Impetigo is a common, highly contagious bacterial skin infection that causes red sores, usually around the nose and mouth. It’s most common in children ages 2 through 5, though anyone can get it. The sores typically burst within about a week and develop a distinctive honey-colored crust. While it looks alarming, impetigo is not life-threatening and clears up well with antibiotic treatment.
What Causes Impetigo
Two types of bacteria cause impetigo: Staphylococcus aureus (staph) and group A Streptococcus (strep). Staph is now the more common culprit, responsible for roughly 80% of cases either on its own or alongside strep. These bacteria get in through breaks in the skin, even tiny ones you might not notice, like scratches, insect bites, or patches of eczema.
Once staph bacteria reach the skin’s surface, they produce toxins that break apart the “glue” holding skin cells together. This is what causes the characteristic blistering and peeling. The infection stays in the outermost layers of skin, which is why it typically heals without scarring in its most common form.
Several factors make infection more likely:
- Close contact with someone who already has impetigo, especially within a household
- Crowded settings like daycare centers, schools, or military facilities
- Hot, humid climates or tropical weather
- Existing skin conditions like eczema or scabies that compromise the skin barrier
- Cuts and scrapes from sports or outdoor play
- Poor hygiene, particularly inconsistent handwashing
The Three Types of Impetigo
Non-Bullous Impetigo
This is the most common form. It starts as small blisters or pus-filled bumps, often around the nose, mouth, hands, or feet. These quickly rupture and ooze for a few days before forming the telltale honey-colored crust over a reddened base. The sores spread easily to nearby skin through self-inoculation, meaning you touch a sore and then touch another area of your body, creating new “satellite” lesions. Nearby lymph nodes may swell slightly, but fever is rare.
Bullous Impetigo
Bullous impetigo looks quite different. Instead of small crusty sores, it produces larger, fluid-filled blisters that start clear or yellowish and eventually turn cloudy or dark. These blisters are fragile and tend to pop easily, leaving behind a red base with a scaly rim rather than a honey-colored crust. The blisters usually appear on the trunk and in skin folds (armpits, groin, neck creases) rather than the face. This form is caused almost exclusively by staph bacteria and is more likely to cause fever than the non-bullous type.
Ecthyma
Ecthyma is the most serious form. Unlike the other two types, which stay at the skin’s surface, ecthyma penetrates deeper into the skin. It produces ulcers that look “punched out” with dark purple edges and crusts that may be honey-colored or brownish-black. Because it goes deeper, ecthyma is more likely to leave scars and always requires oral antibiotics rather than topical treatment alone.
How Impetigo Spreads
Impetigo spreads through direct contact with the sores or with items that have touched them, like towels, clothing, or bedding. The bacteria can also spread from one part of your body to another through scratching or touching. Within households, once one person has impetigo, others often develop it quickly.
Children in daycare or school settings are especially vulnerable because of frequent close contact and shared surfaces. To reduce spread, keep sores covered with bandages, wash hands thoroughly and often, and avoid sharing personal items like towels or razors. Clothing and bedding used by someone with impetigo should be washed separately in hot water.
How It’s Diagnosed
Impetigo is usually diagnosed by appearance alone. The honey-colored crusting of non-bullous impetigo is distinctive enough that most clinicians can identify it on sight. The same goes for the large, fragile blisters of bullous impetigo. Lab cultures from the sores are not typically needed for straightforward cases but may be ordered if the infection doesn’t respond to initial treatment, which could suggest antibiotic-resistant bacteria.
Treatment and Recovery
How impetigo is treated depends on its type and how widespread it is. For non-bullous impetigo with just a few sores, a prescription topical antibiotic ointment (applied directly to the skin) is the standard approach. If there are more than five lesions, if lymph nodes are swollen, or if there are signs of deeper infection, oral antibiotics are used instead. All cases of bullous impetigo and ecthyma require oral antibiotics because of their greater severity or depth.
Treatment targets both staph and strep bacteria, since either or both may be involved. Most cases clear up within 7 to 10 days of starting antibiotics. Gently washing the crusted areas with soap and water before applying topical medication helps the antibiotic reach the infection more effectively.
Once treatment begins, impetigo typically stops being contagious within 24 to 48 hours. Many schools and daycares require children to stay home until they’ve been on antibiotics for at least 24 hours or until sores are no longer draining and can be covered.
Possible Complications
Impetigo almost always resolves without lasting problems, but in rare cases, complications can develop. The most notable is a kidney condition called post-streptococcal glomerulonephritis, which can occur when certain strains of strep bacteria are involved. This happens when the immune response to the infection inadvertently damages the kidneys’ filtering units, causing dark or bloody urine, swelling in the face or legs, and reduced urine output. It typically appears one to two weeks after the skin infection.
Other uncommon complications include the infection spreading deeper into the skin (cellulitis) or into the bloodstream. Interestingly, rheumatic fever, which can follow strep throat, has never been shown to develop after strep skin infections like impetigo.
Preventing Impetigo
Good hygiene is the most effective defense. Regular handwashing, keeping fingernails short, and cleaning cuts and scrapes promptly all reduce risk. If your child has eczema, insect bites, or other skin conditions that cause breaks in the skin, treating those promptly helps close the door to bacterial entry. In hot, humid weather, keeping skin clean and dry is particularly important since warmth and moisture create favorable conditions for the bacteria that cause impetigo.
If someone in your household has impetigo, give them their own towels, washcloths, and bedding until the infection clears. Avoid touching their sores, and make sure everyone in the house is washing hands frequently throughout the day.