Impetigo is highly contagious. It spreads easily through direct skin-to-skin contact and through shared items like towels, clothing, and bedding. Without treatment, a person remains contagious for as long as the sores are oozing or draining. With antibiotics, most people are considered safe to return to school or work after just 12 hours.
How Impetigo Spreads
The infection is caused by bacteria, most commonly staph (Staphylococcus aureus) or strep (group A Streptococcus). Both live on the skin’s surface and enter through any break in the skin barrier: a cut, scrape, insect bite, or patch of eczema. Once inside, the bacteria multiply quickly and produce the characteristic sores.
Impetigo spreads in two main ways. The first is direct contact with an infected person’s sores or the fluid draining from them. The second is indirect contact through contaminated objects. Towels, pillowcases, sports equipment, and toys can all carry the bacteria. This is why impetigo moves so quickly through daycare centers, classrooms, and sports teams where kids share gear and close physical contact is constant.
People with impetigo also spread it to themselves. The bacteria from one sore can travel on fingers to other parts of the body, creating new “satellite” lesions. This self-inoculation is a hallmark of the infection, particularly with the non-bullous form, where clusters of sores rapidly appear on the face and arms.
How Long You’re Contagious
The contagious window depends entirely on whether you get treatment. Without antibiotics, you remain infectious for as long as the sores are actively draining. That can stretch for weeks, since untreated impetigo often continues to spread across the skin and produce new lesions before eventually resolving on its own.
With antibiotics, the timeline shrinks dramatically. The CDC states that people can return to school or work at least 12 hours after starting antibiotic treatment, provided they also keep any exposed sores covered. The American Academy of Pediatrics follows the same 12-hour guideline for children returning to school or daycare, with one caveat: in outbreak situations or when a healthcare worker is infected, staying home for at least 24 hours after starting antibiotics is recommended.
It’s worth noting that “no longer contagious” and “fully healed” are not the same thing. The sores themselves may take a week or more to clear completely, but the risk of passing the infection drops sharply once antibiotics are on board and lesions are covered.
What Impetigo Looks and Feels Like
Impetigo comes in two forms, and recognizing them helps you act quickly to limit spread.
Non-bullous impetigo is the more common type. It starts as small blisters or pus-filled bumps that quickly rupture and leave behind a honey-colored crust over a red base. These sores tend to cluster on the face (especially around the nose and mouth) and on the arms and legs. They multiply fast through self-inoculation. Nearby lymph nodes may swell slightly, but fever is rare. This form is especially common in young children.
Bullous impetigo looks different. It produces larger, fluid-filled blisters that start clear or yellowish and gradually turn cloudy or dark. These blisters are fragile and rupture easily, leaving behind a red base with a scaly rim instead of the honey crust. Bullous impetigo tends to appear on the trunk and in skin folds like the armpits or groin, and it can even develop inside the mouth. There are usually fewer sores overall, but fever and other systemic symptoms are more common than with the non-bullous type.
Who Is Most at Risk
Children between ages 2 and 5 are the most frequently affected group. Their immune systems are still developing, they’re in close contact with other kids daily, and they’re more likely to have the scrapes and bug bites that give bacteria an entry point. But impetigo can affect anyone at any age, particularly in warm, humid climates where bacteria thrive on moist skin.
People with existing skin conditions like eczema or dermatitis face higher risk because their skin barrier is already compromised. Athletes in contact sports, military personnel in close quarters, and anyone living in crowded conditions are also more vulnerable.
Complications of Untreated Impetigo
Most cases of impetigo are superficial and heal without scarring, but leaving it untreated raises the stakes in two ways. First, untreated sores keep spreading, both on your own body and to the people around you. Second, when impetigo is caused by group A strep, a kidney condition called post-streptococcal glomerulonephritis can develop about three weeks after symptoms appear. This is most common in preschool-age children. The kidneys become inflamed, which can cause dark or bloody urine, swelling, and high blood pressure. Long-term kidney damage is rare but occurs more often in adults than children when it does happen.
Preventing Spread at Home
If someone in your household has impetigo, a few practical steps make a real difference. Keep the infected person’s towels, washcloths, bedding, and clothing separate from everyone else’s, and wash them in hot water after each use. Clean any surfaces they touch regularly.
Cover all visible sores with bandages, especially before going out. Frequent handwashing is essential for both the infected person and everyone else in the household. Avoid touching or scratching the sores, since that’s the fastest way to spread the bacteria to new areas of skin. Cut fingernails short to reduce the chance of picking at sores unconsciously, particularly with young children.
If your child has impetigo and has started antibiotics, they can return to daycare or school after 12 hours as long as exposed sores are covered. Keeping them home longer than necessary isn’t required, but making sure those bandages stay in place throughout the day is critical to protecting other kids.