You get impetigo when certain bacteria, most commonly staph or strep, enter your skin through a break in its surface. That break can be as obvious as a cut or scrape, or as subtle as a patch of dry, cracked skin from eczema or a tiny insect bite. The bacteria then multiply in the top layers of skin, producing the characteristic crusty sores that make impetigo so recognizable. It typically takes about 10 days after exposure for sores to appear.
The Bacteria Behind It
Two types of bacteria cause impetigo: Staphylococcus aureus (staph) and group A Streptococcus (strep). Staph is the more common culprit today and is responsible for nearly all cases of the blister-forming type. Strep tends to cause the classic honey-crusted sores. Sometimes both bacteria are present in the same infection.
These bacteria are common. Many people carry staph on their skin or inside their nose without any problems. Impetigo develops when the bacteria find an entry point, a spot where the skin’s protective barrier has been disrupted, and conditions are right for them to take hold.
How the Bacteria Get In
Healthy, intact skin is a surprisingly effective shield. Impetigo almost always starts where that shield has been compromised. Common entry points include:
- Cuts, scrapes, and scratches from everyday bumps and falls
- Insect bites that have been scratched open
- Eczema or other skin conditions that cause cracking or irritation
- Rashes from poison ivy, chickenpox, or allergic reactions
- Areas of skin irritation from friction, sunburn, or dryness
This is why impetigo is so common in children. Kids accumulate minor skin injuries constantly, from playground scrapes to picked mosquito bites, and each one is a potential doorway for bacteria.
Spreading From Person to Person
Contact with someone who already has impetigo is the single biggest risk factor for getting it. The fluid that oozes from impetigo sores is packed with bacteria, and direct skin-to-skin contact with that drainage is the most efficient route of transmission. This is why impetigo spreads so readily in daycares, schools, and households where children are in close physical contact throughout the day.
Indirect transmission matters too. Bacteria can survive on surfaces and fabrics long enough to infect someone else. Clothing, towels, bedding, and shared personal items can all carry the bacteria from one person to another. The CDC recommends washing clothing, linens, and towels used by someone with impetigo every day and not sharing them with others in the household.
Spreading It to Yourself
One of the trickiest things about impetigo is how easily it spreads across your own body. When you touch or scratch an existing sore and then touch another area of skin, you transfer bacteria to the new spot. This process, called auto-inoculation, is why a single sore near the nose can turn into patches on the arms, legs, or torso within days. Children are especially prone to this because they scratch without thinking about it, particularly when sores are itchy.
Keeping sores covered with a bandage helps limit this kind of self-spreading. It also reduces the chance of passing bacteria to other people.
Why Some People Are More Vulnerable
Impetigo overwhelmingly affects children. The highest rates are in kids under 10, with studies finding prevalence as high as 19% in children aged 0 to 4 and 5 to 9 in affected communities. Rates drop roughly in half by the 10 to 14 age range. Adults can absolutely get it, but their skin barrier tends to be more resilient and they’re less likely to be in the close-contact environments where it thrives.
Warm, humid conditions play a significant role. Sweat softens the skin and creates a moist environment where bacteria flourish, which is why impetigo is more common in tropical and subtropical climates and peaks during summer months in temperate regions. The highest burden of impetigo globally is in Oceania, where studies have found a median childhood prevalence above 40%. Rural communities and underprivileged populations also see disproportionately high rates, likely due to crowded living conditions and limited access to clean water for wound care.
Certain underlying conditions raise your risk. Eczema is a major one because it creates widespread breaks in the skin barrier. Diabetes, immune-suppressing medications, and any condition that weakens immune function can also make you more susceptible.
Two Types, Two Presentations
There are two forms of impetigo, and they look quite different because the bacteria behave differently in each case.
Non-bullous impetigo is the more common type, accounting for roughly 70% of cases. It starts as small red spots that quickly develop into blisters, which burst and leave behind the telltale golden or honey-colored crust. It tends to cluster around the nose and mouth but can appear anywhere.
Bullous impetigo produces larger, fluid-filled blisters that can reach an inch or more across. This form is caused specifically by staph bacteria that release toxins targeting the protein that holds skin cells together in the upper layers of the epidermis. When that protein is broken down, the layers separate and fluid fills the gap, forming a blister. These blisters are fragile and often burst, leaving a red, raw base with a thin, shiny crust. Bullous impetigo is more common in infants and toddlers.
How Long It Stays Contagious
Impetigo remains contagious as long as sores are draining or crusted and the person hasn’t started treatment. Once antibiotic treatment begins, whether a topical ointment for mild cases or oral antibiotics for more widespread infections, the contagious window closes relatively quickly. Most guidelines allow children to return to school or daycare after 24 hours of antibiotic treatment, provided sores can be kept covered.
Without treatment, impetigo sores can persist for weeks and continue spreading bacteria the entire time. The infection sometimes clears on its own, but treatment speeds healing, reduces spread, and lowers the small risk of complications like deeper skin infections.
Reducing Your Risk
Prevention comes down to two things: protecting your skin barrier and limiting exposure to the bacteria. Washing cuts, scrapes, and insect bites promptly with soap and water, then covering them with a clean bandage, removes the most common entry point. Keeping fingernails short helps reduce the damage from scratching, especially in children with itchy skin conditions.
If someone in your household has impetigo, basic hygiene measures make a real difference. Wash their towels, pillowcases, and clothes daily, and don’t share these items. Encourage frequent handwashing. Clean surfaces and toys that the infected person has touched. These steps sound simple, but they’re the most effective way to keep the infection from moving through a family or classroom.