Impetigo

What is impetigo?

Impetigo is a common and very contagious bacterial infection of the top layers of the skin. It causes red sores or blisters that break open, leak fluid, and then dry into a crust that is often described as honey-colored. The infection usually stays on the surface of the skin and, in most cases, it is mild and clears well with treatment. Because it spreads easily through close contact, it tends to move quickly through households, daycare centers, schools, and sports teams.

Impetigo can affect people of any age, but it is most often seen in young children, particularly those between about two and five years old. Adults can also develop it, especially if they have another skin problem such as eczema (a chronic itchy skin condition), a cut, an insect bite, or a weakened immune system. Understanding what impetigo is, how it spreads, and how it is treated can help families manage an outbreak calmly and reduce the chance of passing it on. Skin infections such as impetigo are generally assessed and managed by primary care doctors, pediatricians, or specialists in dermatology, the branch of medicine that deals with the skin, hair, and nails.

Impetigo symptoms

Impetigo symptoms usually appear a few days after the bacteria enter the skin. The sores most often develop on exposed areas, particularly around the nose and mouth, and on the hands, arms, and legs. In babies, the diaper area and skin folds may be involved. Common symptoms include:

• Small red spots or bumps that quickly turn into blisters or sores
• Sores that burst, leak clear or yellowish fluid, and then form a yellow-brown or honey-colored crust
• Itching or mild soreness around the affected skin
• Sores that spread to nearby skin or to other parts of the body, often after scratching
• Larger, fluid-filled blisters that may be clear at first and then cloudy
• Swollen glands (lymph nodes) near the affected area in some cases
• Deeper, painful sores with a thick crust in a less common, more serious form

Doctors usually describe three types of impetigo, and the symptoms differ somewhat between them:

• Non-bullous impetigo is the most common type. It begins as small red sores that break open and crust over with the typical honey-colored scab. The sores are often itchy but not usually painful. This form frequently starts around the nose and mouth.
• Bullous impetigo causes larger blisters, called bullae, filled with fluid. These blisters may stay intact for a day or two before they break, leaving a thin, moist, raw-looking area with a rim of skin around the edge. It is more common in infants and young children and often affects the trunk, arms, legs, and diaper area.
• Ecthyma is a deeper and less common form in which the infection reaches further into the skin. It produces painful, pus-filled sores that develop into thick, dark crusts and may leave scars once they heal.

Fever and feeling generally unwell are not typical of simple impetigo. If these symptoms are present, it may suggest that the infection has spread deeper or more widely, and medical review is advisable.

Causes and risk factors

The main impetigo causes are two types of bacteria: Staphylococcus aureus (often shortened to “staph”) and Streptococcus pyogenes (a form of “strep” bacteria, also called group A streptococcus). These bacteria can live harmlessly on the skin or in the nose of many healthy people. Infection develops when they get through the skin’s protective barrier, usually through a small break such as a scratch, an insect bite, a cut, a graze, or skin damaged by eczema, chickenpox, or a cold sore. When impetigo appears on skin that was otherwise healthy, doctors sometimes call it primary impetigo; when it develops on skin already damaged by another condition, it is called secondary impetigo.

Impetigo spreads through direct skin-to-skin contact with the sores or the fluid they release, and indirectly through items such as towels, bedding, clothing, and toys that have touched the infected skin. Scratching the sores and then touching other parts of the body can spread the infection across the skin. A person is generally considered contagious until the sores have crusted over and healed, or until they have been on effective antibiotic treatment for at least 24 to 48 hours, depending on local medical guidance.

Factors that increase the risk of developing impetigo include:

• Age: young children, particularly those in daycare or preschool, are most commonly affected
• Close contact: living in a crowded household or spending time in schools, camps, or team sports where skin touches skin
• Warm, humid weather, which makes it easier for bacteria to grow and spread
• Broken skin from cuts, scrapes, insect bites, or scratching
• Existing skin conditions such as eczema, scabies, or chickenpox
• A weakened immune system, for example from diabetes, certain medicines, or other illnesses
• Poor access to handwashing or shared use of towels and personal items

Impetigo diagnosis

In most cases, impetigo diagnosis is made by a doctor simply looking at the skin. The characteristic honey-colored crusts, the location around the nose and mouth, and the rapid spread of the sores are usually enough for an experienced clinician to recognize the condition. The doctor will typically ask when the sores started, whether anyone else in the household or school has similar sores, whether the person has other skin conditions, and whether any treatment has already been tried.

