PassFinals
Dermatology

Acne vulgaris

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit that produces comedones and inflammatory lesions; treatment is selected by severity, scarring and psychological impact, with strict antimicrobial stewardship and pregnancy safeguards for retinoids and tetracyclines.

In a nutshell

Acne combines comedones with inflammatory papules, pustules or nodules and is diagnosed clinically. Give one complete 12-week NICE regimen, never use antibiotic monotherapy or topical and oral antibiotics together, and escalate early for nodulo-cystic disease, scarring, persistent pigmentary change or major psychological impact (see BNF). Current isotretinoin safety measures use one expert lead prescriber plus enhanced risk documentation and monitoring, not mandatory approval by two prescribers for under-18s.

Classic presentation

An adolescent has mixed open and closed comedones with inflammatory papules and pustules over the face and upper trunk, sometimes with pigmentary change or early scarring.

Key points

  • Mild-to-moderate acne includes any number of comedones, up to 34 inflammatory lesions or up to 2 nodules; moderate-to-severe acne includes 35 or more inflammatory lesions or 3 or more nodules.
  • First-line fixed combinations are adapalene with benzoyl peroxide or tretinoin with clindamycin at any severity, and benzoyl peroxide with clindamycin only for mild-to-moderate acne (see BNF).
  • For moderate-to-severe acne, pair adapalene with benzoyl peroxide or azelaic acid with oral lymecycline or doxycycline; do not add an oral antibiotic to a topical antibiotic (see BNF).
  • Topical retinoids are contraindicated in pregnancy and when planning pregnancy. Use adapalene with benzoyl peroxide cautiously during breastfeeding, do not use tretinoin with clindamycin during breastfeeding, and use benzoyl peroxide with clindamycin cautiously during pregnancy or breastfeeding. Oral lymecycline or doxycycline regimens are not for pregnancy, planning pregnancy, breastfeeding or people under age 12 (see BNF).
  • Oral isotretinoin is contraindicated during pregnancy and breastfeeding and requires the current Pregnancy Prevention Programme for anyone who may become pregnant (see BNF).
  • Review at 12 weeks: stop the oral antibiotic if clear, or continue oral plus topical treatment for up to 12 further weeks if improving but not clear. Antibiotic treatment beyond 6 months is exceptional and reviewed every 3 months (see BNF).
  • Refer acne conglobata or nodulo-cystic acne, and consider referral for failed adequate courses, scarring, persistent pigmentary change or persistent psychological distress.
  • Acne fulminans requires same-day on-call dermatology referral and assessment within 24 hours.
  • Since January 2026, people under 18 no longer need two independent prescribers to approve isotretinoin initiation; the expert lead prescriber uses enhanced risk documentation, patient information, second-opinion choice and monitoring.
  • During isotretinoin, monitor mental health with a validated patient-reported measure and ask about sexual function at every follow-up. Severe problems require stopping treatment and urgent medical advice (see BNF).
  • Use isotretinoin at 0.5 to 1 mg/kg daily (see BNF), consider less than 0.5 mg/kg daily when adverse effects are likely or occurring (see BNF), and usually target a cumulative 120 to 150 mg/kg (see BNF); an adequate response with no new lesions for 4 to 8 weeks can justify earlier cessation (see BNF).
  • Never combine isotretinoin with a tetracycline because of intracranial-hypertension risk; check liver enzymes and fasting lipids before treatment, 1 month after starting and then every 3 months unless clinically indicated more often (see BNF).
  • Maintenance is not automatic; consider it for frequent relapse and review after 12 weeks (see BNF).

First-line investigation

No routine laboratory test confirms acne: classify lesions and distribution, document scarring and pigmentary change, assess psychological impact and pregnancy potential, and investigate endocrine or medication causes only when clinically suggested.

Management

Recognise emergencies and immediate safety needs

  • Acne fulminans requires same-day referral to the on-call hospital dermatology team for assessment within 24 hours. Specialist treatment may include systemic corticosteroid and carefully timed isotretinoin therapy (see BNF).1,2,6
  • Ask directly about self-harm and suicidal thoughts when distress is present. Immediate risk requires urgent specialist mental-health assessment and a needs-based safety plan, not reassurance based on acne severity or a questionnaire score.1,7,8,9

