Impetigo Conferta Capilitii on top of infant's head, 1841. Impetigo is a bacterial infection that involves the superficial skin. The most common presentation is yellowish crust on the face, arms, or legs. Less commonly there may be large blisters which affect the groin or armpits. The lesions may be painful or itchy. It is typically due to either Staphylococcus aureus or Streptococcus pyogenes. Risk factors include attending daycare, crowding, poor nutrition, diabetes, contact sports, and breaks in the skin such as from mosquito bites, eczema, or scabies. Robert Willis.