Why Acne Can Persist Even After Bacteria Are Reduced
When someone struggles with acne, the natural assumption is that bacteria causes the problem. This makes sense on the surface – acne does involve bacteria, specifically a microorganism called Cutibacterium acnes. However, the reality is far more complicated. Even when bacteria levels drop significantly through treatment, acne can continue to appear. Understanding why requires looking beyond the bacteria itself.
The key insight is that acne is not simply a bacterial infection. It is a chronic inflammatory disorder of the skin that involves multiple interconnected factors working together. Bacteria alone does not determine whether someone develops acne. Many adults have abundant amounts of Cutibacterium acnes living on their skin without ever experiencing breakouts. The difference lies in strain-level variations, individual host factors, and the specific microenvironment of the skin. This means that two people with identical bacterial levels can have completely different acne outcomes.
Hormones play a major role in acne persistence. When hormone levels shift, particularly when androgens increase relative to estrogen, the sebaceous glands produce excess oil. This excess sebum can clog pores and create an environment where bacteria thrive. Even if antibacterial treatments reduce bacterial populations, the underlying hormonal imbalance remains. The glands continue producing too much oil, pores stay clogged, and new bacteria can colonize these blocked follicles. For women, hormonal fluctuations during menstruation, pregnancy, menopause, or conditions like polycystic ovary syndrome can trigger persistent acne that antibacterial treatments alone cannot resolve.
The skin barrier itself matters tremendously. When people aggressively treat acne with strong antibacterial products or wash their faces too frequently, they can damage the protective barrier of the skin. A compromised barrier allows bacteria and irritants to penetrate more easily, which paradoxically increases inflammation and can worsen breakouts. Additionally, when the skin barrier is damaged, the skin may produce even more oil to compensate, creating a cycle that perpetuates acne despite reduced bacterial counts.
Inflammation is another critical factor that persists independently of bacterial levels. Even when bacteria are reduced, the immune system’s inflammatory response can continue. The body’s reaction to bacterial byproducts, dead skin cells, and other irritants keeps the skin inflamed and prone to breakouts. This inflammatory state can last long after bacterial populations have been controlled.
The process of how bacteria damages skin also matters. Cutibacterium acnes produces enzymes like lipases, hyaluronidases, and proteases that break down skin components and trigger inflammation. These bacterial byproducts can cause damage that takes time to heal, even after the bacteria themselves have been eliminated. Additionally, bacteria can form biofilms – protective structures that shield them from immune defenses and antibiotics. Even if most bacteria are killed, some protected within biofilms can survive and re-establish populations.
Skin cell turnover and pore clogging continue regardless of bacterial reduction. Acne involves hyperkeratinization, which means skin cells are not shedding properly and accumulate inside pores. Dead skin cells mixed with sebum create blockages that trap bacteria. Simply reducing bacteria does not address this underlying cell turnover problem. Without treating the clogged pores themselves, new bacteria will continue to colonize these blocked follicles.
Diet and lifestyle factors can sustain acne even when bacteria are controlled. Foods high in dairy or sugar can spike insulin and androgen activity, worsening sebum production. Stress increases cortisol and other hormones that boost oil production and inflammation. Poor sleep and high stress levels contribute to acne flare-ups through multiple pathways. These factors operate independently of bacterial levels.
The complexity of acne means that effective treatment requires addressing multiple causes simultaneously. Antibacterial treatments alone target only one piece of the puzzle. Successful acne management often requires combining approaches – perhaps using retinoids to regulate skin cell turnover, addressing hormonal imbalances with appropriate medications, reducing inflammation, maintaining a healthy skin barrier, and making dietary or lifestyle adjustments. A board-certified dermatologist can help identify which factors are driving an individual’s acne and create a comprehensive treatment plan that goes beyond simply reducing bacteria.
Sources
https://pmc.ncbi.nlm.nih.gov/articles/PMC12735603/
https://www.tuftsmedicine.org/about-us/news/acne-over-30
https://www.medicaldaily.com/hormonal-acne-adults-acne-causes-skin-hormones-explained-474128
