Bullous impetigo: symptoms, causes, diagnosis, treatment, and prevention of complications

Bullous impetigo is a contagious superficial bacterial skin infection characterized by the appearance of large, thin-walled, fluid-filled blisters, or bullae. Unlike typical non-bullous impetigo, which typically features pustules and a "honey-colored" crust, the bullous form is characterized by blisters that quickly rupture, leaving moist, scaly erosions with a thin, flaky border. [1]

The main causative agent of bullous impetigo is the toxin-producing Staphylococcus aureus. These strains secrete exfoliative toxins that damage the protein desmoglein 1, which is responsible for cell adhesion in the superficial layer of the skin. When the bonds between cells weaken, the top layer of the epidermis separates, and a blister forms. [2]

Bullous impetigo is most common in infants and young children, although it can affect people of any age. Babies have thinner skin, their immune system is still developing, and close contact with adults' hands, clothing, diapers, and surfaces facilitates the transmission of bacteria. [3]

Clinically, this form is important because it can appear frightening: the blisters are large, burst quickly, the skin becomes moist, and a "collar" of peeling skin remains around it. Some patients also experience malaise, fever, and swollen lymph nodes, which is less typical for non-bullous impetigo. [4]

Bullous impetigo must be differentiated from staphylococcal scalded skin syndrome, herpes, burns, allergic blistering reactions, autoimmune blistering dermatoses, and ecthyma. This is especially important in newborns, infants, immunocompromised patients, and in cases of widespread skin lesions. [5]

Sign	What are the characteristics of bullous impetigo?
The main causative agent	Toxin-producing Staphylococcus aureus
The main element	Large superficial blister with a thin lid
After opening the bubble	Wet erosion and flaky rim
Frequent areas	Face, torso, limbs, buttocks, perineum
Contagiousness	High, especially when in contact with secretions
Age risk	More often children, especially infants and preschoolers
Special danger	Confusion with more severe bladder conditions

Code according to ICD 10 and ICD 11

In the basic International Classification of Diseases, 10th revision, impetigo is coded under the section on infections of the skin and subcutaneous tissue. Impetigo is coded L01, while the more specific category L01.0 designates "impetigo of any organism and any site." That is, the basic version of the classification does not allocate a separate international code specifically for the bullous form. [6]

In the International Classification of Diseases, 11th revision, bullous impetigo is more precisely defined: code 1B72.0 corresponds specifically to bullous impetigo. The description of this category indicates that the disease is caused by certain strains of Staphylococcus aureus, which secrete toxins capable of breaking down desmoglein 1, causing the formation of well-demarcated blisters. [7]

System	Code	Formulation	Comment
ICD 10	L01	Impetigo	General section
ICD 10	L01.0	Impetigo of any organism and any localization	Suitable for bullous impetigo in the basic version of the classification
ICD 10	L01.1	Impetiginization of other dermatoses	It is used if a bacterial infection complicates an existing dermatosis.
ICD 11	1B72	Impetigo	General section
ICD 11	1B72.0	Bullous impetigo	The most accurate code for this form
ICD 11	EH11	Neonatal bullous impetigo	Listed as a separate related heading for newborns

Why do bubbles appear?

The blisters of bullous impetigo are caused not simply by mechanical rubbing of the skin, but by the action of a bacterial toxin. Staphylococcus aureus secretes exfoliative toxins A and B, which disrupt the adhesion of cells in the upper layers of the epidermis, causing the skin to separate and form a thin-walled cavity filled with fluid. [8]

The key target of the toxins is desmoglein 1. This protein helps skin cells adhere to each other, and its damage leads to superficial peeling of the epidermis. This is why the blisters in bullous impetigo are superficial, easily rupture, and leave erosions without deep ulceration. [9]

Bullous impetigo can occur even on seemingly intact skin. This distinguishes it from many cases of non-bullous impetigo, where bacteria are more often introduced through scratching, insect bites, abrasions, atopic dermatitis, scabies, or other barrier damage. [10]

