Impetigo is a common infection of the skin. It is contagious, which means it can be passed on by touching. Most cases occur in children but it can affect anybody of any age. Antibiotic cream usually clears the infection quickly. Antibiotic tablets or liquid medicines are sometimes needed.
What is impetigo and what does it look like?
Impetigo is a skin infection. It is usually caused by a germ (bacterium). It is usually caused by one of the following three types of bacteria:
- Staphylococcus aureus (the most common cause).
- Streptococcus pyogenes.
- Meticillin-resistant Staphylococcus aureus (MRSA). This is a newer type of bacterium which has become resistant to many antibiotics.
Impetigo may be classed as primary or secondary:
- In primary impetigo, the infection affects healthy skin.
- In secondary impetigo, the infection affects skin that is already 'broken' by another skin condition. For example, skin with eczema, psoriasis or a cut sometimes develops a secondary impetigo.
It can also be classed as bullous type, non-bullous type or ecthyma.
This is the most common type. The rash typically appears 4-10 days after you have been infected with bacteria. Small blisters develop at first. You may not see the blisters, as they usually burst to leave scabby patches on the skin. Sometimes only one or two patches develop. They often look like moist, golden crusts (like cornflakes) stuck on to the skin. An area of redness (inflammation) may develop under each patch. Sometimes affected skin is just red and inflamed - especially if the 'crust' is picked or scratched off.
The face is the most common area affected but impetigo can occur on any part of the skin. Patches of impetigo vary in size but are usually quite small - a centimetre or so to begin with. Smaller 'satellite' patches may develop around an existing patch and spread outwards.
This type of impetigo tends to look like larger blisters. The skin on the top of these blisters is very thin and peels off, leaving large red raw areas underneath. It may occur on your face, arms, legs, or bottom. It is more likely in areas which already have another skin condition, such as eczema.
This is a more uncommon type of impetigo where the breaks in the skin are quite deep, forming ulcers.
Who gets impetigo?
Impetigo commonly occurs in children, but it can affect anyone at any age. It occurs more commonly in hot humid weather. It is contagious, which means it can be passed on by touching. Sometimes outbreaks occur in families or in people who live in close communities, such as army barracks.
You are more prone to develop impetigo if you have diabetes or if you have a poor immune system (for example, if you are having chemotherapy).
What is the treatment for impetigo?
There is a good chance that impetigo will clear without treatment after 2-3 weeks. However, treatment is usually advised as it is contagious, and severe infection sometimes develops.
A medication, in the form of an antibiotic cream used for seven days, is the usual treatment for a few small patches of impetigo on the skin. The usual treatment of choice is topical fusidic acid. Alternatives are mupirocin cream or retapamulin cream. If it is not too sore, the crusts should be cleaned off with warm soapy water before the cream is applied. This allows the antibiotic to penetrate into the skin.
Antibiotic liquid medicine or tablets may be prescribed in some situations. This may be needed if, for example:
- The rash is more widespread.
- The infection is spreading, despite using the cream.
- The infection has come back despite treatment.
- You have a poor immune system.
- You are generally unwell with symptoms such as high temperature (fever) and swollen lymph glands.
In such cases, the treatment of choice is oral flucloxacillin for seven days. However, if you are allergic to penicillin, the recommended alternative is oral clarithromycin for the same length of time.
Avoiding passing impetigo on to others
As impetigo is contagious (ie, it can be passed on by touching):
- Try not to touch patches of impetigo and do not allow other children to touch them.
- Wash your hands after touching a patch of impetigo and after applying antibiotic cream.
- Don't share towels, flannels, bathwater, etc, until the infection has gone.
- Children should be kept off school or nursery until there is no more blistering or crusting, or until 48 hours after antibiotic treatment has been started.
- Adults with impetigo should also stay off work until crusts have dried and scabbed over, or until 48 hours after antibiotics have been started.
Some uncommon aspects of impetigo
If treatment does not work
Tell your doctor if the initial treatment does not work. A possible cause for this is if the germ (bacterium) causing the infection is resistant to the prescribed cream or tablet. A switch to a different antibiotic is sometimes needed if the first does not work. Sometimes your doctor will take a swab to see which germ is causing the infection. A swab is a small ball of cotton wool on the end of a stick which is used to obtain mucus and cells. This sample is examined under a microscope in a laboratory. The result will help guide the best choice of treatment.
If your impetigo returns (recurs)
It is common for children to have one or two bouts of impetigo at some stage. However, some people have recurring bouts of impetigo. A possible cause for this is that the bacteria that cause the infection can sometimes live in ('colonise') the nose. They do no harm there but sometimes spread out and multiply on the face to cause impetigo. If this is suspected, your doctor may take a swab of the nose. The swab is then sent to the laboratory to look for certain colonising bacteria. If necessary, a course of antibiotic cream applied to the area just inside the nose can clear these bacteria. The cream most often used in these cases is called Naseptin®.
Some things to look out for
Another skin infection called cellulitis is sometimes mistaken for impetigo. Cellulitis is a 'deeper' skin infection. Normally, with cellulitis the area of skin affected is larger, the skin is red, swollen and tender and there are not usually any blisters or crusts. Cellulitis usually needs prompt treatment. See the separate leaflet called Cellulitis and Erysipelas for more details. In particular, see a doctor urgently if cellulitis develops close to an eye.
A patch of impetigo on the face near to the mouth is sometimes confused with a cold sore. Cold sores are due to a viral infection and tend to recur in the same place from time to time. See the separate leaflet called Cold Sores for more details.
Further reading and references
; NICE CKS, July 2015 (UK access only)
; Interventions for impetigo. Cochrane Database Syst Rev. 2012 Jan 181:CD003261. doi: 10.1002/14651858.CD003261.pub3.
; DermNet NZ
; Primary Care Dermatology Society (PCDS)
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