Impetigo 101: Symptoms, Causes, and Treatment

Medically reviewed by Debra Sullivan, PhD, MSN, RN, CNE, COI on October 24, 2017Written by Marjorie Hecht

Introduction

Impetigo is a common, highly contagious bacterial skin infection.

It mostly affects young children and infants. But people of any age can get it from contact with someone who is infected.

Most impetigo is caused by Staphylococcus aureus bacteria. The infection isn’t usually serious, but sometimes complications may develop.

Topical antibiotics usually clear up impetigo in 7 to 10 days (1). It can also clear up on its own in 2 to 4 weeks, but you’ll have a greater risk of developing complications without antibiotics (2).

This article explains everything you need to know about impetigo, including its symptoms, causes, and how to treat it.

What is impetigo?

Impetigo (pronounced im-puh-ty-go). is caused by a Staphylococcus aureus or Streptococcus pyogenes bacterial infection on the outer layers of skin, the epidermis. The face, arms, and legs are the skin areas most often affected (3).

Anyone can get impetigo, but it’s the most common bacterial skin infection among children, affecting mostly 2- to 5-year olds (4, 5). In fact, it accounts for about 10 percent of skin problems seen in pediatric clinics (1).

The infection most often begins in minor cuts, insect bites, or a rash such as eczema — any place there is broken skin. But it can also occur on healthy skin.

It’s called primary impetigo when it infects healthy skin and secondary impetigo when it occurs in broken skin (6).

Impetigo is an old disease. The name dates back to 14th-century England and comes from the Latin word impetere, meaning “to attack.” Attack seems an appropriate name for this easily spread infection.

Contagion

The open sores are highly contagious, itchy, and sometimes painful. Scratching the sores can spread the infection from one place on your skin to another, or to another person. The infection can also spread from anything an infected person touches.

Because it spreads so easily, impetigo is also called the “school disease.” It can quickly spread from child to child in a classroom or day care center where children are in close contact. For the same reason, it also spreads easily in families.

Hygiene is key to controlling impetigo’s spread. If you or your child has impetigo, you need to wash and disinfect everything the infection might come in contact with, including clothes, bedding, towels, toys, or sports equipment (7).

Topical antibiotics can usually clear up impetigo in days, and shorten the length of time that the disease is contagious (1).

A global problem

Impetigo is a global disease that has remained at the same incidence levels for the last 45 years (8). An estimated 162 million children worldwide have impetigo at any one time (8).

Bacteria thrive in hot, moist conditions. So impetigo tends to be seasonal, peaking in the summer and fall in northern climates. But in warm and humid climates, it can occur year-round (1).

Impetigo is more prevalent in developing countries, and in the poor areas of industrial countries (8). A 2015 review of impetigo found the highest incidence in the 14 countries of Oceania (8). This same study recommended that more research and more attention be paid to impetigo as a public health problem (8).

SUMMARY: Impetigo is a contagious bacterial infection that mostly affects children. Antibiotic treatment clears it up and helps prevent its spread.

Common symptoms of impetigo

Reddish spots on the skin, often clustered around the nose and lips, are the first sign of the most common type of impetigo.

The sores quickly grow into blisters, ooze and burst, and then form a yellowish crust. The crust is often described as honey-colored. The clusters of blisters may expand to cover more of your skin.

The sores are unsightly, itchy, and occasionally painful. After the crust phase, they leave red marks that fade without leaving scars.

Infants often have a less common type of impetigo, with larger blisters around the diaper area or in skin folds. These fluid-filled blisters soon burst, leaving a scaly rim called a collarette (4).

Impetigo can be uncomfortable. Occasionally, it may involve swollen glands in the area of the outbreak. Fever and swollen glands can occur in more severe cases (6).

SUMMARY: The main symptom of impetigo is itchy red blisters that crust over.

Types of impetigo

There are three types of impetigo distinguished by the bacteria that cause them and the sores they form.

Nonbullous

Nonbullous, also called impetigo contagiosa, is mainly caused by Staphylococcus aureus. It’s the most common form of impetigo, an estimated 70 percent of cases (1).

Nonbullous impetigo can also be caused by Streptococcus pyogenes or by a combination of both staph and strep. A small number of cases, 5 to 10 percent, are caused by strep bacteria alone (6).

It usually starts with reddish spots that develop into small red blisters around the mouth and nose. The blisters range in size from 1 to 2 centimeters in diameter (.39 to .78 inch) (9). The clusters of blisters may spread to other skin areas.

After a few days, the blisters burst and develop a brownish-yellow crust. The surrounding skin can look red and raw.

Nonbullous impetigo is itchy, but not painful. When the crusts heal, there are reddish spots that fade and don’t leave scars.

Nonbullous impetigo rarely occurs in children under 2 (9).

Bullous

Bullous impetigo is caused by Staphylococcus aureus.

It usually forms larger blisters or bullae filled with a clear fluid that becomes darker and cloudy. The blisters can be up to 2 centimeters in diameter (about .78 inch) (9).