Laboratory tests are not needed for most straightforward cases. However, your doctor may take a swab from the fluid or crust of a sore and send it to a laboratory for a bacterial culture. This test grows the bacteria so that the exact type can be identified and tested against different antibiotics. A culture is more likely to be recommended when:

• The infection has not improved after a full course of the first antibiotic
• The sores keep coming back
• There is concern about antibiotic-resistant bacteria, such as MRSA (methicillin-resistant Staphylococcus aureus, a strain of staph that does not respond to several common antibiotics)
• There is an outbreak in a group setting and public health teams need to know the cause
• The person is very unwell or the infection is widespread

Imaging tests such as X-rays or scans are not used to diagnose impetigo, because the infection is on the surface of the skin. Blood tests are also rarely needed unless there are signs of a deeper infection or complications. In some cases, a doctor may consider other conditions that can look similar, such as cold sores (caused by the herpes simplex virus), fungal skin infections, eczema flares, or contact dermatitis, and may use the history and examination to tell them apart.

Impetigo treatment options

The goals of treatment are to clear the infection, relieve symptoms, prevent spread to others, and reduce the small risk of complications. Impetigo treatment options depend mainly on how many sores there are, how large the affected area is, the type of impetigo, and the person’s general health.

Skin care and hygiene. Whatever medical treatment is used, gentle care of the skin is part of managing impetigo. Doctors usually recommend washing the sores gently with soap and warm water to loosen and remove crusts, then patting the skin dry. Covering the sores loosely with a clean gauze dressing or clothing can help prevent scratching and reduce spread. Keeping fingernails short and washing hands frequently are also commonly advised.

Observation. Mild impetigo can sometimes clear on its own over two to three weeks. Even so, most doctors recommend treatment, because antibiotics shorten the illness, reduce the time a person is contagious, and lower the chance of the infection spreading or worsening. Waiting without treatment is generally not advised for children in daycare or school, or for anyone with widespread sores.

Topical antibiotics. For a small number of sores in a limited area, the standard treatment is an antibiotic cream or ointment applied directly to the skin. Commonly prescribed options include mupirocin and retapamulin, and in some regions other topical agents are used. The cream is usually applied two to three times a day for about five to seven days, after gently removing any crusts. Some guidelines suggest that an antiseptic cream, such as hydrogen peroxide cream, may be considered for very localized, mild cases. Your doctor will decide which product is suitable.

Oral antibiotics. If the impetigo is widespread, involves several areas of the body, is the bullous type, is not responding to topical treatment, or if the person has a weakened immune system, your doctor may prescribe antibiotics taken by mouth. Typical choices are antibiotics from the penicillin or cephalosporin families, and alternatives are available for people who are allergic to these. If MRSA is suspected or confirmed, a different oral antibiotic that targets resistant bacteria may be selected based on the culture results. Courses usually last about seven days. It is important to finish the full course even if the skin looks better sooner, so that the infection is fully cleared.

Treating the underlying skin condition. When impetigo develops on top of eczema, scabies, or another skin disease, that condition also needs to be managed. Otherwise the skin barrier remains damaged and the infection may return.

Procedures and surgery. Surgery is not part of impetigo treatment. In the rare situation where a deeper abscess (a collection of pus) forms, a doctor may need to drain it in the clinic, but this is uncommon with impetigo itself. Rehabilitation is not required, because the condition does not affect movement or function.

Most people see improvement within a few days of starting an appropriate antibiotic. If there is no improvement after about three days, or if the sores get worse, it is reasonable to go back to the doctor. A different antibiotic may be needed, or a swab may be taken to check for resistant bacteria.

Living with impetigo and outlook

For the large majority of people, impetigo is a short-lived, uncomfortable but not dangerous illness. With treatment, the sores usually stop spreading within a couple of days and heal within one to two weeks. Non-bullous and bullous impetigo typically heal without leaving scars, although the skin may look slightly lighter or darker for some weeks afterward before returning to normal. Ecthyma, the deeper form, is more likely to leave a scar because it damages the lower layers of the skin.

Complications are uncommon, but they can happen. These include cellulitis (a deeper infection of the skin and the tissue beneath it), which causes spreading redness, warmth, swelling, and pain; and, rarely, a kidney problem called post-streptococcal glomerulonephritis, which can follow a strep infection and may cause dark or bloody urine, swelling, and high blood pressure a week or more after the skin infection. In infants and people with weakened immune systems, bullous impetigo can occasionally lead to a more widespread reaction to bacterial toxins. These outcomes are rare, and prompt treatment lowers the risk further.