However, any damage to the skin still increases the risk of infection. In a child with atopic dermatitis, itching, cracks, diaper rash, insect bites, or scratches, bacteria can more easily gain a foothold on the skin and spread to adjacent areas. [11]

The disease mechanism explains why bullous impetigo is sometimes compared to staphylococcal scalded skin syndrome. Both involve toxigenic strains of Staphylococcus aureus and damage to desmoglein 1, but in bullous impetigo the process is usually localized, while in staphylococcal scalded skin syndrome, the toxins spread systemically and cause extensive skin detachment. [12]

Mechanism	What's happening	How it appears on the skin
Staphylococcus aureus toxin	Damages intercellular connections	Bubbles appear
Desmoglein 1 lesion	The epidermal cells separate	The bubble is thin-walled and superficial
Opening the bubble	The lid breaks quickly	Wet erosion occurs
Drying of discharge	The liquid dries out	A thin crust is formed
Autoinfection	Bacteria are carried by hands	New outbreaks are emerging
Immature skin barrier in children	The skin is more easily damaged	The risk of spread is higher

What does bullous impetigo look like?

The typical feature of bullous impetigo is a rapidly appearing superficial blister. It can be small or reach several centimeters, has a thin cap, contains clear, cloudy, or yellowish fluid, and is usually easily ruptured. [13]

After the blister bursts, a moist, red or pink erosion remains, and a thin, flaky rim, called a collarette, is often visible around the edge. This collarette is an important clue for the physician because it shows where the blister cap used to be. [14]

The rash often appears on the face, trunk, limbs, buttocks, and perineum. In infants, lesions may occur in the diaper area, folds, around the navel, or in areas of friction. In adults, the location can vary, especially if there is skin damage, immune dysfunction, or close contact with a source of infection. [15]

Unlike non-bullous impetigo, the bullous form's "honey" crusts may be less pronounced because the primary process is the formation and rupture of blisters. Sometimes a thin, varnished surface, moist erosion, or soft crust remains, rather than the dense, golden crust typical of the classic non-bullous form. [16]

Bullous impetigo may be accompanied by itching, soreness, regional lymphadenopathy, fever, and malaise. If severe pain, rapidly spreading redness, hot, swollen skin, fever, or weakness occur, a deeper infection and complications should be ruled out. [17]

Sign	Bullous impetigo	Nonbullous impetigo
The main element	Large bubble	Papule, pustule, crust
Pathogen	Usually toxigenic Staphylococcus aureus	Staphylococcus aureus, Streptococcus pyogenes, or both
crusts	Often thin, after the blister has burst	Often dense "honey"
Localization	Face, torso, limbs, buttocks, perineum	Most often the face and exposed areas
Systemic symptoms	More likely to occur	Usually the patient feels satisfactory
Diagnostic risk	It must be distinguished from other bladder diseases.	It must be distinguished from herpes, dermatitis, and scabies.

Infectivity and transmission routes

Bullous impetigo is contagious because bacteria are present in the fluid from blisters, erosions, crusts, and objects that have come into contact with the affected skin. Transmission most often occurs through direct contact with the lesions, hands, towels, clothing, bedding, toys, and personal care items. [18]

Self-infection is a common cause of new lesions. A person touches a blister or erosion, and bacteria gets on their fingers and under their nails, then spreads to other areas of the skin. This is especially common in children, as they scratch their skin more often and don't always practice proper hand hygiene. [19]

Antibiotic therapy reduces a person's ability to transmit bacteria. The U.S. Centers for Disease Control and Prevention recommends that for impetigo, returning to school or work should be done no sooner than 12 hours after starting an appropriate antibiotic if the lesions are closed; in certain situations, such as an outbreak or work in a healthcare environment, a period of at least 24 hours may be considered. [20]

Until the infection subsides, the affected areas should be covered with clean bandages or clothing, if possible. Towels, clothing, and linens that have come into contact with the affected skin should be washed daily and not shared with other people until washed. [21]

