Impetigo is a highly contagious bacterial infection of the surface layers of the skin, which causes sores and blisters (see Impetigo - symptoms).

Impetigo is not usually a serious condition. However, you should take precautions to avoid spreading it to other people, particularly newborn babies. For example, carefully wash your hands after touching affected areas of skin, and do not share towels or bed linen. See Impetigo - prevention for more information.

Treating impetigo

Antibiotic creams are usually recommended to treat the impetigo infection and minimise the risk of it spreading (see Impetigo - treatment).

Most people are no longer contagious after 48 hours of treatment, or once their sores have dried and healed.

As impetigo is a self-limiting condition (it gets better on its own), complications tend to be rare. However, sometimes the infection can spread to the lymph nodes (lymphadenitis), or to a deeper layer of skin (cellulitis). See Impetigo - complications for more information.

Types of impetigo

There are two types of impetigo:

• bullous impetigo - which causes large, painless, fluid-filled blisters
• non-bullous impetigo - which is more contagious than bullous impetigo and causes sores that quickly rupture (burst) to leave a yellow-brown crust

Impetigo can also be classed as:

• primary - where bacteria enters skin that is otherwise healthy - for example, through a cut or wound, or
• secondary - where the infection is the result of another underlying cause, such as atopic eczema (a common skin condition).

How common is impetigo?

Non-bullous impetigo is the most common type of impetigo, accounting for more than 70% of cases.

Impetigo most commonly affects children. This is due to environments, such as schools and nurseries, where the infection can easily be spread.

In the UK, around 3% of children up to four years old, and 2% of children who are between five to 14 years old get impetigo each year.

Impetigo can sometimes affect adults, for example, when people are living in a confined environment, such as an army barracks.

Impetigo does not cause any symptoms until four to 10 days after the initial exposure to the bacteria. This means that people can easily pass the infection on to others without realising that they are infected.

The symptoms of bullous and non-bullous impetigo are described below.

Bullous impetigo

The symptoms of bullous impetigo begin with the appearance of fluid-filled blisters, which usually occur on the trunk (the central part of the body from above the waist, but excluding the head and neck), or on the arms and legs.

The blisters may quickly spread, before bursting after several days to leave a yellow crust which heals without scarring.

The blisters are not usually painful, but the area of skin surrounding them may be itchy. As with non-bullous impetigo, it is important that you do not touch or scratch the affected areas of the skin.

Symptoms of fever and swollen glands are more common in cases of bullous impetigo.

Non-bullous impetigo

The symptoms of non-bullous impetigo begin with the appearance of red sores that usually occur around the nose and mouth. However, sometimes other areas of the face and the limbs can also be affected.

The sores quickly burst leaving thick, yellow-brown golden crusts. After the crusts dry, they leave a red mark that usually heals without scarring.

The sores are not painful, but they may be itchy. It is important not to touch, or scratch, the sores because this can spread the infection to other parts of your body, and to other people.

Other symptoms of an impetigo infection, such as a fever and swollen glands, are rare, although they may occur in more severe cases.

Ruling out other skin conditions

Impetigo is diagnosed based on the characteristics of your symptoms and by ruling out other skin conditions that have similar symptoms.

Some of the skin conditions that have similar symptoms to impetigo are listed below.

• Cellulitis: a bacterial infection of the deep layers of skin and tissue that lie underneath the skin.
• Erysipelas: a bacterial skin infection that usually affects the face or limbs.
• Herpes simplex virus: a highly contagious virus, also known as the ‘cold sore virus’, which can cause cold sores on the mouth and the genitals.
• Scabies: a contagious skin condition that causes intense itching.
• Ecthyma: a bacterial infection that affects the deep layers of the skin.
• Candidiasis: a fungal infection that causes redness of the skin and is common in areas such as the groin, under the arms, between the fingers, and between skin folds.
• Dermatophytosis: a skin infection with symptoms that can include red, scaly areas.
• Chickenpox: a highly infectious condition that causes an itchy rash that blisters and crusts over.
• Shingles: shingles is an infection of a nerve and the area of skin around it. Symptoms of shingles include tingling, pain and a blotchy red rash along one side of the body.

