What Is Impetigo Caused By?

Reviewed on 9/22/2020

What Is Impetigo?

Impetigo is a contagious bacterial skin infection that commonly affects children age two to five years, though older children and adults may also be affected. It occurs when bacteria get into cuts, scrapes, or other small openings in the skin.

Impetigo is most common in places where the weather is warm and humid and spreads easily among people who are in close contact.

What Are Symptoms of Impetigo?

Symptoms of impetigo include: 

  • Red bumps on the skin
    • Usually on the face, arms, or legs
    • Bumps later form blisters that burst and scab over
    • The scabs form a yellow, gold, or brown crust
    • In some cases, the blisters leave painful sores with red rims

What Causes Impetigo?

Impetigo is usually caused by the Staphylococcus aureus bacterium, a type of "staph" infection. 

Less commonly, impetigo is caused by streptococcus group A ("strep") or by both bacteria.

How Is Impetigo Diagnosed?

Impetigo can often be diagnosed by a physical examination of the skin. 

Tests used to confirm impetigo and to identify whether S. aureus and/or a beta-hemolytic Streptococcus is the cause may include: 

  • Gram stain 
  • Culture of pus or exudate

What Is the Treatment for Impetigo?

Impetigo is usually treated with topical or oral antibiotics.

If the impetigo is mild and there are just a few affected spots that do not appear to penetrate deeply into the skin, topical antibiotic cream or ointment may be recommended. If the infection is deep or widespread, oral antibiotics may be prescribed. 

Topical antibiotics used to treat impetigo include: 

Systemic antibiotics used to treat impetigo include: 

Treatment for patients with confirmed methicillin-resistant S. aureus (MRSA) infections includes: 

What Are Complications of Impetigo?

Complications of impetigo are not common but may include: 

  • Cellulitis (infection of deeper layers of skin)
  • Guttate psoriasis 
  • Scarlet fever 
  • Septicemia (bacterial infection of the blood which can be life-threatening)
  • Post-streptococcal glomerulonephritis (infection of the small blood vessels in the kidneys) (rare) 

How Do You Prevent Impetigo?

Impetigo is spread from person to person through direct skin-to-skin contact. To prevent impetigo: 

  • Wash your hands frequently with soap and warm water for at least 20 seconds, or use an alcohol-based hand sanitizer 
  • Do not share personal items, such as towels, clothes, or hair accessories
  • Wash towels and bedding in hot water and dry them on high heat
  • If you have impetigo, cover the parts of your skin that are infected
  • Use disposable tissues to blow your nose, discard tissues immediately in the trash, and wash your hands after handling tissues 
  • Sneeze into the crook of your arm or into your shoulder, and not into your hands 


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Reviewed on 9/22/2020