Contagiousness is especially important in kindergartens, schools, sports clubs, families with several children, and neonatal units. If cases recur in a family or group, a physician may consider testing for Staphylococcus aureus and additional preventive measures. [22]

Route of transmission	Example	Prevention
Direct contact	Touching a blister or erosion	Close the outbreaks
Hands	The child touches the rash and face	Wash your hands and keep your nails short.
Towels	A shared towel in the family	Use separate towels
Clothes and underwear	Contact of tissue with discharge	Daily washing
Toys and care items	Especially in children	Regular cleaning
Children's group	Close contacts and shared items	Return after the start of treatment and closure of foci

Diagnostics

In most cases, the diagnosis of bullous impetigo is made clinically: the doctor evaluates the appearance of the blisters, their location, the rate of onset, the presence of erosions, crusts, fever, pain, lymph nodes, and contact with sick people. The typical presentation of superficial thin-walled blisters and erosions often allows for treatment to be initiated without waiting for laboratory tests. [23]

Culture of the discharge or fluid from the lesion may be useful if the diagnosis is unclear, the rash is widespread, the disease is recurrent, methicillin-resistant Staphylococcus aureus is suspected, treatment is ineffective, or the patient is at high risk. The Infectious Diseases Society of America recommends Gram stain and culture for impetigo and ecthyma but allows treatment without these tests in typical cases.[24]

NICE recommends reassessing a patient if symptoms rapidly or significantly worsen at any time or do not improve after completing a course of treatment. Reassessment should consider other diagnoses, signs of a more serious infection, such as cellulitis, and the possibility of bacterial resistance from previous antibiotic use. [25]

If recurrences occur frequently, it is advisable to send a swab from the lesion for microbiological testing, as well as examine a nasal swab. This helps identify carriage of Staphylococcus aureus, which may contribute to recurrent episodes in the patient or family members. [26]

Sometimes, a broader differential diagnosis is required for bullous rashes. Bullous impetigo must be distinguished from staphylococcal scalded skin syndrome, herpes simplex, chickenpox, burns, allergic contact dermatitis, drug reactions, toxic epidermal necrolysis, and autoimmune blistering diseases. [27]

Diagnostic step	When needed	What helps to understand
Skin examination	Almost always	Type of blisters, erosions and crusts
General condition assessment	Always	Is there a fever, weakness, complications?
Sowing of discharge	In case of relapse, treatment failure, or spread	Pathogen and sensitivity
Nasal swab	In case of frequent relapses	Carriage of Staphylococcus aureus
Contact evaluation	In children and in family cases	Source of infection
Revision of diagnosis	For atypical blisters	Exclusion of herpes, burns, drug reactions and other causes

Treatment

Treatment of bullous impetigo is aimed at eradicating Staphylococcus aureus, reducing infectivity, preventing the spread of lesions, and preventing complications. The choice of therapy depends on age, number of lesions, area of the lesion, general condition, location, risk of complications, and local resistance of the bacteria. [28]

For localized impetigo, topical antibiotics may be used. The Infectious Diseases Society of America recommends mupirocin or retapamulin twice daily for 5 days for bullous and nonbullous impetigo if a topical treatment route is chosen.[29]

If there are multiple lesions, the lesion is widespread, there is an outbreak in a community, the patient is immunocompromised, or local treatment is virtually impossible, oral antibacterial therapy is preferred. The MSD Manual also states that oral antibiotics are preferred for multiple lesions, immunocompromised patients, extensive disease, and outbreaks. [30]

NICE recommends taking local resistance data into account when prescribing an antimicrobial agent. UK guidelines for adults recommend 5-day regimens with fusidic acid 2% or mupirocin 2% for topical therapy, and flucloxacillin when oral therapy is required, with alternatives in cases of allergy or special circumstances; if methicillin-resistant Staphylococcus aureus is suspected, consultation with a microbiologist is recommended. [31]