Impetigo can come back, especially if the bacteria remain in the nose or on the skin, or if an underlying skin condition is not controlled. Recurrent infections may prompt your doctor to swab the nose of the affected person and close household members and, if staph is found, to prescribe a short course of antibiotic ointment inside the nostrils to reduce carriage. Practical steps that families are often advised to take during an infection include keeping the sores covered, not sharing towels, washcloths, bedding, or clothing, washing these items in hot water, and keeping children out of school or daycare until the sores have crusted and dried or until they have had at least 24 to 48 hours of antibiotic treatment, in line with local rules.

Frequently asked questions

What does impetigo look like at the start?

Early impetigo often looks like a cluster of small red spots or tiny blisters, frequently near the nose or mouth or around a scratch or insect bite. Within a day or two the spots break open, release fluid, and dry into the honey-colored or yellow-brown crusts that are typical of the infection. Because early sores can resemble other skin problems such as cold sores or eczema, a doctor’s assessment is the most reliable way to tell them apart.

How do you catch impetigo?

Impetigo is passed on through direct contact with the sores or the fluid they leak, and through contact with items that have touched infected skin, such as towels, bedding, clothing, and toys. The bacteria then enter through small breaks in the skin. It spreads most easily among young children and in crowded settings. Once the sores have dried and crusted, or after a day or two of effective antibiotic treatment, the risk of passing it on drops considerably.

How is impetigo diagnosed if it is not obvious?

Most of the time, impetigo diagnosis is based on the appearance of the sores and the history of how they developed. When the picture is unclear, when treatment has not worked, or when a resistant infection is suspected, your doctor may take a swab from a sore for a bacterial culture. This identifies the bacteria and shows which antibiotics will work against them. Blood tests and imaging are not normally needed.

What are the main impetigo treatment options for children?

For children with a few localized sores, an antibiotic cream applied to the skin for about five to seven days is usually the first choice, alongside gentle washing and covering of the sores. If the infection is widespread, blistering, or not responding to cream, an oral antibiotic is often prescribed. The specific medicine and dose depend on the child’s age, weight, allergies, and local patterns of bacterial resistance, so treatment is always guided by a doctor.

Can impetigo go away on its own without antibiotics?

Mild impetigo can sometimes clear without treatment over two to three weeks, but this is generally not recommended. Untreated impetigo stays contagious for longer, is more likely to spread over the body, and carries a small risk of complications. Antibiotics shorten the illness and reduce the time the person can pass the infection to others, which is especially important for children in school or daycare.

How long is impetigo contagious?

A person with impetigo is usually considered contagious until the sores have crusted over and dried, or until they have completed at least 24 to 48 hours of appropriate antibiotic treatment. Many schools and daycare centers have their own policies about when a child can return, so it is sensible to check with them. Covering the sores and practicing good hand hygiene further reduce the risk of spreading the infection during this period.

Does impetigo leave scars?

The common forms of impetigo, non-bullous and bullous, usually heal without scarring because they affect only the upper layers of the skin. Temporary changes in skin color at the site of the sores are common and normally fade over weeks to months. The deeper form, ecthyma, can leave permanent scars. Avoiding scratching and picking at the sores may help reduce the chance of scarring.

When to see a doctor

It is generally advisable to see a doctor whenever you think you or your child may have impetigo, because a diagnosis can be confirmed and treatment can shorten the infection and limit its spread. This is particularly important for infants, for people with eczema or other skin conditions, and for anyone with a weakened immune system. You should also go back to the doctor if the sores have not started to improve after about three days of treatment, if new sores keep appearing, or if the infection returns after it seemed to clear.

Seek urgent medical attention if any of the following red-flag signs appear:

• Fever, chills, or feeling very unwell alongside the skin sores
• Redness, warmth, or swelling spreading rapidly beyond the sores, or skin that is very painful to touch, which may indicate cellulitis
• Red streaks spreading from the sores toward the body
• Dark, cola-colored, or bloody urine, reduced urine output, or puffiness of the face, hands, or feet in the weeks after impetigo, which may signal a kidney problem
• Widespread blistering or peeling of the skin, especially in a baby
• Signs of dehydration in a young child, such as a dry mouth, no tears, or unusual drowsiness
• Difficulty breathing, a stiff neck, severe headache, or confusion
• Impetigo in a newborn, or in anyone with a seriously weakened immune system

These situations are uncommon, but they need prompt assessment, because deeper or more widespread infection can progress quickly and is easier to treat when caught early.