Name: how acne forms and changes
Uploaded: 2026-03-12T13:35:45.000Z
Duration: 1 min 27 s
Channel: JoVE

Acne vulgaris is a skin condition characterized by inflammation of hair follicles. Overgrowth of Cutibacterium acnes, along with other factors, contributes to this inflammation.C. acnes is a Gram-positive, rod-shaped bacterium that thrives in the lipid-rich environment of sebaceous glands.During adolescence, increased androgen activity stimulates excessive sebum production.In some individuals, hyperproliferation of keratinocytes, along with trapped sebum in the hair follicle, forms a plug called a microcomedone.Inside this blocked follicle, C. acnes multiplies and secretes enzymes such as lipases, proteases, and hyaluronidases.These enzymes break down sebum and extracellular matrix components. This process irritates the surrounding tissue and triggers the release of immune signaling molecules, causing inflammation.This inflammation may lead to the formation of red papules or pus-filled pustules near the skin surface.If the follicular wall ruptures under pressure, the contents spread into the dermis. This spread may cause deeper inflammation and the formation of nodules or cysts.

acne infection

Acne Infection

Acne is a multifactorial skin condition primarily affecting adolescents and young adults, with a global prevalence estimated to exceed 75% in this demographic. The condition is characterized by the formation of comedones (blackheads and whiteheads), papules, pustules, nodules, and, in severe cases, cysts, particularly in areas rich in sebaceous glands such as the face, neck, chest, and back. The pathogenesis involves increased sebum production, follicular hyperkeratinization, colonization by Cutibacterium acnes (previously known as Propionibacterium acnes), and subsequent inflammation.Pathogen and Inflammatory MechanismA central microbial contributor to this process is C. acnes, whose biological activity contributes to initiating and sustaining the inflammatory response. C. acnes is a Gram-positive, non-spore-forming, anaerobic rod that resides deep within sebaceous follicles. It contributes to acne pathogenesis by producing factors that promote leukocyte recruitment to the follicle. Once there, leukocytes phagocytize the bacteria and release inflammatory mediators, which contribute to follicular rupture and surrounding tissue inflammation. This response is further mediated by innate immune mechanisms, including activation of Toll-like receptors (TLRs) and the release of pro-inflammatory cytokines such as IL-1&#946;, TNF-&#945;, and IL-8. The resultant immune response and accumulation of dead leukocytes contribute to the formation of pustules and the characteristic pus seen in acne lesions.Clinical Progression and TypesAcne lesions begin with comedones, which result from blocked sebaceous follicles. Blackheads (open comedones) and whiteheads (closed comedones) form due to oxidation or retention of sebum and keratin. Inflammatory lesions can progress to papules and pustules, and in more severe forms like cystic acne, deep nodules and ruptured cysts may result in permanent scarring.Treatment and PreventionMild acne often resolves without intervention, but persistent or severe cases may require treatment. Topical therapies such as benzoyl peroxide, which has keratolytic and antibacterial properties, and retinoids that normalize follicular keratinization are common. Antibiotics like erythromycin or doxycycline are used to target C. acnes, though resistance is a concern. In severe cases, systemic agents like isotretinoin (Accutane) are effective but carry significant teratogenic risks. Emerging non-chemical therapies, such as narrow-band ultraviolet light treatment, have shown promising results in reducing lesion counts, though their long-term efficacy and safety remain under investigation. Despite popular misconceptions, diet and hygiene have minimal impact on acne pathogenesis; the condition originates from within the follicle and is not significantly influenced by surface skin cleansing.

Acne is a multifactorial skin condition primarily affecting adolescents and young adults, with a global prevalence estimated to exceed 75% in this ...

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how acne forms and changes

Acne forms when pores in sebaceous skin become blocked and inflamed. It is a common skin condition in adolescents and young adults, and it often appears on the face, neck, chest, and back. The main lesions include comedones, papules, pustules, nodules, and, in severe cases, cysts.

The process starts with extra sebum production and follicular hyperkeratinization, which means the lining of the hair follicle sheds and thickens too much. These changes trap oil and keratin inside the follicle. Cutibacterium acnes, formerly called Propionibacterium acnes, then grows deep in the sebaceous follicle and helps trigger inflammation.

C. acnes is a Gram-positive, non-spore-forming, anaerobic rod. It promotes leukocyte recruitment to the follicle, and these immune cells phagocytize the bacteria. They then release inflammatory mediators, which can lead to follicular rupture and inflammation in nearby tissue.

Innate immune signals also play a role. Toll-like receptors, or TLRs, become activated, and pro-inflammatory cytokines such as IL-1β, TNF-α, and IL-8 are released. Dead leukocytes and the resulting immune response contribute to pus and the pustules seen in acne lesions.

Acne usually begins as comedones, which are blocked sebaceous follicles. Open comedones are blackheads, and closed comedones are whiteheads. Blackheads form when trapped material oxidizes, while whiteheads form when sebum and keratin remain sealed inside the pore.

Inflammatory acne can progress from papules to pustules. In more severe cases, deep nodules and ruptured cysts can develop, especially in cystic acne. These lesions may leave permanent scarring.

Mild acne may clear without treatment, but persistent or severe acne often needs care. Common topical treatments include benzoyl peroxide, which has keratolytic and antibacterial effects, and retinoids, which help normalize follicular keratinization. Antibiotics such as erythromycin or doxycycline can target C. acnes, although resistance is a concern.

Severe acne may be treated with isotretinoin, also known as Accutane, which is effective but carries major teratogenic risks. Narrow-band ultraviolet light therapy is another emerging option that has shown promise in reducing lesion counts. Its long-term safety and effectiveness are still being studied.

Popular ideas about acne and diet or hygiene are often misleading. The condition mainly starts inside the follicle, so surface cleansing has little effect on its development. Hygiene and diet have minimal impact on acne pathogenesis.

How Acne Forms and Changes

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Staphylococcus aureus can live harmlessly on the skin and mucous membranes of healthy people. When the skin barrier is broken, it can switch from a commensal organism to an opportunistic pathogen. It then uses surface adhesins, or attachment proteins, such as clumping factor B and Staphylococcus aureus surface protein G (SasG) to bind damaged epidermal proteins like loricrin and cytokeratin. After attachment, S. aureus uses immune evasion tools to stay on the skin. Protein A binds the Fc...

Acne forms when pores in sebaceous skin become blocked and inflamed. It is a common skin condition in adolescents and young adults, and it often appears on the face, neck, chest, and back. The main lesions include comedones, papules, pustules, nodules, and, in severe cases, cysts. The process starts with extra sebum production and follicular hyperkeratinization, which means the lining of the hair follicle sheds and thickens too much. These changes trap oil and keratin inside the follicle.

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key terms and concepts

Learn how acne develops from blocked follicles, C. acnes activity, and inflammation, plus how blackheads, pustules, and severe cystic acne form.

How Acne Forms and Changes | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

How Acne Forms and Changes

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