Concise guide: Impetigo

Impetigo is a highly contagious bacterial skin infection that primarily affects children, usually on the face, but can also occur in adults.

Impetigo presents in two primary forms: 
• Non-bullous impetigo 
• Bullous impetigo.

Non-bullous impetigo is more common, accounting for around 70 per cent of cases. Lesions begin as red sores that quickly rupture, releasing exudate and leaving behind a honey-coloured or golden-brown crust. 

Bullous impetigo is characterised by large, fluid-filled blisters that rupture, resulting in the same characteristic crust.

Causes and transmission

Impetigo is usually caused by Staphylococcus aureus bacteria. Streptococcus pyogenes can also cause impetigo, albeit less frequently. The infection typically enters the body through small breaks in the skin, such as those arising from insect bites, cuts or scratches, or underlying skin conditions such as eczema, scabies or chickenpox. 

Symptoms

Common symptoms of impetigo include red sores that quickly burst and ooze, forming a characteristic golden crust. These sores are usually itchy and can appear on the face, around the nose and mouth, as well as on the hands and feet.  

In bullous impetigo, larger fluid-filled blisters (more than 5mm in diameter) may be present, surrounded by red skin. Once the crusts of both types of impetigo have dried, they separate leaving redness, which then fades over a two or three-week period.

Diagnosis

Diagnosing impetigo is often based on clinical appearance. The distinctive appearance of the sores and crusts is usually sufficient for diagnosis. However, in some cases, a swab of the affected area is taken and sent for laboratory testing to confirm the presence of bacteria.

Minimising spread and prevention

Regular hand washing with soap and water should be encouraged, especially after touching the affected areas. Patients should avoid sharing personal items and clothing. Wounds or cuts should be kept clean and covered.

Antibacterial preparations may help. The British Association of Dermatologists recommends that children with impetigo should be kept off school until the affected areas have healed or 48 hours after starting treatment.

Impetigo’s characteristic sores and crusts can be mistaken for other skin conditions, such as eczema, cold sores and even insect bites. Differentiating factors include the presence of golden crusts, and its rapid onset and contagious nature.

Treatment

NICE recommends that hydrogen peroxide 1% cream can be used in children with non-bullous impetigo. Alternatively, a short course (five to seven days) of a topical prescription-only antibiotic (e.g. fusidic acid 2% or mupirocin 2% where fusidic acid resistance is suspected) can be applied. 

Oral antibiotics such as flucloxacillin or clarithromycin may be used if topical treatments don’t work, or the impetigo is bullous or affecting several sites.

Hygiene advice

In more severe cases or if the infection is spreading, oral antibiotics may be necessary. As with any antibiotics, patients must complete the entire course even if the symptoms improve before the medication is finished. Emphasise the importance of maintaining good hygiene practices to prevent recurrence or further spread.

Complications

When impetigo is left untreated or improperly managed, complications can arise. These may include the spread of the infection to other parts of the body, such as lymph nodes, or the development of cellulitis (an infection deeper in the skin). Educate patients about the potential risks and the importance of seeking medical attention if their symptoms worsen.

When to refer 

Refer patients to a doctor in the following situations:
• Bullous impetigo, particularly in babies under one year
• The infection recurs frequently or doesn’t improve with treatment
• The patient has a fever, indicating a more severe infection, or is systemically unwell, suggesting possible sepsis
• The infection is spreading rapidly
• The tissue around the infected area is swollen, suggesting cellulitis
• The patient is a young child, an elderly individual, or has a weakened immune system or a high risk of complications.