Impetigo (pronounced im-puh-TIE-go) is a contagious, superficial infection of the skin caused by staphylococcus (Staph) and streptococcus (Strep) bacteria. Impetigo is more common in children (especially 2- to 5-year-olds) than in adults. Impetigo is most likely to occur in warm and humid environments and is most commonly spread by close contact (such as family members).
If you pick at sores or scratch itchy bites, you may cause bacteria to enter your skin and cause impetigo.
- Bacteria get below the surface of the skin, usually by some sort of break in the skin. Typically, the break in the skin will be noticed (such as a skinnedknee or a cut, even an insect bite), but a very small, even microscopic, break is common.
- Once the bacteria get into the inner layers of the skin, they grow and multiply, creating a blister. Usually, this blister becomes filled with pus and bursts, leaving a crust.
Impetigo shows up as a rash that may occur anywhere on the body and commonly affects the face and other exposed areas of the body.
- The rash may be blisterlike, reddish, have a "honey" colored crust, or very commonly will have a combination of all 3.
- The margins of the rash are usually fairly sharp.
- The rash is sometimes mildly painful and is commonly itchy.
Two types of bacteria cause impetigo — Staphylococcus aureus (staph), which is most common, and Streptococcus pyogenes (strep). Both types of bacteria can live harmlessly on your skin until they enter through a cut or other wound and cause an infection.
In adults, impetigo is usually the result of injury to the skin — often by another dermatological condition such as dermatitis. Children are commonly infected through a cut, scrape or insect bite, but they can also develop impetigo without having any notable damage to the skin.
You're exposed to the bacteria that cause impetigo when you come into contact with the sores of someone who's infected or with items they've touched, such as clothing, bed linen, towels and even toys. Once you're infected, you can easily spread the infection to others.
Staph bacteria produce a toxin that causes impetigo to spread to nearby skin. The toxin attacks a protein that helps bind skin cells together. Once this protein is damaged, bacteria can spread quickly.
Impetigo is not serious and is easy to treat. Mild cases can be handled by gentle cleansing, removing crusts and applying the prescription-strength antibiotic ointmentmupirocin (Bactroban). Non prescription topical antibiotic ointments (such as Neosporin) generally are not effective. More severe or widespread cases, especially of bullous impetigo, may require oral antibiotic medication. In recent years, more Staph germs have developed resistance to standard antibiotics. Bacterial culture tests can help guide the use of proper oral therapy if needed.
Antibiotics which can be helpful include penicillin derivatives (such as Augmentin) and cephalosporins such ascephalexin (Keflex). If clinical suspicion supported by culture results show other bacteria, such as drug-resistant Staph (methicillin-resistant Staphylococcus aureus or MRSA), other antibiotics such as clindamycin or trimethoprim-sulfamethoxazole (Bactrim or Septra) may be necessary. Treatment is guided by laboratory results (culture and sensitivity tests).
What are possible complications of impetigo?
One potentially serious but rare complication of impetigo caused by Strep bacteria is glomerulonephritis, a condition producing kidney inflammation. Many specialists are not convinced that treating impetigo will prevent glomerulonephritis from occurring.
Will impetigo leave scars?
Because the crusts and blisters of impetigo are superficial, impetigo does not leave scars. Affected skin looks red for a while after the crusts go away, but this redness fades in a matter of days to weeks.