Typically, the blisters begin on unbroken skin and aren’t surrounded by reddish areas (2). The blisters become limp and then burst open. Then a yellowish crust forms over the sore.

Bullous impetigo is most common in newborns, especially in the diaper area or neck folds (4, 10). For other ages, the blisters appear most often on the trunk and arms and legs.

The blisters usually leave no scars when they have healed.

Ecthyma

Ecthyma is caused by Streptococcus pyogenes, Staphylococcus aureus, or both (6).

The infection forms small, pus-filled sores with a thicker crust. But ecthyma goes deeper into the skin than the other forms of impetigo, and it can be more severe. Ecthyma sometimes may be accompanied by swollen glands.

Ecthyma blisters can be painful and can develop into larger, deeper sores, between 0.5 and 3 centimeters in diameter (0.3 to 1.2 inches). These sores progress to have a thick crust surrounded by reddish-purple skin.

Most often ecthyma appears on your buttocks, thighs, legs, ankles, and feet. Sometimes untreated nonbullous or bullous impetigo can develop into ecthyma (2).

The ecthyma lesions heal slowly and may leave scars after they heal.

SUMMARY: There are three types of impetigo: nonbullous, bullous, and ecthyma. They’re distinguished by the type of blister. About 70 percent of impetigo is nonbullous.

What causes impetigo?

Impetigo is a bacterial infection. Your skin surface and the inside of your nose are normally home to large numbers of “friendly” or commensal bacteria that help protect you from disease-causing bacteria such as Staphylococcus aureus and Streptococcus pyogenes (11).

Your commensal bacteria work to keep down the population of pathogenic bacteria by producing substances that are toxic to the pathogens, depriving them of nutrients, among other measures (11).

But strains of these staph or strep bacteria can take advantage of a break in the skin from a cut, scratch, insect bite, or rash to invade and colonize, causing impetigo (9).

The bacteria can also colonize and cause an infection on normal skin (12). It’s not known exactly why this happens.

Within about 10 days of bacteria colonization, impetigo blisters appear (12). The way it works is that the Staphylococcus aureus and Streptococcus pyogenes bacteria produce toxins that break apart your top skin layers, causing blisters to form (11).

In many cases, the bacteria are already on site, waiting for an opportunity to colonize:

Staphylococcus aureus and Streptococcus pyogenes bacteria are normally carried in the nose by between 20 and 50 percent of the general population (13). An even larger percentage of people are intermittent carriers.

Further, about 10 to 20 percent of healthy people have Staphylococcus aureus bacteria in their perineum (the area between the genitals and the anus) (13).

For people who are Staphylococcus aureus carriers, infection is thought to be spread by the person from their nose or other area to the skin (9). In contrast, strep-caused impetigo usually begins with the strep bacteria spreading to the skin from a person with impetigo (13).

Normally strep doesn’t survive on skin for more than a few hours. It’s not known why the strep bacteria are able to stay on the skin of people who develop impetigo for 10 days, before the blisters appear (13).

Strains of strep bacteria behave differently. Research has shown that some strains of strep bacteria cause throat infections, while others cause skin infections (9, 12).

Why do some people carry staph and strep bacteria without developing impetigo? It’s thought that some individuals are more able to resist infection because of the chemical makeup of their skin and their general good health (9).

Other factors in impetigo

Other factors can make a difference in the growth of staph and strep bacteria that cause impetigo:

  • Poor hygiene aids the spread of bacteria. One study found that when child caretakers had an orientation program about the importance of handwashing, the incidence of impetigo in their group was 34 percent lower (9).
  • Disease-causing bacteria thrive in hot humid weather.
  • Working or living in close crowded conditions can promote impetigo spread. This includes the military, especially in tropical areas.
  • Sports that involve skin-to-skin contact, such as football, wrestling, or jiu-jitsu put you at risk.
SUMMARY: Staphylococcus aureus and Streptococcus pyogenes invade the skin to cause impetigo, by releasing toxins that break down the skin layer, forming blisters. Hot and humid weather, crowded conditions, and poor hygiene aid the spread of bacteria.

How does impetigo spread?

Impetigo is highly contagious. It spreads on direct contact with a skin sore or with anything that may have touched an open sore.

Though uncommon, impetigo can also spread by contact with bedding, underwear and clothes, towels and washcloths, toys, sports equipment, and anything else that came in contact with an open sore.

If you’re using a topical antibiotic, the sores are contagious until they stop oozing and dry up.

If you’re taking an oral antibiotic, the infection usually won’t be contagious after 24 to 48 hours (2).

SUMMARY: Impetigo easily spreads by direct or indirect contact.

At-risk populations

Children 2 to 5 years old, especially those in a day care center or play group, are the most at risk.

Adults and children are more at risk if they:

SUMMARY: Children in day care or play groups are most at risk for impetigo. Others at risk include those with skin ailments or compromised immune systems.

When should you see a doctor?

