There are two clinical types, impetigo contagiosa and bullous impetigo. Impetigo contagiosa is the most common form. Usually caused by Staphylococcus aureus, streptococci or both, depending on geographical variations, with the streptococcal form being more prevalent in warmer climates. The early lesion of impetigo contagiosa is a very thin-walled vesicle that develops on an erythematous base. The vesicles rupture rapidly, and as a result, they are seldom seen.