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Impetigo

Impetigo is a skin infection caused by the bacterium Staphylococcus aureus or Streptococcus pyogenes.

Impetigo causes spots containing pus (pustules) that become crusty yellow sores. It often occurs on the face around the mouth and nose. It can be treated with antibiotic creams or tablets.

  • About impetigo
  • Symptoms
  • Complications
  • Causes
  • Diagnosis
  • Treatment
  • Prevention
  • Further information
  • Sources
  • Related topics

About impetigo

Impetigo is highly contagious and easily spreads from person to person by touch.

Impetigo is thought to be most common between the ages of two and six. About one in 35 children under the age of four and one in 60 children under 15 develop impetigo. In a survey of Dutch children it was the third most frequent skin condition, after eczema and viral warts. It's thought to be more common in tropical and developing countries.

Symptoms

Impetigo infection begins with the development of small pustules. These usually appear on your face around the nose or mouth, although they can occur anywhere - for example your arms and legs when cuts get infected.

The pustules burst quickly, and then crust over and turn yellow. More pustules may develop in surrounding areas of skin. The crusts eventually dry out and heal to leave a red mark, which gradually disappears without scarring.

Impetigo can sometimes be painful or itchy, but you don't usually get other symptoms such as a fever or feeling ill. You may develop swollen lymph nodes (glands throughout your body that make up part of the immune system), especially near the affected area.

There are two types of impetigo. Bullous impetigo causes larger fluid filled blisters to develop which don't burst easily and tend to last for a few days. It's more common on the trunk (chest, back and abdominal area). Non-bullous impetigo is more common on the face or limbs and causes smaller, less persistent pustules.

Complications

There are usually no serious complications with impetigo, but it can spread to other areas of the body or other people. You are more likely to have complications if you have bullous impetigo.

Rarely, the infection can spread beyond the skin and bacteria get into the blood stream. This is called septicaemia, or blood poisoning. It needs emergency medical treatment. Sometimes impetigo spreads to the lower layers of the skin, causing a condition called cellulitis. This causes redness and swelling.

Occasionally impetigo leads to a type of kidney problem called glomerulonephritis. Impetigo may cause scarlet fever, an illness which causes a sore throat, fever and reddened skin.

Impetigo infection can also lead to psoriasis - a type of skin condition that causes dry scaly patches on the skin.

Impetigo is usually straightforward to treat (See Treatment).

Causes

In moderate climates impetigo is most commonly caused by the bacterium Staphylococcus aureus. However, in warmer, moister climates it is more likely to be caused by the bacterium Streptococcus pyogenes. It may also be caused by a combination of both bacteria.

Impetigo is highly contagious. This means it can spread to other people very easily. This can happen either through direct skin to skin contact, or from sharing towels or face flannels.

Impetigo usually develops between four and 10 days after you are first exposed to it. If it develops in healthy skin it is called primary impetigo.

Sometimes impetigo starts in an area of broken skin. For example, at the site of a wound, or an area affected by another condition that breaks the skin, such as eczema or scabies. This is called secondary impetigo.

You are also more likely to develop impetigo if you have:

  • poor personal hygiene
  • diabetes mellitus
  • a weakened immune system, for example if you have HIV/AIDS or cancer

Diagnosis

If you think you or your child has impetigo you should see your GP. It's usually straightforward to diagnose from the typical look of the affected skin.

However, impetigo can sometimes be confused with other skin conditions such as shingles, fungal skin infections or cold sores. If there is any doubt, your doctor might take a swab from the affected area. The swab will be tested at a laboratory.

Treatment

Impetigo can usually be treated with a course of antibiotics. Your GP will probably prescribe fusidic acid, but there are other antibiotics that can be used. Fusidic acid is an available as an ointment or a cream. You apply it to the affected area three to four times a day. This will clear up most impetigo infections in seven to 10 days.

You will need to wash the affected area with warm soapy water to remove crusty areas before applying the cream or ointment.

Sometimes an impetigo infection may be more persistent or widespread. If applying cream or ointment doesn't work you may be given antibiotic tablets such as flucloxacillin or erythromycin. If the infection keeps coming back the bacteria responsible may be living in your nose. Your doctor may prescribe a nasal ointment to try to clear the bacteria from this area.

Always ask your doctor for advice and make sure you read the patient information leaflet that comes with your medicine.

Prevention

Impetigo is highly contagious, so it's important to take steps to stop it spreading between family members and other people you come into contact with.

  • If your child has impetigo, don't send him or her to school or nursery until treatment is finished and the area is no longer weeping.
  • Don't share towels or flannels.
  • Don't share soap.
  • Don't touch the pustules.
  • Wash your hands if you do touch the pustules.
  • Don't scratch the affected area and keep your fingernails short.

 Further information

British Association of Dermatologists

Sources

  • Simon C, Everitt H, and Kendrick T, Oxford handbook of general practice. 2nd ed. Oxford: Oxford University Press, 2005: 332, 668
  • Koning S, Verhagen AP, van Suijlekom-Smit LWA, et al. Interventions for impetigo. Cochrane Database of Systematic Reviews 2003, Issue 2
  • Treatments for impetigo. Bandolier. www.jr2.ox.ac.uk/bandolier/, accessed 23 October 2007
  • Impetigo. Clinical knowledge summaries. www.cks.library.nhs.uk, accessed 23 October 2007
  • Impetigo. Health Protection Agency North West. www.hpa.org.uk, accessed 23 October 2007
  • British National Formulary (BNF). BMJ Publishing Group, 2007. 53: 620

Related topics

  • Psoriasis
  • Shingles
  • Eczema