There are two types of bacteria called staphylococcus aureus and streptococcus pyogenes which cause impetigo. These bacteria harmlessly appear on the skin of a person and when there is a wound or a cut they cause infection. In adults the main cause of impetigo is the injury to the skin which is caused by other skin conditions like dermatitis. In children this infection is mainly caused due to insect bite, scrape or cut. There is also a possibility when children get infected with impetigo even where there is no skin damage.

This infection can pass from one person to other by touching the things which have been in contact with the infected person like towel, clothes, bed linen, toys and others.  Staphylococcus bacteria also produce a toxin which causes further spreading of this infection to nearby skin areas. The protein which keeps the skin cells bounded together is attacked by this toxin which gets damaged and leads to the spreading of the bacteria. The impetigo infection can start in two ways including primary impetigo and secondary impetigo. During primary impetigo the bacteria enters the skin through insect bite, cuts or other lesion whereas in secondary impetigo the bacteria enters the skin due to other skin infection or any other condition which disrupts the skin barrier like scabies or eczema.