Acne The presence of pimples in oily areas indicates acne. Acne is considered a skin type because the tendency to develop acne is hereditary. Acne is a disorder in which the hair follicles become clogged, resulting in infection of the follicle with redness and inflammation. Acne bacteria are anaerobic, which means they cannot survive in the presence of oxygen. When follicles are blocked with solidified sebum and dead-cell buildup, oxygen cannot readily get to the bottom of the follicle where acne bacteria live. Acne bacteria survive from breaking down sebum into fatty acids, which is their only food source. A blocked follicle is an ideal environment for acne bacteria. When acne bacteria flourish from the lack of oxygen and access to a food source such as a blocked follicle filled with sebum, they multiply quickly, eventually causing a break in the follicle wall. This rupture allows blood to come into the follicle causing redness. Acne papules are red pimples that do not have a pus head. Pimples with a pus head are called pustules. Pus is a fluid inside a pustule, largely made up of dead white blood cells that tried to fight the infection.