• Clinical science

Acne vulgaris


Acne vulgaris is a common skin disease that affects most individuals at some point in their lives. It is classified into different forms which vary in severity, lesion type, and localization, with the face commonly involved. The hallmark of acne are comedones, which can develop further into inflammatory papules, pustules, or even abscesses and nodules. Symptoms typically begin in early puberty and cease spontaneously during the third decade of life. The are multiple etiological factors: genetic predisposition, seborrhea, and hyperkeratosis are known to promote the development of acne. Topical and systemic treatment options are available to counteract inflammation and hyperkeratosis, as well as to help purify the skin.


  • Prevalence: 85% of the population is affected (!)
  • Age of onset: typically by 11–12 years, with symptoms usually disappearing around 20–30 years of age
  • Sex: more common in males during adolescence, but more common in women during adulthood


Epidemiological data refers to the US, unless otherwise specified.


  • Genetic predisposition
  • Hormonal factors
  • Follicular hyperkeratosis
  • Bacterial colonization; with Cutibacterium acnes (formerly known as Propionibacterium acnes)
  • External factors, such as climate, drugs, or food


Clinical features

  • Localization: common in areas with sebaceous glands (predilection sites: face, shoulders, upper chest, and back)
  • Primary lesions
    • Non-inflammatory: comedonal acne
      • Closed comedones (“whiteheads”): closed small round lesions that contain whitish material (sebum and shed keratin)
      • Open comedones (“blackheads”): dark, open portion of sebaceous material
    • Inflammatory: affected areas are red and can be painful
  • Secondary lesions: postinflammatory erythema, hyperpigmentation, and scarring


Subtypes and variants

  • Hidradenitis suppurativa (also acne inversa): inflammation of the hair follicles, most likely triggered by a blockage
    • Risk factors: obesity, smoking, family history
    • Clinical presentation
      • Localization: in folded skin areas (most commonly the axillae, groin, inner thigh, and perineal area)
      • Formation of abscesses, fistulas, and keloids
      • Formation of draining sinuses with scarring and foul odor
    • Treatment
      • Antibiotics, retinoids
      • Reduce body weight, stop smoking
      • If insufficient: incision, surgical removal
  • Neonatal acne
    • Age of onset: first few weeks of life
    • Clinical presentation: papulopustular rash
    • Treatment: self-limiting disease ; no specific treatment
  • Infantile acne
    • Age of onset: ≥ 3 months
    • Clinical presentation: papulopustular rash, closed comedones, and sometimes formation of nodules. More common in boys.
    • Treatment: In contrast to neonatal acne, treatment is indicated to avoid scarring



Acne treatment

Mild (e.g., comedonal) Moderate (e.g., papular/pustular) Severe (e.g., conglobata)
  • Combination therapy:
    • Topical benzoyl peroxide AND topical retinoids/ antibiotics
    • Oral antibiotic (tetracycline-class) may be added
    • Combined oral contraceptives may be added (in females)
  • Oral isotretinoin
  • Or oral antibiotics (tetracycline-class) AND topical combination therapy
  • Combined oral contraceptives may be added (in females)
  • Therapy is particularly important for patients with inflammatory acne to prevent complications such as scarring.


  • Main substance: isotretinoin (Vitamin A derivative) given systemically
    • Indication: in moderate to severe acne
    • Mechanism of action: Retinoids normalize keratinization by inhibiting and modulating keratinocytessebum production
    • Contraindications
      • Pregnancy, women of childbearing age without contraception: strong teratogenic effects
      • Liver disease
      • Simultaneous tetracycline treatment
    • Precautions (in all females of childbearing potential)
      • 1 month before initiating therapy:
        1. A serum / urine pregnancy test
        2. Two methods of contraception (oral contraceptive therapy + barrier contraception / IUD)
      • During therapy: monthly pregnancy test and continuous use of two methods of contraception
      • After completing therapy:
        1. Continue two methods of contraception for 1 month
        2. A pregnancy test at the end of 1 month
    • Side effects

Retinoid therapy should be discontinued at latest one month before planned conception!