Acne Vulgaris

Acne Vulgaris

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Acne vulgaris is a common dermatological disorder of the pilosebaceous unit. It is characterized by pustules, papules and comedones and can cause significant psychosocial impact. It affects 80-90% of adolescents regardless of ethnicity. Men and women are equally affected, although men tend to have more severe symptoms. Acne can begin in childhood and persist into adulthood, but these forms are not covered here.



Acne is the result of a multifactorial process, involving increased sebum production, bacterial colonization (P. acnes), and inflammatory mediators due to innate immune system activation. It has a strong heritability, particularly among those with severe phenotypes.


Risk Factors

Precipitating Factors

Acne is typically precipitated by hormonal shifts during puberty, but can also be precipitated or exacerbated by hormonal imbalances leading to excess androgens, such as polycystic ovarian syndrome or congenital adrenal hyperplasia. Exogenous androgens, such as steroids or testosterone, can have a similar effect.

Exacerbating Factors

Acne can be exacerbated by certain medications, including steroids, antiepileptics, and EGRF inhibitors. It can also be worsened by occlusion of the pilosebaceous unit, such as due to topical skin products or cosmetics. High glycaemic index foods and dairy, albeit weakly, have been associated with worsening of symptoms. Chemical exposure can also cause occupational acne.

Relieving Factors

Acne may improve with a low-glycaemic load diet. Avoidance of comedogenic cosmetics and products may also improve symptoms.


Clinical Features


Patients typically report the onset of acne during early puberty, around 12-17 years of age. Some may even have an earlier onset. Female patients may notice cyclical worsening and improvement of symptoms as part of their menstrual cycle. It is important to consider lifestyle factors, medications, and family history when taking a history. Additionally, it is important to ascertain what treatments the patient has tried before.

Clinical Examination

Acne typically affects the face, chest, and upper back but can appear on any skin site with sebaceous glands. Mild (non-inflammatory) acne is characterized by closed comedones (“whitehead”) and open comedones (“blackhead”). Severe, inflammatory acne may involve papules (small, elevated, solid inflammatory lesions that appear erythematous), pustules (small, well-circumscribed, erythematous epidermal lesions filled with pus), nodules (similar to papules but larger than 1 cm), and cysts (firm, encapsulated lesions containing fluid or fluid-like material). After inflammatory acne lesions have healed, there may be remaining signs, including scarring, pigmented macules (small spots less than 1 cm in diameter that are altered in colour), and keloid scarring (shiny, rubbery nodules of fibrous scar tissue).

Forehead Acne in a South-Asian Woman

Acne Vulgaris is the most common form of acne affecting teens, and it has varying clinical presentations depending on the patient's ethnicity. Patients with darker skin may have a lower risk of severe nodulocystic acne than Caucasian patients but a higher risk of post-inflammatory hyperpigmentation and keloid scarring.2

Associated Conditions

Polycystic Ovarian Syndrome (PCOS) is the most common endocrinopathy in women, affecting 15-20% of women. PCOS leads to an increase in free androgens, which exacerbate acne.

Differential Diagnoses

  • Acne Rosacea

Acne rosacea has similarities such as presenting with papules and sometimes pustules, and affecting the face (typically the central face). However it also has differences such as presenting with more generalised erythema and occasionally telangiectasias and tends to affect older women (30's-50's).


Acne is usually diagnosed clinically and often does not require further investigations.

Microscopy and Culture

If a patient has persistent or unusual acne, a skin swab for microscopy and culture may be indicated. For female patients with severe or persistent acne, further testing for underlying hormonal disorders may be required.


Topical Therapies

Mild and moderate acne may be treated with topical therapies. These include salicylic acid, a keratolytic that unblocks pores by removing keratin plugs, and benzoyl peroxide which has antibacterial effects and is available in gel or wash formations at strengths of 2.5-10%. Topical retinoids, which inhibit sebum production, are usually prescribed in low strengths or for use on alternate days as they can be initially irritating to the skin due to their drying effect. Due to its teratogenic properties, topical retinoids should not be prescribed to women who are trying to conceive, are pregnant or are breastfeeding.

Systemic Therapies

Anti-androgenic options for mild to moderate acne in women include the oral contraceptive pill and spironolactone. The oral contraceptive pill that is most effective in treating acne contains cyproterone acetate and anti-androgenic progesterone, and can take more than 6 months for the anti-acne effect to take effect. Spironolactone, a diuretic and anti-androgen, is only indicated for the treatment of acne in women and is contraindicated in pregnancy.


Oral antibiotics such as tetracyclines (doxycycline or minocycline) and erythromycin, used for their anti-inflammatory effects in low doses, can treat moderate acne.


Isotretinoin is highly effective in treating moderate to severe acne, being a systemic retinoid that inhibits sebum production. Side effects include mucosal dryness, dry skin and sensitivity to sun exposure, and regular monitoring of LFTs and cholesterol is important during treatment. As with all retinoids, isotretinoin is teratogenic and should not be prescribed during pregnancy.

Other Therapies and General Management

Patients should be advised to use skincare products that are 'non-comedogenic' or 'non-acnegenic', including gentle non-soap cleansers. A low glycaemic index diet and avoiding picking or scratching at acne lesions can also be beneficial. There are numerous anti-acne products available on the market, some of which are expensive.


Post-inflammatory lesions associated with acne, such as scarring and hyperpigmentation, may persist after the original acne lesion has healed and in some cases may be permanent. Treatment options for acne scarring include fillers and laser therapy. Acne can also have significant mental health implications, such as feelings of self-consciousness and low self-esteem, and can be a contributing factor to depression in severe cases.

Consider Psychosocial Burden of Acne During Holistic Assessment

It is important to consider the psychosocial burden of acne as part of a holistic assessment.

Key Points

  • Acne is the most common dermatological condition, with more than 80% of adolescents suffering from it. Though it is not harmful, it may have a significant psychological and social impact.
  • The form of acne depends on the individual, with open and closed comedones, papules, pustules and cysts occurring. The face, chest, and upper back are typically the most affected areas.
  • Hormonal changes associated with puberty can trigger or worsen acne. Hormonal conditions, such as polycystic ovarian syndrome, may also contribute.
  • Treatments for acne vary depending on the severity of the condition and can include topical and systemic therapies.


  1. British Association of Dermatologists. Handbook for Medical Students and Junior Doctors. 2020. LINK
  3. Bhate & Williams. Epidemiology of acne vulgaris. 2012. LINK
  5. Spencer et al. Diet and acne: A review of the evidence. 2009. LINK
  7. DermNet NZ. Acne. 2014. LINK

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