Dermatology
Acne Vulgaris
Library·Dermatology·Acne
Don't miss
- Acne fulminans - sudden severe nodulocystic with systemic upset
- Hirsutism + irregular periods + acne - PCOS workup
- Scarring acne - refer earlier than later, scarring is preventable not treatable
- Mental-health impact disproportionate to severity - treat aggressively
First-line
- Mild
- Topical adapalene (OTC in NZ) + benzoyl peroxide. Separate AM/PM, every 2nd night to start, judge at 8-12 weeks
- Moderate
- Add topical clindamycin 1% (always with BPO, never alone) ± oral doxycycline 50-100 mg/day for 3 months max
- Pigmentation
- PIH common in Fitzpatrick IV-VI - treat active acne hard, add azelaic acid + sun protection
- Avoid
- Topical fusidic acid (resistance), clindamycin monotherapy, antibiotics >3 months
Refer when
- Severe / nodulocystic / scarring - isotretinoin (Special Authority, dermatologist initiation)
- Failure on optimised topical + 3 months oral antibiotic
- Significant scarring already present
- Acne fulminans or DRESS-like reaction
Tell the patient
- Topicals take 8-12 weeks - judging at 4 weeks is too early
- Treatment continues even when clear - it prevents the next wave
- Picking turns spots into scars
- Diet evidence is mixed; high-glycaemic diets may worsen, dairy is plausible but not proven
Acne results from four converging processes: follicular hyperkeratinisation, excess sebum production under androgen influence, colonisation by Cutibacterium acnes, and the resulting inflammatory cascade. Most presentations in primary care are comedonal (non-inflammatory) or mild-to-moderate papulopustular disease. Nodulocystic acne - deep, painful nodules with significant scarring potential - warrants earlier referral. Grading severity guides treatment choice, but patient distress and the risk of scarring are equally important parameters.
❍ Mild acne: topical retinoids and benzoyl peroxide
Topical retinoids are the cornerstone of mild acne management. Adapalene 0.1% gel is available over-the-counter in New Zealand and is well tolerated relative to older retinoids. It targets follicular hyperkeratinisation (comedonal acne) as well as inflammation. Benzoyl peroxide 2.5-5% reduces C. acnes colonisation without selecting for antibiotic resistance - this distinguishes it from antibiotic-based treatments and makes it a valuable combination partner.
The combination approach: benzoyl peroxide in the morning, adapalene at night. Starting every second night reduces the irritation and dryness that drives early discontinuation. Incorporate a non-comedogenic moisturiser and broad-spectrum SPF 30+ sunscreen from the outset - both retinoids and BP increase photosensitivity and dryness. Advise patients that improvement takes 8-12 weeks and is unlikely to be dramatic in the first month.
❍ Moderate acne: antibiotics and escalation
For multiple papulopustules or early nodules, add topical clindamycin 1%. Always combine with benzoyl peroxide to reduce resistance selection pressure - topical clindamycin monotherapy should not be prescribed. Avoid concurrent oral and topical antibiotics of different classes.
If topical therapy is insufficient after 2-3 months, oral antibiotics are appropriate. Doxycycline 50-100 mg daily is first-line. Limit oral antibiotic courses to 3-6 months; using topical benzoyl peroxide throughout the entire course reduces resistance. Lymecycline is an alternative if doxycycline is not tolerated.
Hormonal therapy is effective for females with cyclical worsening or features of androgen excess (hirsutism, irregular cycles). Combined oral contraceptives containing an anti-androgenic progestogen (drospirenone, norgestimate) reduce sebum production and improve acne. Spironolactone 50-100 mg daily has good evidence for acne in adult women and is particularly useful for those not on the COCP; it requires potassium monitoring (especially with ACE inhibitors or renal impairment) and should not be used in pregnancy.
❍ Severe acne and isotretinoin referral
Nodulocystic acne, significant scarring, or failure of adequate oral antibiotic therapy are the main indications for isotretinoin referral. In New Zealand, oral isotretinoin is a PHARMAC Special Authority medication requiring dermatologist initiation. Refer rather than prolonging inadequate therapy - each month of severe uncontrolled acne carries a cumulative scarring risk.
Isotretinoin is teratogenic. Before initiation, two forms of contraception are required in females of reproductive potential. The prescriber has significant pregnancy prevention obligations under the SA criteria. Document counselling thoroughly if you are involved in ongoing care of a patient on isotretinoin.
Common side effects to counsel on: dryness (skin, lips, eyes, nasal mucosa), sun sensitivity, and initial worsening (acne flare in the first 4-6 weeks is common). Monitoring requirements during isotretinoin include LFTs, lipids, and FBC.
❍ Post-inflammatory hyperpigmentation
Post-inflammatory hyperpigmentation (PIH) - the dark marks left after acne lesions resolve - is particularly pronounced in people with Fitzpatrick skin types IV-VI, which includes many Maori, Pacific, and Asian patients. For some patients, PIH is their primary complaint and more distressing than the active acne itself. This is worth asking about directly, as it changes how you frame the treatment conversation.
Treating active acne aggressively to prevent new lesions is the most effective strategy for PIH. For existing marks: topical azelaic acid 20% (available on prescription) and adapalene both reduce pigmentation over several months. Sun protection is esse