The term zits is used to describe acne. It can be used to refer to whiteheads, blackheads or other types of pimples or blemishes on the skin. Zits are caused in part by a build up of oils in the pores of the skin, where the hair grows out from the follicle. When oils build up here, bacteria are able to grow and flourish in the area, which further causes an infection on the skin. Zits are not contagious infections, but they can be serious health conditions if they do break open due to scratching. This can lead to a more serious infection.