Impetigo

The Facts

Impetigo, also known as pyoderma, is a contagious skin infection caused by bacteria. Bacteria enter cuts, scrapes, cracked skin or insect bites leading to the formation of small or large blisters. Primary impetigo is caused by direct bacterial infection on healthy skin. Secondary impetigo occurs on areas with a compromised skin barrier, such as an open cut or wound. People are more likely to get impetigo during warm, humid conditions.

Impetigo most commonly affects children between 2 and 5 but can affect older children and adults as well. It is usually seen around the nose and mouth in young children, but can be found on the arms, legs or trunk.

The Causes

Impetigo is caused by bacteria infecting the skin. The bacteria primarily responsible is Staphylococcus aureus (S. aureus), while Streptococcus pyogenes (S. pyogenes), a type of group A Streptococcus, is a less common cause. Both non-bullous and bullous forms of impetigo are typically caused by S. aureus. With non-bullous impetigo, no large blisters are present, while bullous impetigo is associated with larger, fluid-filled blisters. Ecthyma, a more serious type of skin infection, is more often associated with S. pyogenes. In some cases, both bacteria may be present.

These bacteria spread through direct or indirect contact:

Direct contact occurs through skin-to-skin interaction with someone who has impetigo, especially in crowded or close living conditions.
Indirect contact involves touching items contaminated with the bacteria, such as shared towels, bedsheets or clothing that have touched infected skin, or touching doorknobs or surfaces used by someone with impetigo.

In some cases, people carry the bacteria in their noses without showing symptoms. It can spread to other parts of the body through indirect contact and lead to repeated infections.

Individuals with pre-existing skin conditions such as eczema, insect bites, or damage to the skin barrier (e.g., burns, scratches, cuts or scrapes) are more vulnerable to infection due to a weakened skin barrier.

Symptoms And Complications

Impetigo typically begins as red bumps on the skin, often appearing on the face, arms, legs or trunk. These bumps are usually itchy which can lead to scratching and further spread of bacteria. The bumps may also cause mild pain and eventually form blisters.

Fluid-filled blisters typically burst and scab over, creating a honey-coloured crust. This is most common in non-bullous and bullous impetigo. In other cases, the blisters do not rupture but instead become painful, red-rimmed sores that heal more slowly. This deeper and more severe impetigo is known as ecthyma.

Varieties of impetigo include:

Non-bullous impetigo: the most common form. It starts as red sores that burst and form honey-coloured crusts. These sores are usually found around the mouth, nose, and extremities.
Bullous impetigo: characterized by large, fluid-filled blisters that burst and leave behind a thin brown crust. This type is more often seen on the trunk.
Ecthyma: a more severe form of impetigo involving ulcers. It begins as a blister filled with pus , which progresses into an open sore, rather than rupturing. Ecthyma appears as a sore with a thick brown or black crust and punched-out look, often surrounded by red or purple skin. If left untreated, it is more likely to leave scars.

Making A Diagnosis

To make a diagnosis of impetigo, your doctor will examine your skin and ask you questions about your symptoms and skin condition history. In most cases, no additional tests are needed. However, a skin swab may be taken for Gram staining and culture especially if the infection is severe or recurring. In rare cases, blood tests for streptococcal antibodies may be considered.

Treatment And Prevention

Your doctor will recommend a treatment plan based on the type and severity of infection. For most people, antibiotics are needed.

For mild impetigo, gently placing a warm water or saline-soaked towel on the skin for 10-15 minutes, 3-4 times a day, can help soften crusts and promote healing. Mild, localized cases are usually treated with topical antibiotic ointments like fusidic acid or mupirocin, applied to the skin several times a day for a few days.

More widespread or serious infections, like bullous impetigo or ecthyma, often need oral antibiotics, such as cephalexin. If their symptoms don’t improve within 48 hours, your doctor may adjust their treatment based on their test results.

To avoid passing the infection to others:

Wash your hands often, especially if you touch the infected area or blisters
Don’t share personal items such as towels, clothes or hair combs
Wash clothing and bedding in hot water and dry on high heat
Keep infected skin clean and covered
Throw away used tissues right after use and wash your hands afterwards
Children can return to school 24 hours after starting antibiotic therapy, but any draining lesions should be kept covered