Concurrently prescribing topical and oral antibiotics for the same episode without a specific reason is not recommended. This approach increases the drug burden and may exacerbate the problem of bacterial resistance, whereas in most cases, choosing a single, well-founded treatment option is sufficient. [32]

Situation	Possible tactics
Several small fires	Topical antibiotic as prescribed by a doctor
Multiple bubbles	Often an oral antibiotic is needed.
Outbreak in a family or group	Oral therapy may reduce transmission
Child under 1 year old	A particularly careful in-person assessment is needed
Suspected resistant staph	Sowing and specialist consultation
No improvement after the course	Re-examination, smear, revision of diagnosis
Ecthyma or deep lesion	Oral antibiotic, sometimes emergency treatment

Skin care at home

Home care doesn't replace antibiotics if needed, but it can help reduce the spread of infection. Blisters should be gently cleaned with water and a mild detergent, avoiding rubbing, picking at the blister caps, and avoiding picking at scabs until they bleed. [33]

After cleansing, it's best to cover open sores and areas that may come into contact with clothing or hands with a clean, dry bandage. This reduces the risk of transmitting bacteria to other people and reduces the risk of self-infection of new skin areas. [34]

Do not attempt to cauterize blisters with alcohol, iodine, hydrogen peroxide solution, harsh antiseptics, acids, or "drying" home remedies. Irritation damages the skin, can increase pain, and make it difficult to assess the true nature of the disease. [35]

It's important to keep your child's nails short and avoid touching the affected areas. If necessary, your doctor can provide recommendations for skin protection and itching control, especially if impetigo is caused by atopic dermatitis, insect bites, or another itchy condition. [36]

Towels, clothing, and bedding that have come into contact with the outbreaks should be kept separate and washed daily until the infection subsides. After washing, these items are safe for other family members to use, as long as normal hygiene measures are followed. [37]

Home measure	Why is it needed?	What to avoid
Gentle cleansing	Removes discharge and impurities	Strong friction
Closing of outbreaks	Reduces transmission of infection	Dirty or wet dressings
Washing hands	Reduces self-infection	Touching blisters without washing your hands
Short nails	Less scratching	Scratching until bleeding
Separate towels	Less household transmission	Sharing
Daily washing	Reduces bacteria on fabrics	Reusing soiled laundry

Differences from staphylococcal scalded skin syndrome

Bullous impetigo and staphylococcal scalded skin syndrome are both associated with toxigenic Staphylococcus aureus, but they are clinically distinct conditions. In bullous impetigo, the toxins act primarily locally at the site of infection, so blisters are often limited to specific areas of skin. [38]

In staphylococcal scalded skin syndrome, the toxin spreads through the bloodstream and causes extensive superficial peeling of the epidermis. The skin appears burn-like, with pain, widespread redness, fatigue, fever, large, fragile blisters, and areas of peeling skin. [39]

This distinction is crucial for management. Bullous impetigo can often be treated on an outpatient basis if it is limited and the patient feels well, whereas staphylococcal scalded skin syndrome is a dermatologic emergency requiring hospitalization, intravenous antibiotics, fluid management, and pain relief. [40]

Staphylococcal scalded skin syndrome is more common in children under 5 years of age than in adults due to an immature immune response and reduced ability to eliminate toxins. In adults, this condition is rare, but in those with immunodeficiency or severe renal failure, it can be particularly severe. [41]

If a child or adult has blisters that spread quickly, skin that is painful, red, peels easily when rubbed, fever, lethargy, or signs of dehydration, it does not look like regular localized impetigo and requires urgent medical attention.[42]

Sign	Bullous impetigo	Staphylococcal scalded skin syndrome
Prevalence	Usually local	Often extensive
Source of bubbles	The toxin acts at the site of infection	The toxin is distributed systemically
General condition	Often satisfactory, but fever is possible	Often fever, lethargy, pain
Leather	Isolated blisters and erosions	Extensive detachment, burn-like appearance
Treatment	Local or oral depending on severity	Hospitalization and intravenous antibiotics
Urgency	Depends on the severity	Emergency condition

