From the Guidelines
Acne vulgaris is a chronic inflammatory skin condition rather than a true infection, though bacteria play a role in its pathogenesis. The disease develops through four key mechanisms: excessive sebum production, abnormal follicular keratinization, colonization by Cutibacterium acnes, and inflammation 1. Hormonal influences, particularly androgens, stimulate sebaceous glands to produce more sebum. Simultaneously, abnormal shedding of skin cells leads to follicular plugging. While C. acnes bacteria naturally inhabit the skin, they proliferate in this oil-rich, oxygen-poor environment, breaking down sebum into free fatty acids and releasing inflammatory mediators.
Key Factors in Acne Pathogenesis
- Excessive sebum production
- Abnormal follicular keratinization
- Colonization by Cutibacterium acnes
- Inflammation Despite bacterial involvement, acne is not considered an infection because C. acnes is a normal skin commensal, not an invading pathogen. The bacteria don't directly cause tissue invasion or destruction characteristic of true infections. Furthermore, acne's chronic, relapsing nature, genetic predisposition, and hormonal influences align more with disease states.
Treatment Approaches
The effectiveness of non-antimicrobial treatments (like retinoids, hormonal therapies) and the fact that antibiotics work primarily through anti-inflammatory rather than antimicrobial effects support classifying acne as an inflammatory disease with bacterial contribution rather than a primary infection 1. Treatment approaches targeting multiple pathogenic factors rather than just bacteria further reinforce this classification. For example, guidelines recommend multimodal therapy combining multiple mechanisms of action, including benzoyl peroxide, topical retinoids, and topical antibiotics 1.
Rationale for Classification as a Chronic Disease
The chronic nature of acne, its impact on quality of life, and the involvement of multiple pathogenic factors support its classification as a chronic disease rather than an infection. The health-related quality of life impact of acne is comparable to that of chronic conditions such as asthma, psoriasis, and arthritis 1. Acne is associated with increased risks of stigmatization, bullying, depression, anxiety, poor self-esteem, and suicidal ideation, further emphasizing its significance as a chronic disease. The multifactorial pathogenesis of acne and its chronic, relapsing nature justify its classification as a chronic inflammatory skin condition rather than a true infection.
From the Research
Pathogenesis of Acne Vulgaris
- Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit, involving the hair follicle, hair shaft, and sebaceous gland 2.
- The development of acne involves several key mechanisms, including disturbed sebaceous gland activity, alterations in sebum fatty acid composition, dysregulation of the hormone microenvironment, interaction with neuropeptides, follicular hyperkeratinization, induction of inflammation, and dysfunction of the innate and adaptive immunity 2.
- The gram-positive and anaerobic Propionibacterium acnes (P. acnes) bacterium has been implicated in acne inflammation and pathogenesis 3.
Infection or Disease State
- Acne vulgaris is not considered an infection in the classical sense, but rather a chronic disease state characterized by inflammation and immune system dysfunction 2, 4.
- While P. acnes is present in acne lesions, the disease is not solely caused by the bacterium, but rather by a complex interplay of factors, including hormonal, genetic, and environmental influences 4, 3.
Rationale for Acne as a Chronic Disease
- Acne vulgaris is a chronic condition that can persist for years, with periods of remission and exacerbation 5, 6.
- The disease is characterized by a complex pathophysiology, involving multiple factors and pathways, which cannot be explained by a simple infection model 2, 4.
- Treatment of acne vulgaris requires a long-term approach, with a focus on managing symptoms, preventing scarring, and improving quality of life, rather than simply eradicating a causative agent 5, 6.
Arguments Against Acne as an Infection
- The presence of P. acnes in acne lesions does not necessarily imply a causal relationship, as the bacterium is also present on healthy skin 3.
- Antibiotic therapy, while effective in reducing inflammation, does not eradicate P. acnes, and resistance to antibiotics is a growing concern 4, 3.
- The disease is characterized by a complex interplay of hormonal, genetic, and environmental factors, which cannot be explained by a simple infection model 2, 4.