Under normal conditions, the human body is inhabited by many microorganisms, which constitute a large micro-ecological world and maintain a stable biological environment for the organism. This is one of the important reasons why the normal organism is “invulnerable to all diseases”. There are three groups of microorganisms living in the sebaceous glands of hair follicles: Propionibacterium acnes, Staphylococcus albicans, and Onychobacterium furfur. These three microorganisms have a variety of biological functions, all of which can break down fat and produce free fatty acids, but Propionibacterium acnes is the most important. Propionibacterium acnes is a gram-negative anaerobic bacterium in the sebaceous glands of hair follicles,
It grows fastest in near-neutral environments and is inhibited in environments with pH ≤5 or ≥8. It relies on sebum, especially triglycerides, in the hair follicle for nutrition and prefers to colonize sebum-rich environments.
Propionibacterium acnes is rare in children and proliferates after puberty due to the increase in the amount of sebum. It can produce lipase, protease, hyaluronidase and inflammatory factors. Among them, lipase can metabolize triglycerides in the follicular funnel into free fatty acids, stimulating inflammation in the follicle, resulting in damage to the follicle wall and rupture, which in turn leads to the escape of exfoliated keratinized epithelial cells, sebum, free fatty acids in sebum and Propionibacterium acnes into the dermis, producing deep inflammation mainly around the follicle. In addition, Propionibacterium acnes can also act as a superantigen causing an immune response, which can lead to secondary inflammation.
In addition, the severity of acne may also be related to factors such as the proliferation of Propionibacterium acnes.
Therefore, it is indisputable that alterations in local microecology are closely related to the production, development and outcome of acne.