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Your skin is your body's largest organ. It has many different functions, including covering and protecting your body. It helps keep germs out. But sometimes the germs can cause a skin infection. It often happens when the germs enter your body through a break, cut, or wound on your skin. Other skin infections can happen in places where the skin rubs together, especially if the area is moist. Infections can also happen when you have a poor blood supply to an area of your body or if your immune system is weakened because of another disease or a medical treatment.

Some skin infections cover a small area on the top of your skin. Other infections can go deep into your skin or spread to a larger area.

Skin infections are caused by different kinds of germs. For example,:

• Bacteria cause cellulitis, impetigo, and staphylococcal (staph) infections
• Viruses cause shingles, warts, and herpes simplex
• Fungi cause athlete's foot and yeast infections
• Parasites cause body lice, head lice, and scabies

You are more likely to get a skin infection if you:

• Have poor circulation
• Have diabetes
• Are older
• Have an immune system disease, such as HIV
• Have a weakened immune system because of chemotherapy or other medicines that suppress your immune system
• Have to stay in one position for a long time, such as if you are sick and have to stay in bed for a long time or you are paralyzed
• Are malnourished
• Have excessive skinfolds, which can happen if you have obesity

The symptoms depend on the type of infection. Some symptoms that are common to many skin infections include rashes, swelling, redness, pain, pus, and itching.

To diagnose a skin infection, your health care provider will do a physical exam and ask about your symptoms. You may have lab tests, such as a skin culture. This is a test to identify what type of infection you have, using a sample from your skin. Your provider may take the sample by swabbing or scraping your skin or removing a small piece of skin (biopsy). Sometimes providers use other tests, such as blood tests.

The treatment depends on the type of infection and how serious it is. Some infections will go away on their own. When you do need treatment, it may include a cream or lotion to put on the skin. Other possible treatments include medicines and a procedure to drain pus.

Staphylococcus (staph) is a group of bacteria. There are more than 30 types. A type called Staphylococcus aureus causes most infections.

Staph bacteria can cause many different types of infections, including:

• Skin infections, which are the most common types of staph infections.
• Bacteremia, an infection of the bloodstream. This can lead to sepsis, a very serious immune response to infection.
• Bone infections.
• Endocarditis, an infection of the inner lining of the heart chambers and valves.
• Food poisoning.
• Pneumonia.
• Toxic shock syndrome (TSS), a life-threatening condition caused by toxins from certain types of bacteria.

Some people carry staph bacteria on their skin or in their noses, but they do not get an infection. But if they get a cut or wound, the bacteria can enter the body and cause an infection.

Staph bacteria can spread from person to person. They can also spread on objects, such as towels, clothing, door handles, athletic equipment, and remotes. If you have staph and do not handle food properly when you are preparing it, you can also spread staph to others.

Anyone can develop a staph infection, but certain people are more likely to get one, including those who:

• Have a chronic condition such as diabetes, cancer, vascular disease, eczema, and lung disease
• Have a weakened immune system, such as from HIV, medicines to prevent organ rejection, or chemotherapy
• Had surgery
• Are in the hospital
• Use a catheter, breathing tube, or feeding tube
• Have an implanted device, such as a pacemaker or artificial joint or heart valve
• Have burns, especially if they are deep or cover a large area of the body
• Are on dialysis
• Inject illegal drugs
• Do contact sports, since you may have skin-to-skin contact with others or share equipment

The symptoms of a staph infection depend on the type of infection:

• Skin infections can look like pimples or boils. They may be red, swollen, and painful. Sometimes there is pus or other drainage. They can turn into impetigo, which turns into a crust on the skin, or cellulitis, a swollen, red area of skin that feels hot.
• Bone infections can cause pain, swelling, warmth, and redness in the infected area. You may also have chills and a fever.
• Endocarditis causes some flu-like symptoms: fever, chills, and fatigue. It also causes symptoms such as rapid heartbeat, shortness of breath, and fluid buildup in your arms or legs.
• Food poisoning typically causes nausea and vomiting, diarrhea, and fever. If you lose too many fluids, you may also become dehydrated.
• Pneumonia symptoms include a high fever, chills, and cough that doesn't get better. You may also have chest pain and shortness of breath.
• Toxic shock syndrome (TSS) causes high fever, sudden low blood pressure, vomiting, diarrhea, and confusion. You may have a sunburn-like rash somewhere on your body. TSS can lead to organ failure.

Your health care provider will do a physical exam and ask about your symptoms. Often, providers can tell if you have a staph skin infection by looking at it. To check for other types of staph infections, providers may do a culture, with a skin scraping, tissue sample, stool sample, or throat or nasal swabs. There may be other tests, such as imaging tests, depending on the type of infection.

Treatment for staph infections is antibiotics. Depending on the type of infection, the antibiotics might be a cream, ointment, medicines (to swallow), or intravenous (IV) medicine. If you have an infected wound, your provider might drain it. Sometimes you may need surgery for bone infections.

Some staph infections, such as MRSA (methicillin-resistant Staphylococcus aureus), are resistant to many antibiotics. There are still certain antibiotics that can treat these infections.

Certain steps can help to prevent staph infections:

• Use good hygiene, including washing your hands often.
• Don't share towels, sheets, or clothing with someone who has a staph infection.
• It's best not to share athletic equipment. If you do need to share, make sure that it is properly cleaned and dried before you use it.
• Practice food safety, including not preparing food for others when you have a staph infection.
• If you have a cut or wound, keep it covered.