It’s a good idea to see your doctor if you suspect impetigo. Antibiotic treatment for impetigo speeds up healing and can stop the spread of infection for you (or your child) and others.

With treatment, impetigo usually heals in 7 to 10 days. If you have an underlying infection or skin disease, treatment may take longer to heal (1).

It’s likely that your doctor can diagnose impetigo by its appearance. But in a severe case, the doctor may want to culture the bacteria (14).

SUMMARY: Getting treated for impetigo speeds healing.

Treatment of impetigo

Treatment for impetigo depends on how widespread or severe the blisters are (6).

Antibiotics

The Infectious Diseases Society of America recommends treatment with topical antibiotics for 5 to 7 days (15).

The specific topical antibiotics recommended are mupirocin and fusidic acid (15). A 2003 meta-analysis of 16 studies found no significant difference between these two topical antibiotics (16).

If your impetigo is severe or widespread, oral antibiotics are recommended. These work more quickly than topical antibiotics (13). However some studies show no significant difference in cure rates between topical and oral antibiotics (6, 16).

The recommended oral antibiotics include anti-staphylococcal penicillins, amoxicillin/clavulanate (Augmentin), cephalosporins, and macrolides. Erythromycin was found to be less effective (4).

Note that oral antibiotics can have more side-effects than topical antibiotics, such as nausea (4).

Also, there is some evidence of antibiotic resistant staph in impetigo treatment (17).

Home treatments

You can aid the healing and the appearance of impetigo with home treatments, cleaning and soaking and bleach baths.

Cleaning and soaking the sores is recommended, three to four times a day. Make sure to wash your hands thoroughly after treating the impetigo sores.

Gently clean the sores with warm water and soap and then remove the crusts from nonbullous impetigo. Removing the crusts exposes the bacteria underneath (7). You can also soak the affected area in warm soapy water before removing the crusts.

Cleaning or soaking and crust removal should be done regularly until the sores heal. Dry the area and apply antibiotic ointment. Then cover the sores lightly with gauze.

For a minor outbreak, you can use an over-the-counter antibiotic ointment.

Apply it three times a day, after cleaning the area. Then cover the sore with a bandage or gauze.

Another home treatment is a 15-minute bleach bath with a very dilute solution of household bleach (2.2 percent). This reduces the bacterial level on the skin, but needs to be done regularly.

For a full-size bath, use one-half cup of bleach. A full bath usually has 80 liters (21 gallons) of water. Rinse off with warm water and pat dry. Note that some people may have an allergic reaction to bleach.

A 2004 study found no evidence showing that other disinfecting agents, such as chlorhexidine or povidone-iodine, were effective. However, this study noted that more research was necessary (17).

SUMMARY: Topical antibiotics for 5 to 7 days can help clear up your lesions faster. For widespread outbreaks, oral antibiotics may be necessary. Home treatments include regular cleaning or soaking the affected areas, light bandaging, and bleach baths.

Complications of impetigo

Complications of impetigo can occur but are relatively rare (1, 6). Generally, adults have a higher risk of complications (4).

About 1 to 5 percent of people with nonbullous impetigo get acute post-streptococcal glomerulonephritis, a serious disease involving inflammation of the small blood vessels in the kidneys (4).

Other complications of impetigo include:

  • cellulitis, a serious infection (Staphlococcus aureus) of the tissues under your skin, which can spread to the bloodstream
  • lymphangitis, an inflammation of the lymphatic channels
  • sepsis, a bacterial infection of the blood
  • scarlet fever, a rare bacterial infection caused by Streptococcus pyogenes
  • guttate psoriasis, a non-infectious skin condition that can infect children and young adults after a skin infection
  • Staphyloccus scalded skin syndrome (SSSS), another serious skin condition
SUMMARY: Complications of impetigo are rare, but can be serious.

How can you prevent impetigo and its spread?

Children with impetigo should stay home until the impetigo is no longer contagious. Adults who have impetigo in the contagious stage and who work in occupations that involve close contact with others should check with their doctor about when to return to work.

Good hygiene is number one for prevention:

  • Regular bathing and frequent handwashing can cut down on skin bacteria.
  • Cover any skin wounds or insect bites to protect the area.
  • Keep nails clipped and clean.
  • Don’t touch or scratch open sores. This will spread the infection.
  • Wash everything that comes in contact with the impetigo sores in hot water and some laundry bleach (7).
  • Change bed linens, towels, and clothing every day, until the sores are no longer contagious (7).
  • Clean and disinfect surfaces, equipment, and toys that may have come in contact with impetigo.
  • Don’t share any personal items with someone who has impetigo.
SUMMARY: Good hygiene is key in preventing the spread of impetigo. This includes cleaning everything that comes in contact with lesions. Children with impetigo should stay home until they are no longer contagious.

Bottom line

Impetigo is a highly contagious and unsightly bacterial skin infection that is generally not serious. It clears up faster with antibiotics and requires diligent good hygiene.

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