Complications and warning signs

Most cases of bullous impetigo resolve without scarring if treated promptly because the infection is superficial. However, complications are possible, especially in infants, immunocompromised individuals, with widespread infection, delayed treatment, or improper care. [43]

Local complications include dissemination of infection within the skin, lymphangitis, lymphadenitis, cellulitis, bacteremia, and, less commonly, permanent scarring with deeper lesions. Queensland Health specifically emphasizes that complications are particularly important in bullous impetigo and ecthyma. [44]

Warning signs include rapid deterioration, high fever, lethargy, severe pain, hot, swollen skin around the lesion, red streaks from the affected area, pus, rapidly spreading blisters, and involvement of the area around the eyes. These symptoms require immediate in-person evaluation. [45]

NICE recommends referring patients with impetigo and signs of a more serious condition, such as cellulitis, to hospital, as well as those with widespread impetigo and immunocompromise. For bullous impetigo, particularly in children under 1 year of age, NICE recommends considering referral or specialist consultation. [46]

Rare delayed complications of streptococcal skin infections, such as post-streptococcal glomerulonephritis, are more often associated with Streptococcus pyogenes, while the bullous form is usually staphylococcal. However, if the diagnosis is mixed, there are multiple lesions, or edema, urine changes, and increased blood pressure occur after a skin infection, medical evaluation is necessary. [47]

An alarming sign	Possible meaning	What to do
Temperature and lethargy	Systemic reaction	See a doctor immediately
Rapid spread of bubbles	Possible complication or other diagnosis	Urgent assessment
Hot, swollen skin	Possible cellulite	Urgent inspection
Red streaks from the fire	Possible lymphangitis	See a doctor immediately
Lesions around the eyes	Risk of complications and diagnostic errors	Urgent consultation
Child under 1 year old	Higher risk	Consultation with a specialist
Immunodeficiency	Risk of severe course	Don't delay your appeal

Prevention of relapse and family infection

Prevention of bullous impetigo begins with contact monitoring and hygiene. Cover affected areas, wash hands after touching skin, use separate towels, wash linens and clothing, and avoid sharing razors, combs, washcloths, and personal care items. [48]

If impetigo recurs, it's important to look for the underlying cause. This could include carriage of Staphylococcus aureus, reinfection from a family member, atopic dermatitis, scabies, insect bites, poor wound healing, close contact in a group, or improper antibiotic use. [49]

In cases of frequent recurrences, NICE recommends sending a swab from the outbreak and examining a nasal swab, followed by carrier control measures. This helps avoid blindly prescribing the same antibiotic and increasing bacterial resistance. [50]

In children with atopic dermatitis or persistent itching, prevention is impossible without controlling the underlying skin condition. If the child continues to scratch, cracks and erosions regularly appear on the skin, making it easier for bacteria to gain a foothold and cause new episodes of impetigo. [51]

There is no need to use antibiotics "prophylactically" for every scratch or scab. NICE warns that prolonged or repeated use of topical fusidic acid and mupirocin increases the risk of antimicrobial resistance, so these drugs should be prescribed for short courses and as indicated. [52]

The purpose of prevention	What to do
Reduce gear	Cover the fires and wash your hands
Reduce household contamination	Separate towels and daily washing
Prevent self-infection	Don't touch the blisters, keep your nails short
Find the source of relapses	A smear from the lesion, sometimes a smear from the nose
Protect your skin	Treat dermatitis, itching, bites, cracks
Reduce stability	Do not use antibiotics without indications

FAQ

Is bullous impetigo contagious? Yes, it is a contagious bacterial skin infection. Bacteria can be transmitted through fluid from blisters, erosions, crusts, hands, towels, clothing, bedding, and personal care items. [53]

How does bullous impetigo differ from regular impetigo? In the bullous form, the main symptom is large superficial blisters, usually caused by toxigenic Staphylococcus aureus. In the non-bullous form, papules, pustules, and thick, "honey-colored" crusts are more common, and the causative agents can be Staphylococcus aureus, Streptococcus pyogenes, or both. [54]

