Impetigo

Introduction | Aetiology and Risk Factors | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | References

Introduction

Impetigo is a highly contagious bacterial skin infection that commonly affects infants and young children, but it can occur at any age. It typically presents as red sores on the face, particularly around the nose and mouth, and on the hands and feet. The sores burst, develop honey-coloured crusts, and can spread to other parts of the body or to other individuals through direct contact or sharing of items such as towels or toys.

Aetiology and Risk Factors

Impetigo is caused by bacteria, most commonly Staphylococcus aureus and, less frequently, Streptococcus pyogenes (Group A Streptococcus):

• Types of Impetigo:
  • Non-Bullous Impetigo: The most common form, characterised by small vesicles that rupture and form honey-coloured crusts.
  • Bullous Impetigo: Less common, caused by strains of Staphylococcus aureus that produce exfoliative toxins. It presents with larger blisters that can rupture, leaving raw skin underneath.
• Risk Factors:
  • Age: Most common in children, particularly those aged 2 to 5 years.
  • Close Contact: Living in crowded conditions or close contact with an infected person increases the risk of transmission.
  • Skin Trauma: Minor skin injuries, such as cuts, insect bites, or dermatitis, can predispose to impetigo.
  • Poor Hygiene: Lack of regular handwashing or cleaning of skin can contribute to the spread of infection.
  • Warm, Humid Climate: Impetigo is more common in warm, humid environments.

Clinical Presentation

Impetigo presents with the following signs and symptoms, varying slightly between the non-bullous and bullous forms:

• Non-Bullous Impetigo:
  • Begins as small red spots or papules, typically on the face, especially around the nose and mouth.
  • The spots quickly develop into vesicles or pustules that rupture, leaving honey-coloured crusts.
  • Lesions can spread to other parts of the body through scratching or direct contact.
  • Itching is common, but pain is usually minimal.
• Bullous Impetigo:
  • Presents with larger blisters (bullae) filled with yellow or clear fluid, primarily on the trunk, arms, or legs.
  • The bullae eventually rupture, leaving red, raw skin underneath, which may develop a brown crust.
  • This form is more likely to affect neonates and young children.
• Systemic Symptoms: Generally, systemic symptoms such as fever are rare but may occur in more severe cases or if secondary infections develop.

Diagnosis

The diagnosis of impetigo is primarily clinical, based on the characteristic appearance of the lesions:

• Clinical Examination: The presence of honey-coloured crusts on erythematous bases is typically diagnostic of non-bullous impetigo.
• Bacterial Swab: A swab of the affected area may be taken for culture and sensitivity testing, particularly in recurrent cases, to guide antibiotic therapy.
• Differential Diagnosis: Consider other conditions that may present similarly, such as herpes simplex, eczema herpeticum, or contact dermatitis.

Management and Treatment

Management of impetigo focuses on eliminating the infection, preventing its spread, and alleviating symptoms:

1. Topical Antibiotics

• Fusidic Acid Cream: Applied three times daily to the affected area, fusidic acid is effective for mild to moderate cases of non-bullous impetigo.
• Mupirocin 2% Ointment: Another topical antibiotic option, particularly useful for localized infections. Applied three times daily for 5-7 days.

2. Oral Antibiotics

• Flucloxacillin: The first-line oral antibiotic for more extensive or bullous impetigo. It is effective against Staphylococcus aureus and Streptococcus pyogenes. Typically prescribed for 7 days.
• Erythromycin or Clarithromycin: Alternatives for patients allergic to penicillin.

3. Supportive Care

• Hygiene Measures: Encourage regular handwashing and keeping nails short to prevent the spread of infection. Avoid sharing towels, bedding, or clothing with others until the infection is cleared.
• Skin Care: Gently clean the affected area with soap and water before applying topical antibiotics.
• Itch Relief: Oral antihistamines may help alleviate itching, particularly at night.

Prevention

Preventive measures can reduce the risk of impetigo and limit its spread:

• Avoid Close Contact: Avoid close contact with infected individuals and sharing personal items such as towels, clothing, or toys.
• Good Hygiene Practices: Regular handwashing and maintaining good personal hygiene are crucial in preventing impetigo, especially in children.
• Wound Care: Properly clean and cover any cuts, scratches, or insect bites to reduce the risk of developing impetigo.

When to Refer

Referral to a specialist may be necessary in the following situations:

• Severe or Recurrent Cases: If impetigo is severe, recurrent, or does not respond to initial treatment, referral to a dermatologist or paediatrician may be required.
• Suspected Complications: If there are signs of complications such as cellulitis, post-streptococcal glomerulonephritis, or systemic symptoms, referral is recommended.
• Uncertain Diagnosis: If the diagnosis is unclear or if the presentation is atypical, a specialist referral may be necessary for further evaluation and management.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Impetigo. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Impetigo: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng105 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical and Systemic Treatments for Skin Infections. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).