment, no longer works. MRSA is common in hospitals and nursing homes or long-term care facilities. It is also spreading among healthy children and adults outside the healthcare system, such as in athletic facilities. A person may be a carrier. Or he or she may have the infection.

How do you get MRSA? People who are colonized (when you carry the bacteria but are healthy) have MRSA in their noses or on their skin. Even though they’re not sick, they can spread the germs to others. In hospitals, MRSa can spread from patient to patient on the hands of healthcare workers. It can also spread on objects, such as a cart or door handles. Outside hospitals, MRSA usually spreads through skin-to-skin contact, shared towels or athletic equipment, or through close contact with an infected person.

Learn more about MRSA here.

Staphylococcal food poisoning

The symptoms of food poisoning from staph bacteria are similar to other forms of food poisoning. You may experience:

  • Diarrhea
  • Nausea and vomiting
  • Dehydration
  • Stomach cramps or pain
  • Low blood pressure
  • Flu-like symptoms, including mild fever

If you develop a high fever or severe dehydration, you may need to seek medical attention. Otherwise, your symptoms will likely resolve on their own after a few days.

Invasive staph infections

Invasive staph infections can take many forms. One of the most common is pneumonia, which happens when bacteria settle in your lungs. Symptoms of pneumonia include difficulty breathing, coughing, and a fever over 100.4° F.

Staph bacteria can also settle in your joints, causing septic arthritis, or in your bones, causing osteomyelitis. Symptoms of both conditions include:

  • Red, swollen skin and severe pain at the site of the infection
  • Stiff or swollen joints
  • Nausea or dizziness
  • Confusion
  • Rapid heartbeat
  • Difficulty breathing

Toxic shock syndrome, or TSS, occurs when staph bacteria enter your bloodstream. It can happen to anyone, but research has found that it is often associated with using tampons improperly. Symptoms of TSS include fever, vomiting, and feelings of faintness.

Endocarditis, which affects the valves of the heart, is a potentially fatal infection. Symptoms of endocarditis include:

  • Fever, chills, and sweating
  • Muscle aches
  • Low blood pressure and dizziness
  • Shortness of breath
  • Coughing
  • Headache
  • Weakness or fatigue
  • Unexplained weight loss

The most dangerous type of staph infection is sepsis, or blood poisoning. This occurs when staph infects the blood. Sepsis is a medical emergency and requires immediate hospitalization. Symptoms of sepsis include:

  • Feeling generally unwell
  • Fever
  • Rapid heartbeat and breathing
  • Dizziness
  • Feeling confused or disoriented
  • Decreased urination

Any invasive staph infection can become life-threatening. They may need to be treated with antibiotics and require hospitalization. If you have symptoms of any of these conditions, seek medical help.

How to prevent a staph infection

Research has found that improved personal hygiene leads to lower rates of staph infections.

Always wash your hands before preparing food or eating, and after using the bathroom, holding pets, or interacting with a sick person. Wipe down equipment at the gym before you use it, and was your hands after touching surfaces in hospitals or clinics that you visit. If you have a staph infection, wash your hands often and avoiding touching the infected area.

Keep wounds clean, and do not touch your eyes, nose, or mouth with dirty hands.

Do not share personal items, food, or drinks with other people, especially if you know they have a staph infection. At home, keep surfaces clean, particularly in the kitchen and bathroom, and wash bedding, towels, and clothes frequently.




March 26, 2020

Reviewed By:  

Christopher Nystuen, MD, MBA