What Is Impetigo? What Causes Impetigo?

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Main Category: Dermatology
Also Included In: Pediatrics / Children's Health;  Infectious Diseases / Bacteria / Viruses
Article Date: 04 Sep 2009 - 0:00 PDT

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Impetigo is a highly contagious skin infection that is most common in children, it is caused by the staphylococcus aureus, or more rarely streptococcus pyogenes bacteria. Children account for about 70% of all cases. The first sign of impetigo is a patch of red, itchy skin. In colder countries most cases of impetigo are caused by staphylococcus aureus, while in warmer countries the infection can be caused by both types of bacteria.

In northern Europe, northern USA and Canada impetigo is the most common childhood skin infection.

According to Medilexicon's medical dictionary, impetigo is " A contagious superficial pyoderma, caused by Staphylococcus aureus and/or group A streptococci, which begins with a superficial flaccid vesicle that ruptures and forms a yellowish crust; most commonly occurs in children."

There are two types of impetigo:

• Non-bullous impetigo (Impetigo contagiosa) - this causes sores that rapidly burst, leaving a yellow-brown crust. Non-bullous impetigo accounts for approximately 70% of all cases.


• Bullous impetigo - this causes large, painless, fluid-filled blisters.

Children aged between two and four years are the most likely to develop impetigo. However, people of all ages can be affected. Impetigo is more common where people live in confined environments, such as army barracks.

Impetigo is rarely serious and usually resolves on its own within a couple of weeks. However, doctors may decide to treat children with an antibiotic ointment or oral antibiotics to prevent complications, which may sometimes occur.

What are the symptoms of impetigo?

Non-bullous impetigo (Impetigo contagiosa)

Red sores appear, generally around the mouth and nose. The sores soon burst and ooze either fluid or pus, leaving thick, yellowish-brownish golden crusts. As the crusts dry they leave a red mark which usually heals without any scarring.

Although the sores are not painful they may itch a great deal. It is important not to touch or scratch them, so that the infection does not spread to other parts of the body and other people.

In rare cases symptoms may be more severe and the patient may have a fever and swollen glands.

Bullous impetigo

This type mainly affects babies and children under the age of two.

Fluid-filled blisters appear, generally on the trunk, legs and arms. The skin around the blister is generally red and itchy, but not sore. They often spread rapidly and eventually burst, leaving a yellow crust. The crust eventually heals with no scarring.

Although the blisters are not painful they may itch a lot. Patients must try not to touch or scratch them.

Fever and swollen glands are more common in patients with bullous impetigo.

What causes impetigo?

Impetigo is caused by two types of bacteria:

• Staphylococcus aureus
• Streptococcus pyogenes

Both types of bacteria exist harmlessly on human skin. They cause infection when there is a cut or wound. Impetigo in adults is usually the result of injury to the skin - commonly by another skin condition, such as dermatitis (inflammation of the skin). Children are usually infected after a cut, scrape or insect bite. However, children may also become infected without any apparent skin damage.

One person can become infected by touching things that an infected person has been in contact with, such as bed linen, towels, toys, and clothing. Once infected, that person can easily pass it on to other people.

Staphylococcus aureus produces a toxin that causes impetigo to spread to nearby skin. The toxin attacks a protein that helps keep skin cells bound together. As soon as this protein is damaged, the bacteria spread rapidly.

There are two ways the infection can start:

• Primary impetigo - the bacteria invade the skin through a cut, insect bite, or other lesion.


• Secondary impetigo - bacteria invade the skin because another skin infection/condition has disrupted the skin barrier, such as eczema or scabies.

Symptoms do not appear until four to ten days after initial exposure to the bacteria. During those days people can pass the infection on to others, and tend to do so because they do not know they are infected.

Experts say children are more likely to become infected and show symptoms because their immune systems are not yet fully developed.

How is impetigo diagnosed?

Impetigo is fairly easy to diagnose and a GP (general practitioner, primary care physician) will do so after examining the affected area. The doctor will probably ask the patient (or parent) about any recent cuts, scrapes or insect bites to the affected area. The doctor will also try to find out whether it has come up on top of another skin condition, such as scabies.

