The microcomedo may takes up the size and turns into Blackhead OR Whitehead.
A natural occurring flora Propionibacterium acnes lives in side the sebaceous glands on fatty acid harmless but blockade of the follicle lead to over growth of the bacteria spilling toxins and breakdown wall pore spilling bacteria such as Staphylococcus aureus.
This causes swelling, inflammation which becomes pus containing cells called pustules, nodules.
Hormones
Increased activity of hormones plays a major role in acne. Hormonal activity is at its peak during,Menstrual cyclePuberty,