Key Takeaways
- Impetigo is a highly contagious superficial skin infection, most common in children ages 2 to 5 but common in adults too. More than 3 million U.S. cases occur each year.[3]
- It is caused by Staphylococcus aureus and group A Streptococcus, with two forms: nonbullous (about 70 percent, honey-colored crusts) and bullous (about 30 percent, toxin-producing S. aureus blisters).[6][7]
- Limited nonbullous impetigo responds to topical mupirocin 2% or retapamulin 1%. A Cochrane review found topical antibiotics at least as effective as oral antibiotics for limited disease.[2][1]
- Extensive, multilesional, or bullous disease needs oral antibiotics such as dicloxacillin or cephalexin, with doxycycline or clindamycin when MRSA is suspected.[1]
- You are contagious until lesions are dry and crusted or you have been on treatment for 24 to 48 hours. Cover lesions and wash linens and towels daily.[4][7]
- With treatment, impetigo usually clears in about 10 days; untreated it takes 14 to 21 days, and roughly 20 percent of cases resolve on their own.[7]
- Complications are rare but include post-streptococcal glomerulonephritis (a kidney problem) and ecthyma, a deeper ulcerating skin infection.[5][7]
Impetigo is the kind of skin infection that spreads through a household or a classroom faster than people expect, largely because no one realizes how contagious it is until a second or third case shows up. It is a superficial infection, meaning it stays in the top layers of the skin rather than spreading deeper, and in most patients it is mild and clears with simple treatment. What makes it worth taking seriously is not the severity of the sores themselves but how easily they move from person to person and, in a small number of cases, a delayed kidney complication that can follow the skin infection.
This guide covers what impetigo is, why it appears, how long it lasts, the difference between the two main types, when topical cream is enough versus when you need pills, and when the infection warrants a same-day visit. Every clinical claim is cited to a primary source.
What Is Impetigo?
Impetigo is a common, highly contagious bacterial infection of the superficial layers of the skin, the epidermis.[7] It is also called school sores in some places, a name that reflects how readily it passes among children.[6] It starts as small red sores or blisters that break open, leak fluid for a few days, and then crust over with a characteristic golden or honey-colored scab.[4]
The bacteria responsible are group A Streptococcus (Streptococcus pyogenes) and Staphylococcus aureus, often working alone or together.[5] What matters for treatment is that both organisms need to be covered, which shapes the choice of antibiotic. Diagnosis is made by looking at the skin; a swab or culture is usually not needed unless the infection is severe, recurrent, or part of an outbreak.[3]
Nonbullous vs Bullous Impetigo
Impetigo comes in two forms that look different and, importantly, have different causes and treatment implications.
| Feature | Nonbullous (impetigo contagiosa) | Bullous |
|---|---|---|
| Frequency | About 70 percent of cases[3] | About 30 percent of cases[3] |
| Cause | S. aureus, group A Streptococcus, or both[5] | Almost always toxin-producing S. aureus[5] |
| Appearance | Small blisters that rupture and form thick honey-colored crusts[5] | Larger fluid-filled blisters that stay intact longer before breaking[6] |
| Typical age | Children and adults | Most common under age 5, especially infants[7] |
| Treatment | Topical antibiotic if limited; oral if widespread[1] | Oral antibiotics, since the infection sits under the blister[7] |
The distinction matters clinically. Topical creams work well when there are only a few crusted sores, but they cannot reliably reach bacteria trapped beneath an intact blister or spread across many lesions. That is why bullous disease and extensive disease are treated with oral antibiotics.[1][7]
What Causes Impetigo and Who Gets It?
Impetigo develops when staph or strep bacteria get into the skin through a break in the skin's surface. In many cases the break is something small and unremarkable, a scratch, an insect bite, a rash, or skin cracked from eczema. Scratching itchy eczema or chickenpox is a classic entry point.[6] Less often, impetigo develops on skin that never appeared broken.[6]
Because the bacteria enter through damaged skin, certain conditions and situations raise the risk. Disrupted skin from eczema, psoriasis, or bug bites is one. Others include crowded living conditions, hot and humid climates, poor hygiene, malnutrition, and diabetes. Daycare centers, schools, shelters, and military training settings are common sites of spread.[4][3] Contact sports, especially wrestling, also carry a higher risk because of skin-to-skin contact.[6]
Is Impetigo Contagious? How It Spreads
Yes, and this is the single most important thing to understand about impetigo. It is highly contagious and spreads primarily through close contact with an infected person or with drainage from the sores.[5] In a household, the bacteria frequently move to other family members; in schools and daycares, they move between children in close contact.[4]
It can also spread indirectly through shared objects, towels, clothing, sports equipment, sheets, or toys.[6] A person can also spread the infection to another part of their own body by touching a sore and then scratching elsewhere, which is why covering lesions and keeping hands clean matters.[5]
The incubation period, the time from exposure to first sores, is about 10 days when caused by group A strep.[4] That long lag is part of why outbreaks can seem to come from nowhere: the original case may have already healed by the time new cases appear.
