What is Impetigo?
Impetigo is a common type of skin infection. Picking at sores or scratching itchy bites may allow the bacteria which cause impetigo to enter the skin.
- Bacteria may enter through a break in the skin. Typically the break in the skin is obvious (such as a skinned knee or a cut or even an insect bite), but even very small, microscopic breaks may allow for bacteria to enter.
- Once the bacteria get into the inner layers of the skin, they grow and multiply, creating a blister. Usually, this blister becomes filled with pus and then bursts, leaving a crust. It is this blistering and crusting which is typical of impetigo.
- There are two common forms of impetigo, referred to as bullous and nonbullous.
- Bullous impetigo is less common and is only caused by staphylococci. Typically this form results in the formation of larger blisters.
- Nonbullous impetigo is most common and is generally caused by a mild traumatic break in the skin and can be caused by two types of bacteria, streptococci or staphylococci. It results in the formation of smaller blisters.
As mentioned above, two main types of bacteria cause impetigo: Streptococcus and Staphylococcus organisms. Both are commonly found in the environment and on the surface of many people's skin. Group A Streptococcus is the most common cause of impetigo. This is the same organism that causes strep throat and can be spread directly from person to person or through contact with contaminated objects.
Impetigo Symptoms and Signs
Impetigo appears as a rash that may occur anywhere on the body and but commonly affects the face and other exposed areas.
- The rash may be blister-like, reddish, and have a honey-colored crust, or will have a combination of all three.
- The margins of the rash are usually fairly sharp.
- The rash is sometimes mildly painful and is itchy.
When to Seek Medical Care
Someone should call a doctor as soon as he or she notices a reddish, weeping, or blistery rash. Treating the rash with antibiotics will help the infection go away faster and also will prevent spread to others. The itching that often comes with the impetigo rash sometimes provides an added incentive to get the rash treated quickly. In some uncomplicated cases, over-the-counter topical antibiotics are effective in eradicating the infection.
Emergency treatment is rarely needed.
Doctors can usually distinguish an impetigo rash by looking at it. No lab tests are required. Occasionally rashes and blisters caused by toxins, such as poison ivy, or others might be confused with impetigo. A doctor will take a complete history to determine the appropriate diagnosis and treatment.
Self-Care at Home for Impetigo
- Clean all sores and bites with antibacterial soap and water. Don't scratch or pick.
- The infection is contagious. Use separate washcloths, razors, and hand towels.
- Often, the rash and infection will go away on its own, but antibiotics are usually needed to get rid of the infection.
- Apply antibacterial ointment, but wash hands well after applying it.
- If the sores are in areas that are shaved (men on their face; women on their legs), shave around the sores to avoid spreading the infection further.
The physician will typically prescribe oral or topical antibiotics or both.
- Topical: Topical antibiotic treatment is with a prescription-strength medication called mupirocin (Bactroban). Most nonprescription antibiotic ointments, such as Neosporin, are not effective. This is generally the first line of treatment for nonbullous impetigo, localized to a single area
- Oral: Usually oral antibiotics are reserved for more serious cases of impetigo, including bullous impetigo. The most common types of antibiotics taken as pills are types of penicillin or related medications called cephalosporins. If someone has a penicillin allergy, the treatment is usually with erythromycin (or other similar medicines such as clarithromycin [Biaxin] or azithromycin [Zithromax]). For some infections caused by resistant bacteria, clindamycin or trimethoprim-sulfamethoxazole (Bactrim) may be required.
Keep the skin clean and dry and avoid any further injury. Use the medication the physician prescribes. If the rash becomes more extensive, becomes more painful, or worsens in any other way, contact a physician or get evaluated in the emergency department.
Prevent impetigo by avoiding contact with others who have this skin infection. It also helps if to keep skin clean, dry, and avoid scraping or injuring the skin.
Impetigo is easy to treat. Complications occur very infrequently. One rare, but potentially serious complication is inflammation of the kidney. This can occur because of a complex immune reaction to the bacteria and is called glomerulonephritis. If someone has blood in their urine, facial or skin swelling, or a rise in blood pressure, he or she should see a physician immediately, since these may be symptoms of kidney involvement.
Medically reviewed by Norman Levine, MD; American Board of Dermatology
Feaster, T., and J. Singer. "Topical Therapies for Impetigo." Pediatric Emergency Care 26.3 Mar. 2010: 222-227.
Geria, A., and R. Schwartz. "Impetigo Update: New Challenges in the Era of Methicillin Resistance." Cutis 85.2 Feb. 2010: 65-70.