Classify severity and choose safely

  • Record comedones, inflammatory lesions, nodules, distribution, duration, scarring, pigmentary change, previous complete courses, adherence and psychological impact. Severity is a continuum, so do not let lesion count overrule scarring or distress.1
  • Establish age, pregnancy, pregnancy-planning and breastfeeding status before treatment. Topical retinoids and oral tetracyclines are contraindicated in pregnancy or when planning pregnancy; oral lymecycline or doxycycline regimens are also not for breastfeeding or people under age 12. Use fixed adapalene with benzoyl peroxide cautiously during breastfeeding, do not use fixed tretinoin with clindamycin during breastfeeding, and use fixed benzoyl peroxide with clindamycin cautiously during pregnancy or breastfeeding (see BNF).1,10,2
  • Acne alone does not diagnose PCOS. Ask about menstrual disturbance, hirsutism, virilisation and medication or anabolic-steroid exposure, then use condition-specific investigation or specialist referral when an underlying cause is likely (see BNF).1,2

Give a complete 12-week NICE regimen

  • For mild-to-moderate acne, use fixed adapalene with benzoyl peroxide, fixed tretinoin with clindamycin, or fixed benzoyl peroxide with clindamycin once daily in the evening. Benzoyl peroxide alone is the non-retinoid, non-antibiotic alternative described by NICE (see BNF).1,2
  • For moderate-to-severe acne, combine fixed adapalene with benzoyl peroxide once daily in the evening or topical azelaic acid twice daily with oral lymecycline or doxycycline once daily. Select any tetracycline alternative using current age, pregnancy, breastfeeding and BNF advice (see BNF).1,2
  • Never use topical-antibiotic monotherapy, oral-antibiotic monotherapy, or topical and oral antibiotics together. Start irritating topicals alternate-day or short-contact, then increase if tolerated; explain benefit often takes 6 to 8 weeks (see BNF).1,2

Review response and protect antibiotics

  • Review at 12 weeks. If an oral-antibiotic regimen has cleared acne, stop the oral agent and continue the topical; if improved but not clear, consider oral plus topical therapy for up to 12 more weeks (see BNF).1,2
  • Continue an antibiotic-containing regimen beyond 6 months only exceptionally, with review every 3 months and stopping as soon as possible. An inadequate moderate-to-severe response despite an oral-antibiotic regimen prompts specialist consideration (see BNF).1,2
  • Maintenance is not always required. For frequent relapse consider adapalene with benzoyl peroxide, or if unsuitable a single topical adapalene, azelaic acid or benzoyl peroxide, and review after 12 weeks (see BNF).1,10,2
  • After relapse following first-line success, repeat the same or another NICE course for 12 weeks. After isotretinoin, treat mild-to-moderate relapse with a standard option and treat or re-refer moderate-to-severe relapse; a further moderate-to-severe relapse after a second isotretinoin course remains specialist-owned. Refer severe scars persisting 1 year after acne clearance to a dermatologist-led scar service (see BNF).1,2,6

Refer severe, resistant or high-impact acne

  • Refer diagnostic uncertainty, acne conglobata and nodulo-cystic acne. Consider dermatology referral for failed adequate courses, scarring, persistent pigmentary change or persistent psychological distress. Consider mental-health-service referral for significant distress or disorder, especially current or past suicidal ideation or self-harm, severe depression or anxiety, or body dysmorphic disorder; immediate risk needs urgent mental-health care (see BNF).1,2,7,8,9
  • Isotretinoin is for severe acne in someone older than 12 when adequate systemic-antibiotic and topical courses have failed. At referral, explain benefits and risks and send current and past medical and mental-health history plus relevant social and family history. One expert lead prescriber confirms the indication; mandatory approval by two prescribers for under-18s ended in January 2026 (see BNF).1,3,4,6
  • Before isotretinoin, use an in-person consultation, current Acknowledgement of Risk Form, patient video and Reminder Card, offer a second opinion, assess mental health with a validated outcome measure, ask about sexual function and enrol anyone who may become pregnant into the current Pregnancy Prevention Programme. For a patient under 18, ask a parent or guardian to sign unless this is not in the patient's best interests, and document the reason (see BNF).1,12,4,5,6