What Does Impetigo Look Like?
Impetigo usually appears on exposed skin, most often around the nose and mouth, but it can occur anywhere on the body including the arms and legs.[4] The typical sequence looks like this:
- First, small red bumps or pimples appear, and they may itch.[4]
- Over four to six days, those bumps turn into blisters that rupture and leak a clear fluid or pus.[3]
- The ruptured sores then crust over with the signature honey-colored, golden, or yellow-brown scab.[5]
- In bullous impetigo, larger fluid-filled blisters form and may survive longer before breaking.[6]
The crusts are the most recognizable sign and the reason impetigo is easy for a clinician to identify at a glance. Healing eventually follows as the crusts dry and flake away. Most lesions heal without scarring, though some people notice temporary changes in skin color afterward.[4][7]
How Long Does Impetigo Last?
Untreated, impetigo typically resolves on its own in about 14 to 21 days, and roughly 20 percent of cases clear without any treatment.[7] With treatment, most cases clear in about 10 days.[7] The more practical reason to treat is not the speed of healing alone; it is that starting antibiotics makes you far less contagious within a day or two, which is what stops the infection from moving through a household or classroom.[5]
Impetigo vs Cold Sore vs Hand, Foot, and Mouth
Several common skin conditions get mistaken for impetigo, and the distinction changes how they are treated. Impetigo is bacterial; cold sores and hand, foot, and mouth disease are viral.
| Condition | Cause | Distinguishing features | Treatment |
|---|---|---|---|
| Impetigo | Bacteria (staph, strep) | Honey-colored crusts, often around nose and mouth; very contagious[5] | Topical or oral antibiotics[1] |
| Cold sore (herpes simplex) | Virus (HSV-1) | Clusters of small blisters on the lip, preceded by tingling; crust over but not honey-colored | Antivirals; resolves on its own |
| Hand, foot, and mouth | Virus (coxsackievirus) | Sores in the mouth plus a rash on palms and soles; may have fever | Symptom relief; resolves on its own |
If you are unsure which one you are looking at, the presence of thick, golden, honey-colored crusting points strongly toward impetigo, which is treatable and should be assessed by a clinician because of how contagious it is.[3]
Topical Treatment: Mupirocin and Retapamulin
For limited, uncomplicated nonbullous impetigo, meaning a small number of sores with no fever and no spreading infection, a topical antibiotic is the preferred treatment.[1][3] The two agents recommended by U.S. guidelines are:
- Mupirocin 2% ointment, applied directly to the sores.
- Retapamulin 1% ointment, applied twice daily for five days.[1][3]
The evidence supporting a topical-first approach is solid. The 2012 Cochrane review of interventions for impetigo found that topical antibiotics were more effective than placebo and at least as effective as oral antibiotics for limited nonbullous disease.[2] A separate IDSA guideline recommends topical agents over oral therapy for limited, nonbullous impetigo.[1] A newer topical quinolone, ozenoxacin 1% cream, is another option with activity against MRSA, though it is used less often.[1]
Two practical points. First, gently removing the crust with soap and water before applying the ointment helps the antibiotic reach the skin beneath.[7] Second, wash your hands after applying it, since the tool of treatment can also be a tool of spread if you touch sores and then touch other skin or surfaces.
Oral Antibiotics: When and Which
Oral antibiotics are recommended when topical treatment is not enough: when there are many lesions, when the infection is bullous, when there are systemic signs like fever, when it is part of an outbreak, or when topical therapy has not worked within a few days.[1][3]
The standard first choices for adults are dicloxacillin or cephalexin, both of which cover staph and strep.[1][3] When MRSA is suspected, confirmed, or common in the community, the alternatives are doxycycline or clindamycin.[1][8] This MRSA consideration has grown more important over the last two decades, as community-associated MRSA has become a frequent cause of skin infections.[8]
Regardless of which antibiotic is used, finish the full course as prescribed, even if the sores look better in a few days. Stopping early raises the risk the infection returns and adds to antibiotic resistance.
Topical vs Oral: The Decision
| Clinical picture | Recommended approach | Example |
|---|---|---|
| A few crusted sores, no fever, otherwise well | Topical antibiotic | Mupirocin or retapamulin[1] |
| Many lesions, spreading, or not improving after several days | Oral antibiotic | Dicloxacillin or cephalexin[3] |
| Bullous impetigo or blisters | Oral antibiotic | Dicloxacillin or cephalexin[7] |
| Fever, pain, or spreading redness | Same-day evaluation | May need broader treatment[1] |
| MRSA suspected or confirmed | Oral antibiotic active against MRSA | Doxycycline or clindamycin[8] |
The split is straightforward: limited disease gets a cream, extensive or bullous disease gets pills, and anything with fever or spreading redness deserves prompt medical attention rather than self-treatment.