Further tests may be ordered if:

• Symptoms are very severe and have spread to many parts of the body.
• The patient does not respond to treatment.
• The infection keeps recurring.

The doctor will gently wipe a crusted area with a swab to see which germ is causing the impetigo and which antibiotic is most likely to help. A swab may also help determine whether another infection is present, such as ringworm or shingles.

If the patient is getting recurrent episodes of impetigo the doctor may take a swab from the nose to determine whether the infective bacteria is harboring there.

What are the treatment options for impetigo?

The aim of treatment is to speed up healing, improve the skin's appearance and prevent complications and the spread of infection. Treatment will depend on the type of impetigo and the severity of symptoms.

• Mild infections - a doctor may opt for just hygienic measures. This means keeping the skin clean.


• Topical antibiotics - antibiotics which are applied directly onto the skin. The doctor may prescribe mupirocin ointment (Bactroban). Before applying the ointment scabs need to be gently removed so that the antibiotic can get deep into the skin.
  
  It is important to first wash affected areas of skin with warm, soapy water before applying the topical antibiotic. If possible, use latex gloves when applying the cream. Afterwards wash your hands thoroughly. The patient should respond to treatment within seven days.


• Oral antibiotics - these are swallowed and are prescribed when the impetigo is more widespread or if the patient has not responded to topical antibiotics. The type of antibiotic depends on the severity and type of infection, as well as other factors, such as the patient's medical condition and whether he/she has any allergies.
  
  A course of antibiotics usually lasts about 7 days. It is important to complete the course, even if symptoms clear up early.
  
  Antibiotics may have the following side effects, which usually disappear within a few days:
  • Stomachache
  • Nausea
  • Diarrhea
  • Yeast infections, such as thrush (in women)

A child can go back to school 48 hours after antibiotic treatment started, or when the sores have crusted and healed.

Complications of impetigo

On the very rare occasions that complications do occur, they can be serious. Any parent who sees worsening symptoms in their child should tell their doctor straight away.

• Cellulitis - when the infection goes into a deeper layer of skin cellulitis can occur, and can cause symptoms of red inflamed skin, fever and pain. The patient will need antibiotics and sometimes painkillers.


• Guttate psoriasis - this type of psoriases is characterized by red, scaly patches of inflamed skin on all parts of the body. It is a non-infectious skin condition which may occur in children and teenagers after a bacterial infection, especially a throat infection. Sometimes it can occur after impetigo.


• Scarlet fever - also called scarlatina. It is a rare bacterial infection characterized by a fine pink rash across the body. The patient may also have nausea, vomiting and pain. Treatment includes antibiotic. It is not serious but is contagious.


• Septicemia - bacterial infection of the blood. The patient will have a fever, possibly rapid breathing and vomiting, confusion and dizziness. This is a life-threatening infection and requires immediate hospitalization.


• Post-streptococcal glomerulonephritis - an infection of the small blood vessels in the kidneys which can be fatal for adults. This complication of impetigo is very rare. Symptoms include darkened colored urine and hypertension. Patients will usually have to be hospitalized so that their blood pressure can be monitored.

Prevention of impetigo

Good hygiene is the best way to reduce the risk of developing or spreading impetigo. Cuts, scrapes, grazes, and insect bites should be washed immediately and kept clean. If somebody has impetigo it is important to keep their belongings isolated from other people, and to follow strict hygiene measures.

The following will help prevent the spread of infection to others, and also to other parts of the patient's body:

• Wash the affected areas with a neutral soap and running water.
• Then cover the area lightly with gauze.
• Do not touch the sores. Encourage the patient not to touch the sores.
• The patient's clothes, bedding, towels and other toiletries should be washed daily.
• The patient's clothes must not be shared or worn by other people.
• When applying antibiotic ointment wear gloves, and wash hands thoroughly afterwards.
• Keep the patient's nails short to reduce scratching.
• Wash your hands and the patient's hands often.
• Isolate the patient until you are sure he/she is not contagious.

To prevent a recurrence of impetigo make sure any skin condition, such as eczema, is treated properly.

Written by Christian Nordqvist


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