Impetigo

Dr Haran Sivapalan
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What is Impetigo?

Impetigo is a common infection of the upper layers of the skin. It tends to affect children, although can affect people of any age. It is caused by bacteria, and the bacterial infection gives rise to red sores and fluid-filled blisters on the skin which can then crust over and may be itchy.

Depending on the type of impetigo the blisters may occur on the face, usually around the mouth or nose, or the body, including the legs, arms, trunk and buttocks.

It is contagious and can be spread from person to person by touch or by sharing things like towels or bedding. If you have impetigo, you can do certain things to minimise the risk of passing it on to others, trying not to scratch them, including regularly handwashing, not sharing baths, bedding or towels, and staying away from school or day care for 48 hours after starting antibioitic treatment.

There are two main types: bullous and non-bullous. Non-bullous impetigo is more common and causes smaller blisters that quickly burst forming a yellow crust on the skin. Bullous impetigo is less common and characterised by larger, fluid-filled blisters.

Each year, it affects 2.8% of children under the age of 4 and 1.6% of children aged between 5 and 15.

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The symptoms of impetigo include red sores, blisters and crusting of the skin. The exact symptoms depend on the type of the impetigo you have.

Non-bullous impetigo

Non-bullous impetigo is the most common form of impetigo.

Non-bullous impetigo usually begins with small, red sores or blisters that form about 4-10 days after infection with the bacteria. The blisters typically affect the skin around the nose and mouth. It may not be possible to see the blisters because they soon burst, giving rise to golden or honey-colour crusts. The crusts are usually under 2cm in diameter and are sometimes said to have the appearance of ‘cornflakes stuck to the skin.’

Other smaller patches of impetigo may arise around a main patch of impetigo. These are known as ‘satellite’ patches.

Patches of impetigo may be itchy. Lymph nodes around the face may sometimes swell up to fight the infection.

Bullous impetigo

Bullous impetigo produces larger fluid-filled blisters (bullae) on the skin. Blisters are normally about 1-2cm in diameter. The fluid inside the blisters is often clear or yellow initially and may turn dark or cloudy over time.

The skin on top of the blisters is very thin and the blisters usually burst spontaneously after several days. This then leaves areas of raw, red skin below. Normally the skin then heals without scarring.

Blisters may affect the face, arms, legs, trunk and buttocks.

Impetigo is caused by bacteria infecting the skin. The two main bacteria responsible for impetigo are: Staphylococcus aureus and Streptococcus pyogenes. MRSA (methicillin-resistant staphylococcus aureus), a type of bacteria that is resistant to several antibiotics, is also known to cause impetigo.

Breaks in healthy skin (e.g. through a cut, wound or abrasion) allow the bacteria to enter the skin and cause an infection. This is known as primary impetigo.

Alternatively, another skin condition such as eczema or psoriasis may facilitate the entry of bacteria into the skin and allow infection. This is known as secondary impetigo. Other conditions that increase the risk of secondary impetigo include: chickenpox, contact dermatitis and scabies.

A GP can usually diagnose impetigo based on the appearance of the skin. Further investigations are rarely required.

Swabs of the skin may be taken to help the doctor confirm the bacteria causing the infection, allowing them to prescribe the appropriate antibiotic. This procedure is more likely if MRSA is suspected as the cause of impetigo.

Antibiotics are the mainstay of treatment for impetigo. They work by destroying the bacteria that have infected the skin. Topical antibiotics applied to the skin are used for localised patches of non-bullous impetigo. Bullous impetigo and more widespread or more severe non-bullous impetigo generally require treatment with oral antibiotics.

Most cases of impetigo will resolve spontaneously over 2-3 weeks. Treatment is nevertheless recommended in order to shorten the duration of illness and to prevent the spread of the infection to others.

Topical antibiotics

Topical antibiotics include creams such as fusidic acid, mupirocin and retapamulin. Fusidic acid cream is the most commonly used antibiotic and is applied to the skin 3-4 times a day for about 7 days.

Before the cream is applied, it is important to clean off any crusts with warm, soapy water. This allows the antibiotics to more easily penetrate the skin.

Side effects of topical antibiotics include itching, redness and irritation of the skin.

Oral antibiotics

Antibiotic tablets, capsules or liquids (oral antibiotics) are taken for bullous impetigo as well as more severe and widespread cases of non-bullous impetigo. Flucloxacillin is usually used and is taken 4 times a day for a week. Other commonly-used antibiotics include clarithromycin and erythromycin.

Side effects of oral antibiotics include nausea and diarrhoea.

Impetigo is contagious and can be spread from person to person by touch. If you have impetigo, you can do certain things to minimise the risk of passing it on to others.

  • Wash your hands after touching the affected area of skin.
  • Wash your hands after applying topical antibiotics.
  • Avoid scratching the area – you might find it helpful to keep your fingernails short.
  • Avoid sharing towels, bathwater and bed linen
  • Avoid school or work until 48 hours after antibiotic treatment has started or until the patches have dried and scabbed over.

Impetigo. NICE CKS (2015). Available online at: https://cks.nice.org.uk/impetigo

Impetigo. Patient.info (2016). Available online at: http://patient.info/health/impetigo-leaflet

Impetigo – Professional Reference Article. Patient.info (2016). Available online at: http://patient.info/doctor/impetigo-pro

Impetigo. NHS Choices (2016). Available online at: http://www.nhs.uk/Conditions/Impetigo/Pages/Introduction.aspx