Impetigo is an infection of the outer layer of the skin (epidermis). It's most often caused by certain bacteria on the skin. Impetigo is most common in children ages 2 to 5 years. But older children and adults can get it, too. It's more common in the summer months.

Normally, your skin is covered by millions of bacteria. Many of these are harmless, and some may be good for you. But sometimes harmful bacteria can grow on your skin. If they get through the outer layer of your skin, they may start to grow more. This can cause impetigo.

There are three kinds of impetigo:

• Nonbullous impetigo. This is the most common form in adults. It causes thick, honey-colored crusts.
• Bullous impetigo. This causes large blisters on the skin.
• Ecthyma. This is a more serious form that often results from untreated impetigo. It causes ulcerative sores that go down into the deeper layers of the skin.

Impetigo is caused by bacteria. The most common is Staphylococcus aureus, also called staph. Streptococcal bacteria, also called strep, can cause it, too. Some impetigo is caused by a type of bacteria called MRSA (methicillin-resistant Staphylococcus aureus). MRSA is hard to kill. Impetigo caused by this bacteria can be hard to treat.

Many people have these kinds of bacteria on their body from time to time. A smaller number of people have lifelong (permanent) colonies of these potentially harmful bacteria on their skin. This is known as being "colonized" with the bacteria. The bacteria may grow inside your nose, armpit, throat, genitals, hands, or some other area without causing symptoms. When they're just on top of the skin, they often don't cause problems. But a small break in the skin allows the bacteria to cause an infection.

People who have these bacteria on their skin are more likely to get impetigo. You may also get impetigo if you have a cut that has been in contact with someone colonized with the bacteria.

These risks are higher in people with:

• Atopic dermatitis or eczema.
• Diabetes.
• Liver problems.
• HIV/AIDS infection.
• Dialysis treatment.
• I.V. (intravenous) drug use.
• Skin sores, such as from scabies.
• Immune deficiencies.

You may also have an higher risk if you live or work in a place where people are in close contact. This includes dorms, barracks, or prisons. Having a family member with it may also increase your risk. Not washing your hands after touching someone with impetigo greatly increases your risk of getting the infection.

Impetigo causes red bumps to form on your skin, often on your face, arms, or legs. The bumps then become blisters. The blisters burst and scab over, forming a yellow-brown crust. The skin may also look reddish or raw where the blisters popped open. The rash often starts in a single spot, but scratching may spread it to other areas of the body. The rash may be slightly painful to the touch, and it may also itch.

If you have the bullous type of impetigo, you may have larger blisters filled with a clear fluid. If you have ecthyma, you may have deeper sores with a yellow crust and purple borders.

You may be diagnosed by your doctor or a dermatologist. A dermatologist is a doctor who specializes in skin diseases.

Your doctor will ask about your health history, symptoms, and if you've been in contact with anyone that has impetigo.

You'll also have a physical exam, including a close exam of your skin. Your doctor will need to make sure your symptoms aren't caused by other skin problems that have similar symptoms. They may take a sample of pus from one of your blisters to check for bacteria.

Antibiotics are the main treatment for impetigo. If you have only a few affected spots that don't go deeply into your skin, you may be given an antibiotic cream or ointment. You apply it to the affected areas of your skin.

If you have a more severe infection, you'll likely need to take an antibiotic by mouth. Your doctor will choose an antibiotic based on the type of bacteria that caused your impetigo. Take your antibiotics as directed. Do not stop taking them just because you feel better. You need to take the full course of antibiotics.

Your doctor may also give you instructions about cleaning the affected areas with soap and water several times a day. You'll also need to wash your hands often. This is to help prevent spreading the infection to others. You may also need to cover the affected areas. This can help prevent spreading it to other parts of your body and to other people.

Often the infection will go away in a week or so with the correct treatment. Only rarely does the infection leave scars. Getting treatment quickly also reduces the chances of serious problems.

If you get repeated bouts of impetigo, your doctor may need to check you for a skin problem that makes it hard for you to fully fight the infection.

Untreated impetigo can lead to deeper infection, especially if it's caused by staph bacteria. Possible complications include:

• Deeper infection of your skin (cellulitis).
• Infection of the lymphatic system (lymphangitis).
• Bacteria in the blood (bacteremia).

These may need more antibiotic treatment and other types of medical support.

Rare complications include:

• Glomerulonephritis. This is inflammation in the filtering part of your kidney. It may happen after some kinds of Streptococcal infections. It may cause only minor problems. But it can cause sudden temporary kidney failure.
• Rheumatic fever. This can also be caused by a Streptococcal impetigo infection. This disease may affect the heart, joints, skin, and brain.

Impetigo often spreads through direct skin-to-skin contact. You may be able to prevent it by taking certain steps. For example:

• Always wash with soap and water right after you touch someone with the infection.
• Don't share personal items, such as towels or combs.
• Wash towels and bed linens in hot water.
• Wash your hands after handling tissues that could contain germs.
• Sneeze into a tissue or the crook of your arm, not into your hands, to help prevent spreading germs.

Contact your doctor if your infection is not clearing up within a week of starting your treatment, or if it seems to be getting worse.

• Impetigo is an infection of the outer layer of your skin. It's often caused by the bacteria staph or strep that invades injured skin. The rash may blister and appear red or yellow and crusty.
• You may have a greater risk of impetigo if you are colonized by certain bacteria, or if you have certain health conditions.
• Antibiotics are the main treatment for impetigo. You may need to apply a cream to your skin. Or you may need to take an antibiotic by mouth.
• Untreated impetigo can cause serious complications, such as deeper infection. Getting treatment quickly can help reduce the risk of more problems.
• Handwashing and other steps may help prevent getting or spreading impetigo.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are and when they should be reported.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours or on weekends.