Keep isotretinoin monitoring operational

  • At every follow-up, repeat objective mental-health monitoring and ask about sexual function, although the sexual-function check may be brief by the third appointment. Later visits and medically supervised pregnancy tests may be remote when clinically appropriate (see BNF).1,12,4,6
  • Use a standard isotretinoin daily dose of 0.5 to 1 mg/kg (see BNF), or consider less than 0.5 mg/kg daily when adverse effects are likely or occurring (see BNF). Usually target a cumulative 120 to 150 mg/kg (see BNF), with earlier cessation possible after adequate response and no new lesions for 4 to 8 weeks (see BNF).1,6
  • Do not combine isotretinoin with a tetracycline because of intracranial-hypertension risk, avoid concurrent vitamin A, and avoid concurrent topical keratolytic or exfoliative anti-acne agents (see BNF). Severe or persistent headache with nausea or vomiting, visual disturbance or papilloedema suggests intracranial hypertension: stop isotretinoin immediately and arrange urgent assessment (see BNF). Check liver enzymes and fasting lipids before treatment, 1 month after starting and then every 3 months unless clinical circumstances require more frequent monitoring (see BNF).6,11
  • Unless no pregnancy risk is documented, establish effective contraception at least 4 weeks before isotretinoin, continue it throughout treatment and for 1 month after. Dispense every Pregnancy Prevention Programme prescription within 7 days of issue. The February 2026 form then separates no expected risk, implant or intrauterine contraception, and pill or injection plus barrier categories; testing and prescription limits differ, and category C prescriptions remain limited to 30 days (see BNF).4,5,6,11
  • After unprotected sex, stop isotretinoin and seek immediate advice, including about emergency contraception. Suspected pregnancy requires immediate cessation; pregnancy during treatment or within 1 month after the last dose requires prompt specialist teratology advice (see BNF).5,6,11
  • New or worsening mental-health or sexual-function symptoms need prompt medical review. Significant mental-health change, or severe mental or sexual problems, requires stopping isotretinoin and urgent advice; self-harm or suicidal intent activates the immediate mental-health pathway (see BNF).1,4,5,7,8,9,6

Exam traps

  • Do not use an oral antibiotic alone, a topical antibiotic alone, or topical and oral antibiotics together (see BNF).
  • Benzoyl peroxide with clindamycin is a mild-to-moderate option; adapalene with benzoyl peroxide and tretinoin with clindamycin are listed by NICE at any severity (see BNF).
  • Topical retinoids are contraindicated during pregnancy and when planning pregnancy despite low systemic exposure (see BNF).
  • Oral lymecycline and doxycycline acne regimens are not for pregnancy, planning pregnancy, breastfeeding or people under age 12; fixed topical combinations also have product-specific breastfeeding restrictions (see BNF).
  • Do not diagnose PCOS from acne alone or order indiscriminate hormone tests; look for menstrual disturbance and additional hyperandrogenism.
  • Psychological impact can be severe at any visible acne severity and can justify dermatology or mental-health referral.
  • The two-independent-prescriber rule for isotretinoin initiation under age 18 ended in January 2026; second opinion remains an offered patient choice, not mandatory approval.
  • Do not teach universal monthly pregnancy tests and 30-day prescriptions for every isotretinoin patient; the February 2026 form uses pregnancy-risk and contraception categories.
  • Unless no pregnancy risk is documented, establish effective contraception at least 4 weeks before isotretinoin and continue it throughout treatment and for 1 month after the last dose (see BNF).
  • Do not combine isotretinoin with a tetracycline because of intracranial-hypertension risk (see BNF).
  • Standard isotretinoin dosing is 0.5 to 1 mg/kg daily (see BNF), with a lower dose considered for adverse-effect risk or occurrence and a usual cumulative target of 120 to 150 mg/kg (see BNF).
  • Acne fulminans is not routine severe acne: refer the same day to on-call hospital dermatology for assessment within 24 hours.

Illustrations

Comedonal acneClinical photograph showing numerous open and closed comedones across the forehead with a few small inflammatory papules, illustrating mild-to-moderate acne.Roshu Bangal, Wikimedia Commons · CC-BY-SA-4.0
Nodulo-cystic acne with scarringClinical photograph of deep inflammatory nodules and established scarring, showing why duration and depth of inflammation justify early specialist referral.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. NICE, Acne vulgaris: management, recommendations (NG198)Published 25 Jun 2021 | Updated 30 Apr 2026
  2. BNF, Acne treatment summary
  3. NICE, Acne vulgaris: management, update information (NG198)Published 25 Jun 2021 | Updated 30 Apr 2026
  4. MHRA, Isotretinoin: changes to prescribing guidance and additional risk minimisation measuresPublished 22 Jan 2026
  5. MHRA, Oral isotretinoin Acknowledgement of Risk Form, version 3.0
  6. BNF, Isotretinoin
  7. NICE, Self-harm: assessment, management and preventing recurrence (NG225)Published 7 Sept 2022
  8. NICE, Depression in adults: treatment and management (NG222)Published 29 Jun 2022
  9. NICE, Depression in children and young people: identification and management (NG134)Published 25 Jun 2019
  10. MHRA, Oral retinoid medicines: revised and simplified pregnancy prevention educational materials for healthcare professionals and womenPublished 19 Jun 2019
  11. Electronic Medicines Compendium, Roaccutane 20 mg soft capsules, Summary of Product CharacteristicsUpdated 5 May 2026
  12. MHRA, Isotretinoin: updates to prescribing guidance and survey of servicesPublished 27 Oct 2025

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.