Last updated:
March 9, 2026
Table Of Contents
Overview
Acne vulgaris (aka ‘acne’) is a very common disorder of the pilosebaceous follicles (oil glands). It results from excess production of sebum, which is related to androgen (testosterone) levels. It is associated with psychological distress (including depression, anxiety, and social phobia). Early treatment leads to better outcomes and reduces the risk of long-term scarring. The diagnosis is clinical. It is important to remember that acne can be disfiguring, has a large psychological impact, and has the potential for (avoidable) scarring. Cystic acne should be referred to a specialist (dermatologist) to reduce the risk of scarring.
Acne peaks in teenage years (second decade) and may continue into adulthood, where it affects 15% of women and 5% of men.
Lesions seen in acne
| Lesion | Description |
|---|---|
| Obstructed pilosebaceous units. Can cause scarring and lead to cysts. | Indicates hyperkeratinisation. Does not form cysts. |
| Closed comedones (whiteheads) | Small, inflammatory, and usually raised, red lesions |
| Papules (deep) | Fills up within the months after a flare-up. Scarring is fully assessed once the inflammatory phase has resolved. |
| Pustules | More superficial than papules |
| Nodules | Bigger papules |
| Cysts | > 5mm in size. Develops when there is further infection and inflammation by P. acnes. Can be treated with intra-lesion steroids, antibiotics, and isotretinoin |
| Atrophic scars | Fills up within the months after flare-up. Scarring is fully assessed once the inflammatory phase has resolved. |
Acne according to severity
| Severity | Features |
|---|---|
| Mild acne | Open and closed comedones with minimal inflammatory lesions |
| Moderate acne | Widespread non-inflammatory lesions with many papules and pustules |
| Severe acne | Extensive inflammatory lesionsl including nodules, pitting, and scarring |
- Causes of acne
- Androgenic stimulation of the sebaceous gland (increased sensitivity to androgens)
- Polycystic Ovarian Syndrome (PCOS)
- Steroid Use
- Skincare products that increase oil load on the skin e.g. heavy make-up
- Full-fat milk has a slight effect on the development, but there is no clear relation between acne and diet
- Pathophysiology
- Increased sebum production: Sebum production is driven by an increase in androgens. Increased sebum favours the proliferation of skin microorganisms and follicular occlusion.
- Follicular hyperkeratinisation: keratinocytes proliferate and differentiate abnormally within the pilosebaceous unit. This forms a keratinous plug known as a microcomedo (the lesion)
- Colonisation with Propionibacterium acnes: anaerobic bacteria like P. acnes overgrow in the follicle due to increased sebum. They metabolize triglycerides into fatty acids, which attract neutrophils and monocytes.
- Inflammation: the immune system responds to P. acnes by releasing pro-inflammatory cytokines. This leads to inflammation, erythema, and inflammatory lesions (papules, pustules, nodules, and cysts)
- Areas affected by acne
- The face (universal)
- Chest, neck, and back (severe cases)
- Signs and symptoms
- Features of severe acne
- A large number of comedones
- Scarring
- Resistant to basic treatment
- Affects the trunk
- Has a large psychological impact
- Differentials
- Acne Rosacea: occurs later in life. Skin is not greasy, and there are no comedones. Mainly affects the face (cheeks). If the nose is affected, it is most likely rosacea.
- Peri-orificial dermatitis
- Folliculitis: lesions are more uniform than those of acne
- Indications for early referral to a dermatologist (specialist) and isotretinoin treatment
- Concern for severe acne
- Strong family history
- Signs of scarring
- Rapid progression
- Complications of acne
- Post-inflammatory hyperpigmentation (in darker skin types)
- Post-inflamatory erythema (in lighter skin types)
- Scarring
- Nodulocystic lesions
- Secondary infection
- Psychological and social effects, e.g. Depression, Anxiety, social withdrawal, and suicidal ideation
- Antibiotic resistance
- Tetracycline teeth staining
- Side effects of isotretinoin (teratogenicity, hyperlipidaemia, and hepatotoxicity)
Treatment of Acne
Treatment needs to be continued for at least 6 weeks to produce effects. Topical therapies are used for mild acne, oral therapies for moderate-severe acne, and oral retinoids for severe acne
Principles of treating acne
| Principle | Treatment |
|---|---|
| Comedolysis (unblock pores) | Topical benzoyl peroxide, isotretinoin gel, adapalene lotion |
| Decrease bacterial load in sebum | Topical or oral antibiotics |
| Decrease sebaceous gland activity | Isotretinoin (oral), Combined Oral Contraceptives (women only), Spironolactone (women only) |
Treatment according to severity
| Severity | Treatment |
|---|---|
| Mild acne | Topical combination agents |
| Moderate-to severe acne | Topical or systemic (oral) combination agents |
| Severe acne | Systemic (oral) combination agents |
- Conservative management of acne
- Reassurance that acne is often mild and self-limiting
- Wash twice daily with soap and water
- Avoid the use of oily skin products (use cosmetics sparingly)
- Advice that sunlight can increase the risk of scarring/make the scars appear more visible
- Topical combination agents for treating acne
- Benzoyl peroxide (first line)
- Topical antibiotics (clindamycin and erythromycin) + benzoyl peroxide to reduce resistance
- Topical retinoids (adapeline) +/- benzoyl peroxide
- Systemic treatment of acne
- Oral antibiotics
- Tetracycline (doxycycline, minocycline, lymecycline) is the first-line oral antibiotic
- Clindamycin and erythromycin can be used in pregnancy
- Isotretinoin: prescribed by a dermatologist, very effective and teratogenic, contraindicated while using tetracycline (risk of benign intracranial hypertension), and with progesterone only pill (reduces effectiveness and increases the risk of pregnancy)
- Antiandrogens
- Oral Contraceptive Pills, e.g., Dianette (co-cyprindiol), can be used in place of oral antibiotics in women
- Spironolactone (used off-label)
- Oral antibiotics