What Is a Staph Infection?
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 shows that staph is the most common invasive bacteria in the United States.
Most people come into contact with staph bacteria frequently, either through the air or by touching other people, touching contaminated surfaces, or eating food contaminated with staph. Usually, staph is harmless. If too much of it builds up on your skin or enters your body, however, it can multiply and cause infections.
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Many of staph infections are mild, but some forms 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 notes that anyone can develop a staph infection. But some groups of people are more at risk. They include people with:
- Weakened immune systems
- Heart disease
- Cancer
- Type 1 or type 2 diabetes
- Eczema
- Lung disease
People in healthcare settings are also at higher risk for staph infections, as the 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. It 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.
A course of antibiotics can treat most staph infections. 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 an effective treatment, no longer works. MRSA is common in hospitals and nursing homes or long-term care facilities. It also spreads 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.
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.
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 shows 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. It occurs when staph infects your 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. It 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 indicates 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 wash your hands after touching surfaces in hospitals or clinics that you visit. If you have a staph infection, wash your hands often and avoid 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.
Updated:  
June 27, 2023
Reviewed By:  
Christopher Nystuen, MD, MBA