Can blisters be popped at home? Popping blisters yourself is not recommended, as it increases the risk of spreading infection and causing further damage to the skin. It's best to cover the blisters with a clean bandage and consult a doctor for treatment. [55]

Are oral antibiotics always necessary? Not always, but in cases of multiple lesions, widespread infection, outbreaks, immunocompromised conditions, severe symptoms, or failure to respond to topical treatment, oral therapy is often preferred. For limited disease, the physician may choose topical treatment. [56]

Which antibiotic is used for bullous impetigo? The choice depends on the country, age, severity, local resistance, and risk of methicillin-resistant Staphylococcus aureus. Guidelines mention topical mupirocin or retapamulin, and for systemic therapy, drugs active against Staphylococcus aureus, such as dicloxacillin or cephalexin, as recommended by the Infectious Diseases Society of America. [57]

When can a child return to daycare or school? The U.S. Centers for Disease Control and Prevention recommends that a return should be no sooner than 12 hours after starting an appropriate antibiotic if the child is feeling well and the sores are closed; in some situations, 24 hours may be required. [58]

Is a smear necessary for bullous impetigo? In the typical mild case, the doctor may begin treatment without a smear, but a culture is useful in cases of relapse, widespread disease, treatment failure, an uncertain diagnosis, or suspected resistant bacteria. [59]

Can bullous impetigo progress to staphylococcal scalded skin syndrome? These are different clinical conditions, but both are associated with toxigenic strains of Staphylococcus aureus. If widespread redness, soreness, fever, lethargy, and large areas of peeling skin develop, this requires immediate medical attention. [60]

Does bullous impetigo leave scars? With prompt treatment, superficial impetigo usually heals without scarring. The risk of scarring is higher with deep lesions, ecthyma, severe secondary inflammation, skin trauma, or complicated progression. [61]

What should you do if impetigo recurs? You should see a doctor, have a swab of the lesion taken, have a nasal swab examined, check for possible carriage of Staphylococcus aureus, evaluate family sources of infection, and treat conditions that damage the skin, such as atopic dermatitis or scabies. [62]

Key points from experts

Dennis L. Stevens, MD, PhD, an infectious disease specialist, is one of the lead authors of the Infectious Diseases Society of America's skin and soft tissue infection guidelines. His key practice message for impetigo is that both bullous and nonbullous forms can be treated with topical or oral antimicrobials, but for multiple lesions and outbreaks, oral therapy is preferred to reduce transmission. [63]

Lawrence F. Eichenfield, MD, professor of dermatology and pediatrics at the University of California San Diego School of Medicine and chief of pediatric and adolescent dermatology at Rady Children's Hospital San Diego, has a clinical approach that is important for pediatric dermatology: in a child with a blistering rash, age, systemic condition, contagiousness, contact risks, atopic dermatitis, and the need for early treatment should be considered, rather than the blisters being treated as a "common irritation." [64]

Anthony J. Mancini, MD, professor of pediatrics and dermatology at Northwestern University Feinberg School of Medicine and chief of pediatric dermatology at the Ann and Robert H. Lurie Children's Hospital of Chicago, is particularly interested in bullous impetigo in children because the blistering rash requires differentiation from herpes simplex, burns, drug reactions, staphylococcal scalded skin syndrome, and rare bullous dermatoses. [65]

Asha C. Bowen, a professor of pediatric infectious diseases and a researcher of skin infections in children, emphasizes that impetigo is not only a localized skin problem but also an infection with high transmission in children, so treatment should combine antibiotic therapy, closure of lesions, hygiene, and prevention of reinfection. [66]

The authors of a Cochrane systematic review on the treatment of impetigo, including S. Koning et al., concluded that for limited impetigo, topical antibiotics such as mupirocin and fusidic acid have proven efficacy, but for widespread disease, bullous disease, flare-ups, or high risk of complications, the choice of therapy should be more cautious and clinically justified. [67]