Also known as school sores
What is impetigo?
Impetigo is an infection of the skin that can be passed from person to person. It can affect skin that is intact (known as primary impetigo) or skin that is already compromised with cuts, abrasions, insect bites or other skin conditions such as eczema (known as secondary impetigo or impetiginisation). Generally, the condition affects younger children but any age group can be affected.
What causes impetigo?
Impetigo is caused by bacteria, most commonly Staphylococcus aureus (also known as ‘Staph’) and less commonly Group A Streptococcus (GAS). These germs can pass from person to person by skin to skin contact or by using the same towels or bedding.
Some factors such as hot humid weather, crowded living conditions, poor personal hygiene, an unhygienic work environment or a low or poorly functioning immune system can encourage the germs to infect the skin and cause impetigo.
Impetigo can spread rapidly through families and school classes but it can also appear as an isolated case.
What does impetigo look like?
In most people (about 70%), the rash starts with a red area which develops into small blisters filled with clear fluid or pus. The blisters join together and eventually break down leaving thick oozing crusts which have a characteristic golden yellow, honey colour known as “non-bullous impetigo”. This process usually takes about a week.
Much less commonly, particularly in young children, the small blisters join together to form large, loose, floppy blisters known as “bullae” known as “bullous impetigo”.
If the infection is deeper in the skin, an ulcer may form with a purplish colour around the outside and yellowish crust on top known as “ecthyma”.
What other problems can occur with impetigo?
Most cases of impetigo clear without any ongoing problems if the infection is treated early. As the patches clear up, the crusts tend to fall off and the areas usually heal without leaving scars. Temporary redness occurs in some cases.
Serious problems occurvery rarely. The bacteria can affect the deeper tissues of the skin causing “cellulitis”, the kidneys causing “post-streptococcal glomerunonephritis” or affect the heart. Most of these rare problems are caused by the germGroup A Streptococcus (GAS).
How is impetigo diagnosed?
The diagnosis is usually made by a doctor. Treatment is started immediately based on the typical appearance of the rash. A swab of the affected skin may be taken to determine which bacteria is the cause and before treating with antibiotics. A nose swab may also be taken to check for an underlying Staph infection.
How is impetigo treated?
This condition is treated with antibiotics.
Topical antibiotics are used if a small area of skin is affected. The crusts can be cleaned first with salty water (1 teaspoon of table salt is dissolved in a cup of hot water and left to cool) two to three times a day. Then a topical antibiotic such as topical mupiricin or fusidic acid is applied. Topicals antibiotics need to be used cautiously due to concerns of emerging resistance.
Oral antibiotics are often needed if large areas of skin are involved or there are multiple patches. Dicloxicillin or flucloxacillin are most commonly recommended. Other options include erythromycin, cephalexin or others depending on sensitivity of the particular offending bacteria. A full course (usually at least 7 days) should be completed.
Oral antibiotics are also needed if the rash has large blisters (bullous impetigo) or is “ecthyma”.
If Staph is grown from the nose swab, the nose will also need twice daily treatment with topical antibiotics (usually mupiricin) for 10 days.
Children should be kept home from school or day care until all the crusted and/or blistered areas have cleared.
If there is any other underlying skin condition, this should also be treated.
Good personal hygiene is important. Nails should be kept short and clean and affected people should wash their hands frequently with antibacterial soap and water or waterless antibacterial cleansers.
If the rash persists or you have any concerns, please see your dermatologist.
Further information about impetigo
This information has been written by Dr Sophie Bakis-Petsoglou
Updated 30 June 2015