What is Impetigo?

By Dr Liji Thomas, MD

Impetigo is a very contagious bacterial skin infection that causes skin sores. It is mostly due to staphylococci, but is also caused by streptococci, entering through a break in the skin. The skin may be broken by a scratch or cut, or by allergic ulcers, sores or infestations.

It is most often seen in young children, between 2 and 6 years. The first sign of impetigo occurs 4 to 10 days after infection, even though it can spread from one person to another before that.

Patients show a small red sore, like a pimple, most commonly on the face, arms, or legs. They become purulent, and then ooze pus, usually within a few days, which covers them with thick yellow crust. As the crust contracts, the skin itches, leading to spread of the bacteria as a result of scratching. It usually heals within a week of the start of treatment, without complications. The healing sores leave behind light reddish scars, which gradually fade with time.

You need to consult your doctor if there is any sign of deeper infection. Impetigo in newborns can be dangerous, and requires prompt antibiotic treatment.

Impetigo can manifest in two ways.

Bullous impetigo

This type is most commonly seen in babies. It erupts as fluid-filled blisters on the trunk, most often, which break open quickly, to appear as a yellowish crust.

Non-bullous impetigo

This makes up about 70% of all cases of impetigo. It occurs mostly around the nose and mouth, as sores which quickly crust over to a dirty yellow color.

Diagnosis and treatment

Diagnosis is made on clinical grounds. Treatment is with antibiotic pills or creams. The sores should be washed twice a day. An airtight dressing should be applied if the child goes out, to prevent spread of infection. After about 48 hours of treatment, the sores are usually non-infective and the bacteria are unlikely to spread. Dried up sores are also non-contagious.

Transmission of the infection occurs by:

  • Skin-to-skin contact.
  • Skin-surface contact.
  • Sharing the same towel.

Keep children with impetigo away from their nursery or playgroup till at least a couple of days of treatment are over. Encourage patients to wash their hands frequently, and use their own towels. Caregivers should also wash their hands whenever they touch their skin.


  • Fever and lymphadenopathy sometimes occur, more often with the bullous type.
  • Scarlet fever – occurrence of a pink rash over the body.
  • Cellulitis – infection of the deeper layers of the skin.
  • Scars, especially if the sores are scratched.
  • In rare cases, septicemia, if the infection spreads to the blood, requiring emergency intensive medical care.
  • Post-streptococcal acute glomerulonephritis – damage to the filtering units of the kidneys by streptococcal toxins.


Further Reading

    Last Updated: Nov 12, 2015

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