7th June 2025

Acne

Acne vulgaris is a chronic inflammatory skin condition which predominantly affects the face, back and chest. It can present in any age group but peaks in adolescence, affecting 8 in 10 teenagers. Acne is characterised by blockage and inflammation of the pilosebaceous unit (the hair follicle, hair shaft and sebaceous gland) which manifests as comedones, papules, pustules, nodules, cysts and/or scarring. It can have a profound social and psychological impact on patients and hence there is a significant need for effective acne treatment.

Cause

Acne is a multifactorial disease with the following primary pathogenic factors:

• Increased sebum production stimulated by androgens, within sebaceous follicles 
• Follicular hyperkeratinisation leading to follicular plugs (comedones) 
• Proliferation of Cutibacterium acnes within sebum in hair follicles
• Release of inflammatory cells and mediators leading to development of papules, pustules, nodules and cysts.

Other factors that could contribute to acne pathogenesis include:

• Genetic factors (high prevalence among identical twins)
• High glycaemic index diets, dairy and meat products high in leucine 
• Hormonal factors (menstrual period related, hyperandrogenism, polycystic ovarian syndrome) 
• Mechanical trauma
• Cosmetics
• Topical corticosteroids 
• Oral medications (corticosteroids, lithium, iodides, antiepileptic medications)

Diagnosis

To diagnose acne vulgaris, a thorough history and examination are fundamental.

History and examination

• Areas with increased pilosebaceous glands –face, chest, back
• Clinical course – related to beginning puberty and women may note relation to menstrual cycle
• Lesions:
  • Closed comedones (‘whiteheads’ – non-inflammatory)
  • Open comedones (‘blackheads’ – non-inflammatory)
  • Papules and pustules – superficial raised lesions with or without pus (inflammatory)
  • Nodules or cysts – deeper, palpable, >5mm (inflammatory)
    • Often tender
• Pigmentation – post-inflammatory hyperpigmentation is very common in darker skin types
• Scarring – various types including atrophic, ice-pick or hypertrophic; keloid scarring may result, usually on the torso
• Severity
  • Mild – mostly non-inflamed lesions (open and closed comedones) with few papules and pustules
  • Moderate – more comedones, papules and pustules than in mild. Sometimes truncal involvement along with face.
  • Severe – widespread comedones, papules, pustules, nodules, or cysts. Areas include face, chest and back. Scarring and hyperpigmentation may be present.
  • Very severe – nodulocystic acne and acne conglobata with severe lesions; many large, painful nodulopustular lesions along with papules, pustules and comedones
• Acne fulminans – rare acne subtype presenting with systemic features including fever, arthralgia, myalgia, hepatosplenomegaly and osteolytic bone lesions

 Image Source: Wikimedia Commons (2015). AcneVulgaris on a very Oily Skin, Licensed under a creative commons licence. Available for free at: https://en.m.wikipedia.org/wiki/File:Acne_vulgaris_on_a_very_oily_skin.jpg (Accessed 23 May 2025).

Management 

Treatment is based on the severity and usually a combination of medications are needed to treat acne.

• Mild to moderate acne:
  • 12 week course of one of the following
    • Topical adapalene (retinoid) + topical benzoyl peroxide
    • Topical tretinoin (retinoid) + topical clindamycin
    • Topical benzoyl peroxide + topical clindamycin
  • Topical benzoyl peroxide monotherapy if above contraindicated or patient preference
  • Dry or sensitive skin – creams or lotions rather than gels
  • Oily skin – consider less greasy gels
  • If skin irritation occurs with treatment then modify concentration or frequency of application
• Moderate to severe acne:
  • 12 week course of one of the following
    • Topical adapalene (retinoid) + topical benzoyl peroxide
    • Topical tretinoin (retinoid) + topical clindamycin
    • Topical adapalene (retinoid) + topical benzoyl peroxide + oral lymecycline/ doxycycline
    • Topical azelaic acid + oral lymecycline/doxycycline
  • Topical benzoyl peroxide monotherapy if above contraindicated or patient preference
  • Trimethoprim/oral macrolide (erythromycin) if contraindication or not tolerated oral lymecycline/doxycycline.
  • Combined oral contraceptive + topical agents (if systemic antibiotics not tolerated in women)
    • Useful in women with hormonal involvement for acne (acne related to menstrual periods, ovarian/adrenal hyperandrogenism and polycystic ovary syndrome)
    • Third and fourth generation combined oral contraceptives
    • Co-cyprindol or other ethinylestradiol/cyproterone acetate-containing products
    • Discontinue 3 months after acne controlled
  • Spironolactone
    • Used for its anti-androgenic effects for women only
    • Useful to limit use of long-term antibiotics or for individuals who prefer not to take isotretinoin
    • Contraindicated in pregnancy
  • Oral isotretinoin
    • Indicated in severe or scarring disease, or if insufficient response to other treatment or rapid relapse on stopping it; also in cases with marked psychosocial impact
    • Extremely effective
    • Potently teratogenic; women of child-bearing potential must be enrolled on to a pregnancy prevention programme
    • Common adverse effects comprise mucocutaneous dryness; reports of effects on mental health (e.g. depression, irritability) and sexual dysfunction
• Pregnant women
  • Safe topical agents – azelaic acid, benzoyl peroxide, clindamycin, erythromycin
  • Erythromycin can be used in pregnancy if systemic treatment is clearly required