When Can I Return to Work or School?
This is the question parents and employees actually ask, and the guidance is reassuringly specific. People with impetigo can return to school, daycare, or work once they have started appropriate antibiotic treatment and their sores are covered.[5] The CDC suggests staying home for at least 12 hours after starting antibiotics, and the American Academy of Pediatrics extends that to 24 hours for young children.[5]
Complications and Red Flags
Most cases of impetigo are mild and resolve without lasting harm. Complications are uncommon but worth knowing because one of them develops late, after the skin has already healed.
- Post-streptococcal glomerulonephritis (PSGN). A rare delayed kidney complication that most often appears one to two weeks after the skin infection clears, caused by an immune reaction to the strep bacteria rather than the bacteria themselves.[5] It can cause blood or protein in the urine, swelling, and high blood pressure. A small share of patients, roughly 5 percent, may develop glomerulonephritis.[7]
- Ecthyma. A deeper form of impetigo that ulcerates through the full thickness of the skin, producing painful, punched-out sores that heal with scarring.[7]
- Cellulitis. Spread of the infection into deeper tissue, which appears as red, warm, tender, spreading skin and can become serious.[7]
You have fever, spreading redness, worsening pain, or the sores are not improving after a few days of treatment. Also seek care if you notice swelling, tea-colored or bloody urine, or puffiness in the weeks after a skin infection, as these can signal the kidney complication PSGN.[5]
Prevention and Home Care
Because impetigo spreads so easily, prevention is mostly about interrupting the hand-to-sores cycle. Keep sores covered with a bandage or clothing, wash hands frequently, and avoid touching or scratching the lesions.[5] Wash clothing, linens, and towels used by the infected person daily, and do not share them with others until they are washed.[5]
At home, trimming nails and washing hands after touching the sores reduces the chance of spreading the infection to other parts of the body or to other people.[5] There is no firm evidence that cleaning the crusts or using over-the-counter antiseptics adds meaningfully to antibiotics, so focus on the antibiotics plus hygiene rather than on elaborate topical routines.[2]
Frequently Asked Questions
About 10 days with treatment, and 14 to 21 days without it. Roughly 20 percent of cases clear on their own.[7]
Antibiotics make you far less contagious within 12 to 24 hours. You can return to school or work once you are on treatment and the sores are covered.[5]
No. Impetigo is a bacterial infection that forms honey-colored crusts, while a cold sore is caused by the herpes virus and usually appears as a cluster of blisters on the lip, often with prior tingling. They look different and are treated differently.[6]
Yes, recurrence is possible, especially if the skin barrier keeps breaking down (for example, from scratching eczema) or if someone in the household carries the bacteria and keeps re-exposing others.[3]
Cover the sores, wash hands often, avoid touching or scratching the lesions, and wash towels, clothing, and linens daily without sharing them. Start antibiotics as soon as possible, since that reduces contagiousness within a day.[5]
Most cases are caused by ordinary staph and strep, not MRSA. But MRSA can cause impetigo and has become more common in the community. When MRSA is suspected or confirmed, clinicians use antibiotics such as doxycycline or clindamycin that work against it.[8]
See a clinician for any suspected impetigo, and seek prompt care if you have fever, spreading redness, worsening pain, many lesions, or blisters. Also seek care for swelling, bloody or tea-colored urine, or puffiness in the weeks after a skin infection, since these can signal a kidney complication.[5]
References
- Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clinical Infectious Diseases. 2014;59(2):147-159. doi:10.1093/cid/ciu296
- Koning S, van der Sande R, Verhagen AP, et al. Interventions for impetigo. Cochrane Database of Systematic Reviews. 2012;1:CD003261. doi:10.1002/14651858.CD003261.pub3
- Trang DT, Buck EC, Schoenherr DT. Impetigo: Rapid Evidence Review. American Family Physician. 2026;113(2):175-180. PubMed PMID 41839109
- Centers for Disease Control and Prevention. About Impetigo (Group A Strep). Updated 2025. cdc.gov
- Centers for Disease Control and Prevention. Clinical Guidance for Group A Streptococcal Impetigo. Updated 2025. cdc.gov
- American Academy of Dermatology. Impetigo: Overview. aad.org
- Nardi NM, Schaefer TJ. Impetigo. StatPearls. Updated 2023. NCBI Bookshelf
- Daum RS. Clinical practice. Skin and soft-tissue infections caused by methicillin-resistant Staphylococcus aureus. New England Journal of Medicine. 2007;357(4):380-390. doi:10.1056/NEJMcp070747