Impetigo is a highly contagious bacterial infection of the surface layers of the skin, which causes sores and blisters.  It can be quite itchy but it is important not to scratch. It is treated with topical antibiotics or in more severe cases oral antibiotics might be required. If it is recurrent your Doctor may want to take a nasal swab.  It is highly contagious so children should be kept away from school until they are on antibiotics for at least 24 hours and should not share towels etc.