Impetigo is a skin infection caused by bacteria, resulting in a red rash, blisters, and a characteristic honey-colored crust on the skin. Impetigo most commonly occurs in infants and children age 2 to 6.
There are three forms of impetigo:
Nonbullous impetigo is the most common and mildest form of impetigo, causing small blisters on the skin.
Bullous impetigo produces much larger blisters.
Ecthyma is the most serious form of impetigo, affecting deeper levels of skin (dermis layer).
Impetigo is usually caused by Staphylococcus aureus or Streptococcus pyogenes bacteria. This highly contagious infection is spread from one person to the next by direct contact with the lesions or secretions of an infected person. The condition occurs on areas of skin where a person has a pre-existing scratch, cut or break in the skin through which the bacteria can enter.
Risk factors include:
Young age (infants and young children)
Warm temperatures or summer season
Contact sports, such as wrestling or football
Breaks in the skin.
Typically an individual with impetigo experiences the onset of symptoms within 1 to 3 days after acquiring the infection. The initial symptom of impetigo is a red rash, usually located on the face, arms or legs.
Nonbullous impetigo typically causes a rash on the face around the mouth and nose. The rash begins as small red pimples (papules). The infection progresses to form small fluid-filled blisters or lesions filled with pus (pustules). After several days, the blisters and pustules rupture and weep, forming the classic honey-colored crusts.
Bullous impetigo is associated with larger fluid-filled blisters, pustules, and honey-colored crusts that often affect the diaper area and trunk.
Ecthyma is a severe form of impetigo associated with deep punched-out ulcers, which extend into the dermis, and a honey-colored crust.
Severe forms of impetigo may lead to the following major complications:
Cellulitis, a widespread bacterial skin infection, affects surrounding areas and tissues beneath the dermis. In extreme cases of cellulitis, bacteria enter the bloodstream, resulting in a life-threatening illness.
Kidney damage and impaired kidney function may occur with streptococcal forms of impetigo.
Permanent scarring may result from ecthyma because of deep skin involvement.
Diagnosis and Treatment
Impetigo is usually diagnosed by visually observing the characteristic skin rash with honey-colored crust, so, in most cases, there is no need for additional testing. Sometimes, the fluid from weeping areas is tested in a laboratory to confirm the diagnosis and identify the bacteria involved.
Left untreated, the infection normally resolves itself in approximately 3 weeks. However, treatment with medication clears the infection much faster.
Treatment includes the following:
Topical antibiotic ointment applied externally to the skin treats mild cases of impetigo with few blisters. A prescription strength medication (Mupirocin ointment) is more effective than over-the-counter topical antibacterial products.
Oral antibiotics are prescribed for more severe skin infections with large, widespread lesions. Commonly prescribed oral antibiotics include cephalexin, dicloxacillin, and erythromycin.
Antibacterial soap helps clean the affected skin.
Impetigo is highly contagious and easily transmitted to others through contact with infected skin, shared objects, clothing and linens. The best way to prevent impetigo is to avoid contact with infected people and contaminated objects. Hand washing is considered vital in reducing the spread of infections. Additionally, the infection is only acquired when there is a break or cut on the skin, so children should be taught to avoid scratching, and their fingernails should be kept properly trimmed. After 48 hours of antibiotic treatment, a person with impetigo is no longer contagious.
Lawley LP, McCall CO, Lawley TJ. Chapter 52. Eczema, Psoriasis, Cutaneous Infections, Acne, and Other Common Skin Disorders. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison’s Principles of Internal Medicine, 18e. New York, NY: McGraw-Hill; 2012.
Impetigo. Mayo Clinic website. http://www.mayoclinic.org/diseases-conditions/impetigo/basics/definition/con-20024185. Accessed December 15, 2014.
Impetigo. National Institute of Allergy and Infectious Diseases, National Institute of Health website. http://www.niaid.nih.gov/topics/impetigo/Pages/Default.aspx. Accessed December 15, 2014.
Bacterial Skin Infections. American Academy of Dermatology website. https://www.aad.org/education/basic-dermatology-curriculum/suggested-order-of-modules/four-week-rotation/week-2/bacterial-skin-infections. Accessed December 15, 2014.
Tina is a Life Science Writer for a number of online publications, including Innerbody.com. Her expertise is in conveying complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. In her spare time, she enjoys drawing science-related cartoons.