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.
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:
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.
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:
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.
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: