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Bacterial skin infections

Bacterial skin infections can conveniently be categorised according to the sites of infection – i.e. epidermal, dermal, follicular and other.


Impetigo is a common infection of the superficial layers of the skin, usually caused by Staphylococcus aureus and less commonly by Streptococcus pyogenes. Impetigo caused by methicillin-resistant Staphylococcus aureus is increasingly common. Impetigo most commonly affects young children. Risk factors include skin trauma or pre-existing skin disease (e.g. eczema, head lice or scabies), hot/humid weather, poor hygiene and crowded living conditions.

Impetigo can be bullous or non-bullous. Non-bullous impetigo accounts for about 70 per cent of cases. The characteristic lesions usually form around the nose and mouth, starting as small vesicles or pustules and quickly bursting to form yellow or brownish crusted, weeping plaques. Some textbooks describe this as “the golden crust”; others suggest the lesions look like “stuck-on cornflakes”. The infection can spread to other areas of the body (e.g. flexures, trunk and limbs).

The condition normally heals without scarring but it is contagious and often spreads rapidly in nurseries and playgroups. The fluid from the weeping lesions is highly infectious. The incubation period is four to 10 days. Children should be kept at home until scabs have formed over the lesions to minimise spread of infection.

Small areas of localised infection can be treated with topical fusidic acid, three times a day for five days. Larger areas require systemic treatment for seven days with oral flucloxacillin or clarithromycin.2 Suspected impetigo should be referred to a GP for antibiotic treatment unless the pharmacist is accredited to supply treatment under a patient group direction.

Good hygiene is important to prevent spreading the infection to other areas or passing it to other people. Towels, flannels and clothing should not be shared with others until the infection is over.

Patients (or carers) should be advised to complete the course of antibiotic treatment but not to carry on for longer. If there is no significant improvement after five days, or if the condition is rapidly worsening, then a consultation should be sought. Such patients may have impetigo caused by MRSA and need an alternative antibiotic, or may have developed a rare complication.