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Salem Health: Infectious Diseases & Conditions, 2nd Edition

Impetigo

by Amy Scholten

Category: Diseases and conditions

Anatomy or system affected: Skin

Definition

Impetigo is a highly contagious bacterial skin infection.

Causes

Impetigo is caused by one or both of the following types of bacteria: group A Streptococcus and Staphylococcus. These bacteria are normally found on the skin and in the nose. When small cuts, scratches, or insect bites occur, these bacteria can get under the skin and cause infection. Impetigo is often spread from person to person.

Risk Factors

Factors that increase the chance for impetigo include touching a person with impetigo; touching the clothing, towels, sheets, or other items of a person with impetigo; poor hygiene, particularly unwashed hands and dirty fingernails; crowded settings where there is direct person-to-person contact, such as in schools and in the military; a warm, humid environment; and the summer season.

A culture plate containing a species of Streptococcus bacteria, which causes impetigo and other infectious diseases. Image courtesy of the CDC via Public Health Image Library.

Infect2e_p0579_1.jpg

At higher risk are preschool and school-age children; persons in poor health or who have a weakened immune system; and persons who tend to have skin problems, such as eczema, poison ivy, or skin allergy. Other risk factors are getting cuts, scratches, or insect bites, or experiencing other injury or trauma to the skin; having chickenpox; and having a lice infection, such as scabies, head lice, or pubic lice, which cause scratching.

Symptoms

Symptoms of impetigo, which appear four to ten days after exposure, include red spots, sores, or blisters on the skin of the face, arms, legs or other parts of the body that ooze and become covered with a flat, dry, honey-colored crust; itch; and may increase and spread, especially if scratched.

Other symptoms, in more serious cases, include swollen lymph nodes. Normally, impetigo is a fairly mild condition. However, if left untreated, further problems could develop, including pain, swelling, spread of infection, discharge of pus, and fever. In rare cases, people whose impetigo is caused by groupA Streptococcus may develop glomerulonephritis, scarlet fever, or life-threatening invasive streptococcal disease.

Screening and Diagnosis

A doctor will examine the patient’s skin lesions and ask about symptoms and medical history. Initial diagnosis is based on the appearance of the skin lesions. If the patient has impetigo, a culture of his or her skin lesion may be done. The culture will show what specific bacteria are involved.

Treatment and Therapy

The goals of treatment are to relieve the symptoms and cure the infection. Treatment may include the use of antibiotics. For a mild infection, the patient may get a prescription topical antibiotic, such as mupirocin or retapamulin; an over-the-counter topical antibiotic(significantly less effective), such as neomycin, bacitracin, or polymyxin; or an oral antibiotic, such ascephalosporin or a penicillin. In some cases, staphylococcal infections (such as methicillin-resistant staph infection) may be resistant to these antibiotics. In these cases, other options may be needed.

One should not touch or scratch the lesions. Also, one should wash the skin several times a day with water and an antibiotic soap. The crusts of the lesions are removable by soaking the infected area in warm water for about fifteen minutes. Lesions should be covered loosely with gauze, a bandage, or clothing.

Prevention and Outcomes

Prevention of impetigo involves good personal hygiene, including bathing daily with soap and water and washing one’s face, hands, and hair regularly; washing hands after caring for someone with impetigo; not sharing towels, clothes, or sheets with a person who has impetigo; keeping fingernails short and clean; changing and washing clothing frequently; not allowing one’s children to play or have close contact with someone who may have impetigo; promptlywashing wounds, such as cuts, scratches, or insect bites, with soap and water and applying a small amount ofantibiotic ointment and a bandage to the affected area.

To help avoid spreading the infection, one should wash hands thoroughly, especially after touching an infected area of the body; should avoid contact with newborns; should stay home until twenty-four hours after the start of treatment; and should not handle food at home until a minimum of twenty-four hours after the start of treatment.

Further Reading

1 

Bhumbra, Nasreen A., and Sophia G. McCullough. “Skin and Subcutaneous Infections.” In Update on Infectious Diseases, edited by Richard I. Haddy and Karen W. Krigger. Philadelphia: W. B. Saunders, 2003.

2 

Crossley, Kent B., Kimberly K. Jefferson, and Gordon L. Archer, eds. Staphylococci in Human Disease. Hoboken, N.J.: John Wiley & Sons, 2009.

3 

Koning, S., et al. “Efficacy and Safety of Retapamulin Ointment as Treatment of Impetigo: Randomized-Double-Blind Multicentre Placebo-Controlled Trial.” British Journal of Dermatology 158, no. 5 (2008): 1077-1082.

4 

Swartz, Morton N., and Mark S. Pasternack. “Cellulitis and Subcutaneous Tissue Infection.” In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John E. Bennett, and Raphael Dolin. 7th ed. New York: Churchill Livingstone/Elsevier, 2010.

5 

Taylor, Julie Scott. “Interventions for Impetigo.” American Family Physician 70, no. 9 (November 1, 2004).

Web Sites of Interest

American Academy of Dermatology

http://www.aad.org

American Osteopathic Association

http://www.osteopathic.org

Dermatologists.ca

http://www.dermatologists.ca

KidsHealth

http://www.kidshealth.org

See also: Acanthamoeba infections; Bacterial infections; Cellulitis; Chickenpox; Children and infectious disease; Contagious diseases; Erythema nodosum; Group A streptococcal infection; Insect-borne illness and disease; Methicillin-resistant staph infection; Pityriasis rosea; Roseola; Rubella; Scarlet fever; Skin infections; Staphylococcal infections; Staphylococcus; Streptococcal infections; Streptococcus.

Citation Types

Type
Format
MLA 9th
Scholten, Amy. "Impetigo." Salem Health: Infectious Diseases & Conditions, 2nd Edition, edited by H. Bradford Hawley, Salem Press, 2020. Salem Online, online.salempress.com/articleDetails.do?articleName=Infect2e_0302.
APA 7th
Scholten, A. (2020). Impetigo. In H. B. Hawley (Ed.), Salem Health: Infectious Diseases & Conditions, 2nd Edition. Salem Press. online.salempress.com.
CMOS 17th
Scholten, Amy. "Impetigo." Edited by H. Bradford Hawley. Salem Health: Infectious Diseases & Conditions, 2nd Edition. Hackensack: Salem Press, 2020. Accessed September 16, 2025. online.salempress.com.