Acne vulgaris is a common skin disorder which usually occurs in adolescence. It typically affects the face, neck and upper trunk and is characterised by the obstruction of the pilosebaceous follicle with keratin plugs which results in comedones, inflammation and pustules.


  • Incidence: 2000.00 cases per 100,000 person-years
  • Peak incidence: 20-30 years
  • Sex ratio: 1:1
Condition Relative
Acne vulgaris1
Periorificial dermatitis0.10
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


  • affects around 80-90% of teenagers, 60% of whom seek medical advice
  • acne may also persist beyond adolescence, with 10-15% of females and 5% of males over 25 years old being affected

Pathophysiology is multifactorial
  • follicular epidermal hyperproliferation resulting in the formation of a keratin plug. This in turn causes obstruction of the pilosebaceous follicle. Activity of sebaceous glands may be controlled by androgen, although levels are often normal in patients with acne
  • colonisation by the anaerobic bacterium Propionibacterium acnes
  • inflammation

Clinical features

Acne is a disease of the pilosebaceous unit. Several different types of acne lesions are usually seen in each patient

Comedones are due to a dilated sebaceous follicle
  • if the top is closed a whitehead is seen
  • if the top opens a blackhead forms

Inflammatory lesions form when the follicle bursts releasing irritants
  • papules
  • pustules

An excessive inflammatory response may result in:
  • nodules
  • cysts

This sequence of events can ultimately cause scarring
  • ice-pick scars
  • hypertrophic scars

In contrast, drug-induced acne is often monomorphic (e.g. pustules are characteristically seen in steroid use)

Acne fulminans is very severe acne associated with systemic upset (e.g. fever). Hospital admission is often required and the condition usually responds to oral steroids


Acne may be classified into mild, moderate or severe:
  • mild: open and closed comedones with or without sparse inflammatory lesions
  • moderate acne: widespread non-inflammatory lesions and numerous papules and pustules
  • severe acne: extensive inflammatory lesions, which may include nodules, pitting, and scarring

A simple step-up management scheme often used in the treatment of acne is as follows:
  • single topical therapy (topical retinoids, benzoyl peroxide)
  • topical combination therapy (topical antibiotic, benzoyl peroxide, topical retinoid)
  • oral antibiotics:
    • tetracyclines: lymecycline, oxytetracycline, doxycycline
    • tetracyclines should be avoided in pregnant or breastfeeding women and in children younger than 12 years of age
    • erythromycin may be used in pregnancy
    • minocycline is now considered less appropriate due to the possibility of irreversible pigmentation
    • a single oral antibiotic for acne vulgaris should be used for a maximum of three months
    • a topical retinoid (if not contraindicated) or benzoyl peroxide should always be co-prescribed with oral antibiotics to reduce the risk of antibiotic resistance developing
    • Gram-negative folliculitis may occur as a complication of long-term antibiotic use - high-dose oral trimethoprim is effective if this occurs
  • combined oral contraceptives (COCP) are an alternative to oral antibiotics in women
    • as with antibiotics, they should be used in combination with topical agents
    • Dianette (co-cyrindiol) is sometimes used as it has anti-androgen properties. However, it has an increased risk of venous thromboembolism compared to other COCPs, therefore it should generally be used second-line, only be given for 3 months and women should be appropriately counselled about the risks
  • oral isotretinoin: only under specialist supervision

There is no role for dietary modification in patients with acne.