Staph is short for Staphylococcus aureus, a type of bacteria that lives harmlessly on the skin and inside the nose of roughly 30% of people at any given time. Most of the time it causes no problems at all, but when it gets through a cut, scrape, or other break in the skin, it can cause infections ranging from minor skin bumps to serious illness.
Where Staph Lives on Your Body
Staph bacteria are incredibly common. About 20% of people carry them in their nose persistently, another 60% carry them on and off, and only about 20% of people rarely have them at all. The inside of the nose is the most well-known spot, but staph also colonizes the skin, especially in warm, moist areas like the armpits and groin. Carrying staph doesn’t mean you’re sick or dirty. It simply means the bacteria are present without causing harm, a state doctors call colonization.
The trouble starts when staph finds a way past your skin barrier. A small cut, a surgical wound, a hair follicle irritated by shaving, or even a crack in dry skin can be enough. Once inside, the bacteria multiply and produce a range of toxins and enzymes that damage surrounding tissue. Some of these toxins break apart skin cells, some punch holes in blood cells, and others disable the immune cells your body sends to fight back. This is why staph infections can escalate quickly and why even a small wound deserves basic cleaning.
Common Staph Skin Infections
Most staph infections stay on or just below the skin. The specific type depends on where and how deeply the bacteria take hold.
- Folliculitis: Pus-filled bumps that form around hair follicles and look like pimples. Unlike regular acne, these tend to be itchy and can develop into crusty sores.
- Boils (furuncles): Deep pockets of pus that commonly appear under the arms, around the groin, or on the buttocks. A cluster of connected boils on the neck is called a carbuncle.
- Impetigo: Sores, usually on the face, that burst open and leave behind a yellow-brown crust. This is especially common in young children.
- Cellulitis: A deeper skin infection where the affected area becomes swollen, warm, painful, and discolored, appearing red, purple, or brown depending on skin tone.
In some cases, the skin forms a blister that breaks open and leaves a raw, burn-like surface. This happens because certain staph toxins specifically target the protein that holds skin cells together, causing layers of skin to separate and peel.
When Staph Spreads Deeper
If staph bacteria reach the bloodstream, the infection becomes invasive and significantly more dangerous. This can happen through an untreated skin infection, a surgical site, or a medical device like a catheter or IV line. Once in the blood, staph can travel to virtually any organ.
The most serious complications include:
- Sepsis: The body’s immune response to the infection becomes so intense that it starts damaging its own tissues and organs.
- Endocarditis: Infection of the heart valves, which can permanently damage them.
- Osteomyelitis: Bone infection, most commonly affecting the knee, hip, or ankle.
- Septic arthritis: Infection inside a joint, such as the knee, shoulder, or hip.
- Pneumonia: Staph infection in the lungs, which can be severe and fast-moving.
- Toxic shock syndrome: A rare but life-threatening condition where staph toxins flood the bloodstream and damage multiple organs.
Invasive staph infections require hospital treatment and are diagnosed by finding the bacteria in blood, pus, tissue samples, or other body fluids. Imaging tests like MRIs, CT scans, or echocardiograms help doctors identify where the infection has spread.
Who Is Most at Risk
Anyone can get a staph infection, but certain situations raise the odds considerably. People who have recently had surgery or who have medical devices inserted into their body (catheters, prosthetic joints, pacemakers) face higher risk because these create direct pathways for bacteria to enter. Injection drug use is another major risk factor, since shared or unsterile needles introduce bacteria straight into the bloodstream.
Staph also spreads easily in close-contact settings. Athletes who share equipment or towels, people living in crowded housing, and healthcare workers who regularly touch patients are all more exposed. The bacteria pass from person to person through direct skin contact and through contaminated surfaces like doorknobs, gym equipment, and shared personal items.
MRSA and Antibiotic Resistance
One of the biggest concerns with staph is its ability to develop resistance to antibiotics. MRSA, or methicillin-resistant Staphylococcus aureus, is a strain that no longer responds to several common antibiotics. Globally, about 27% of staph bloodstream infections are caused by MRSA, according to 2023 surveillance data from the World Health Organization. In some regions, like the Eastern Mediterranean, that figure reaches 50%.
The good news is that MRSA rates are stable or declining in several parts of the world, including Europe and the Western Pacific. Standard staph infections that are not resistant (called MSSA) respond well to common oral antibiotics. MRSA infections require different medications, but they are still treatable. The key is identifying the type of staph involved, which is why doctors often take a culture from the infected area before choosing an antibiotic.
How Staph Infections Are Treated
For minor skin infections like small boils or folliculitis, treatment is often straightforward. A doctor may drain the pus and prescribe a short course of oral antibiotics. Many superficial infections improve within a week or two with proper care. Keeping the area clean, covered, and dry helps prevent the bacteria from spreading to other parts of your body or to other people.
Invasive infections are a different situation entirely. When staph reaches the bloodstream, bones, or heart, treatment typically involves intravenous antibiotics given in a hospital, sometimes for weeks. The specific drug and duration depend on whether the strain is resistant and which organs are affected. Blood cultures are repeated during treatment to confirm the bacteria are being cleared.
Preventing Staph Infections
Because staph bacteria are so common, prevention focuses on keeping them from entering the body rather than avoiding them entirely. Washing your hands regularly, cleaning cuts and scrapes promptly, and keeping wounds covered with a bandage until they heal are the most effective steps. Avoid sharing personal items like razors, towels, and washcloths, especially in locker rooms or shared living spaces.
If you notice a skin wound that becomes increasingly red, swollen, warm, or painful, or if pus develops, those are signs the infection may need treatment beyond home care. Staph infections that are caught early at the skin level are far simpler to treat than those that have had time to spread.