Impetigo is a highly contagious bacterial skin infection, usually caused by Group A streptococcus or Staphylococcus aureus bacteria. Impetigo is most common in children. However, it sometimes occurs in adults who have other itchy skin conditions, such as eczema. Other conditions that increase your risk of developing impetigo include chickenpox, reactions to insect bites, burns of the skin and diabetes.
Impetigo often appears around the nose and mouth. However, it can develop wherever the skin is broken by cuts, scrapes, scratching, or cold sores, and where bacteria can enter.