Other conditions that impetigo might be confused with impetigo include atopic eczema, contact dermatitis and insect bites. The symptoms of impetigo are also sometimes similar to those of burns and scalds.

Further testing

Further tests for impetigo are usually only required in cases where:

• the infection is severe and/or widespread
• the infection does not respond to treatment
• the infection keeps recurring (coming back)

In the above circumstances, a small area of affected skin will be gently wiped with a swab (like a large cotton bud) for testing.

The tests will help to rule out or confirm other skin conditions, such as those listed above, which may be responsible for your symptoms.

Complications of impetigo are rare, but they can occur and occasionally be serious. Tell your GP if your symptoms change or get worse.

Some of the complications of an impetigo infection are described below.

Cellulitis

Cellulitis occurs when the infection spreads to a deeper layer of skin. It can cause symptoms of red, inflamed skin, plus fever and pain. The condition can be treated with antibiotics, and paracetamol can be used to relieve pain.

See the A-Z topic about Cellulitis for more information.

Guttate psoriasis

Guttate psoriasis is a non-infectious skin condition that can develop in children and teenagers after a bacterial infection. It is usually more common after a throat infection, but some cases have been linked to impetigo.

Guttate psoriasis causes small (less than 1cm) droplet-shaped sores on the chest, arms, legs, and scalp. Creams can be used to control the symptoms of guttate psoriasis.

Scarlet fever

Scarlet fever is a rare bacterial infection that causes a fine, pink rash across the body. Associated symptoms of infection, such as nausea, pain and vomiting, are common. The condition is usually treated with antibiotics.

Scarlet fever is not usually serious but it is contagious. Therefore, it is important to isolate an infected child and avoid close physical contact. Keep your child away from school and other people until they have had at least five days of treatment with antibiotics.

See the A-Z topic about Scarlet fever for more information.

Septicaemia

Septicaemia is a bacterial infection of the blood. It can cause symptoms of:

• diarrhoea
• cold, clammy skin
• a high temperature (fever) of 38ºC (100.4ºF) or above
• rapid breathing
• vomiting
• low blood pressure (hypotension)
• confusion
• feeling faint and dizzy
• loosing consciousness

Septicaemia is a potentially life-threatening condition and requires immediate admission to hospital for treatment with antibiotics.

Post-streptococcal glomerulonephritis

Post-streptococcal glomerulonephritis is a very rare complication of impetigo. It is an infection of the small blood vessels in the kidneys.

The symptoms of post-streptococcal glomerulonephritis include:

• a change in the colour of your urine to a reddish-brown or cola colour
• swelling of the abdomen
• swelling of the face, eyes, feet and ankles
• a rise in blood pressure
• visible blood in the urine
• a decrease in the amount of urine you would normally produce

People with post-streptococcal glomerulonephritis will usually require immediate hospital treatment so that their blood pressure can be carefully monitored and controlled.

Post-streptococcal glomerulonephritis can be fatal in adults, although deaths in children are rare. Less than 1% of children die as a result of the condition.

As impetigo is a highly contagious condition, it is very important to take hygiene precautions to stop the infection spreading to other people.

The advice below will help to prevent the spread of infection.

• Keep children off nursery, playgroup or school until their sores have dried up, blistered, or crusted over, or until 48 hours after starting treatment.
• Do not share flannels, sheets or towels with infected people, and wash them at a high temperature after use.
• Wash the sores with soap and water, and cover them loosely with a gauze bandage or clothing.
• Do not touch the sores.
• Wash your hands frequently, particularly after touching infected skin.
• Avoid contact with newborn babies until the risk of contagion has passed (when the rash has crusted over, or after at least 48 hours of treatment with antibiotics).
• Washable toys should also be washed. Wipe non-washable soft toys thoroughly with a cloth that has been wrung out in detergent and warm water and allowed to dry completely.
• Treat suspected or confirmed cases quickly.
• Cover cuts and grazes with a plaster or dressing.

To prevent the impetigo returning, keep cuts and scratches clean, and ensure that any condition that causes broken skin, such as eczema, is treated promptly.