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.
Definition
Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit characterised by open and closed comedones with variable inflammatory papules, pustules, nodules or cysts, usually affecting the face and upper trunk and sometimes causing pigmentary change, permanent scarring and substantial psychological morbidity.
Epidemiology
Acne is common around puberty and can persist or begin in adulthood. Sebaceous distribution, family predisposition and androgen sensitivity contribute. Adult acne may coexist with PCOS, but acne alone is not diagnostic of hyperandrogenism. Prescribed medicines and self-administered anabolic steroids can contribute in some people (see BNF).
Pathophysiology
Follicular hyperkeratinisation and sebaceous activity create the microcomedone, while Cutibacterium acnes ecology and the host innate and adaptive inflammatory response shape inflammatory lesions. C. acnes is a commensal rather than a simple acquired infection. Follicular rupture and deeper dermal inflammation produce nodules and cysts; prolonged tissue injury and abnormal repair cause atrophic, hypertrophic or keloid scarring and post-inflammatory pigmentary change.
First principles
The microcomedone is the precursor lesion, but acne is not a simple blockage sequence
Follicular keratinocytes, sebum and the follicular opening interact to form a microscopic plug that can become a closed or open comedone. Open comedones look dark because material at the surface is oxidised, not because of dirt. Hyperkeratinisation, sebaceous activity and inflammation overlap rather than occurring as an invariable linear sequence, which explains why one person can have comedones, papules, pustules and nodules at the same time.1,2
Androgens, sebum, Cutibacterium acnes and host inflammation interact
Androgen-sensitive sebaceous glands become more active around puberty. Cutibacterium acnes is a normal commensal, so acne should not be taught as a contagious infection caused simply by bacterial overgrowth. Changes in the follicular environment, microbial community and host inflammatory response all contribute. This also explains why antimicrobial treatment can help but must not be used alone or indefinitely (see BNF).1,2
Depth and duration of inflammation drive permanent consequences
Superficial comedones and small papules are less likely to scar than persistent deep nodules, cysts, interconnected abscesses or sinus tracts. Scarring risk rises with both severity and duration. Post-inflammatory erythema and pigmentary change can also be prominent, especially in darker skin, and psychological distress may be severe even when lesion counts are modest. Treatment urgency therefore depends on scarring, pigmentary change and mental health as well as visible severity.1
Combination treatment targets different processes and protects antibiotics
Topical retinoids reduce comedone formation, benzoyl peroxide is non-antibiotic antimicrobial and anti-inflammatory treatment, azelaic acid treats comedonal and inflammatory acne, and antibiotics reduce susceptible bacteria and inflammation (see BNF). NICE therefore uses fixed combinations or pairs a non-antibiotic topical with an oral antibiotic, while prohibiting topical antibiotic monotherapy, oral antibiotic monotherapy and concurrent topical plus oral antibiotics (see BNF).1,2
Isotretinoin is effective because it acts broadly, but its safety pathway is part of the treatment
Oral isotretinoin reduces sebaceous activity, comedogenesis and inflammation, so it can produce durable control in severe resistant acne (see BNF). It is also highly teratogenic and has important potential mental-health and sexual-function adverse effects. Current UK practice requires specialist expertise, an Acknowledgement of Risk Form, counselling, baseline and follow-up monitoring and a Pregnancy Prevention Programme when relevant. Since January 2026, a second independent prescriber is no longer a regulatory requirement for people under 18; enhanced information, second-opinion choice and audit measures replaced it.1,3,4,5,6
Presentation
Acne usually presents with open and closed comedones plus inflammatory papules and pustules on the face, chest or back. Deep nodules, cysts, interconnected abscesses, scarring, persistent pigmentary change and psychological distress indicate greater clinical impact. Acne fulminans is a sudden severe systemic variant requiring same-day dermatology referral.1,7,8,9
Cardinal features
- Open comedones, or blackheads, and closed comedones, or whiteheads
- Inflammatory papules and pustules in a sebaceous distribution
- Deep tender nodules or cysts in moderate-to-severe disease
- Face, upper chest, shoulders and upper back involvement
- Post-inflammatory erythema or hyperpigmentation and atrophic, hypertrophic or keloid scarring
- A fluctuating course beginning around puberty but sometimes persisting or first presenting in adulthood
Red flags
- Acne fulminans: sudden severe destructive or ulcerating acne with systemic symptoms requires same-day referral to the on-call hospital dermatology team for assessment within 24 hours
- Acne conglobata or nodulo-cystic acne requires referral to a consultant dermatologist-led team or an accredited GP with an Extended Role working in an agreed pathway
- Rapid progression, active scarring or persistent pigmentary change warrants early specialist consideration rather than repeated ineffective topical courses
- Current suicidal ideation, self-harm, severe depression or anxiety, or body dysmorphic disorder requires direct mental-health assessment and escalation according to immediate safety needs
- Abrupt acne with virilisation, marked hirsutism, menstrual disturbance or exposure to an implicated medicine or anabolic steroid suggests an underlying endocrine or medication-related cause
Investigations
Clinical diagnosis, lesion count and impact assessment
Examine lesion type and distribution, record nodules, scarring and pigmentary change, and ask about duration, previous adequate courses, adherence, irritation, pregnancy plans and medicines. NICE describes mild-to-moderate acne as 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. Treat this as a continuum and incorporate scarring and patient impact.
Expected finding: Comedones support acne over rosacea, perioral dermatitis or folliculitis. Deep nodules, conglobate change, scarring or major distress can justify escalation even when a simple lesion count understates severity.
1Psychological and safety assessment
Ask directly about mood, anxiety, social withdrawal, school or work impact, body image, self-harm and suicidal thoughts because psychological harm does not correlate reliably with visible severity. Establish immediate safety and protective support; do not use a score alone to decide whether urgent mental-health care is needed.
Expected finding: Persistent distress or a mental-health disorder can justify dermatology referral at any acne severity. Suicidal intent, self-harm or immediate risk requires urgent mental-health assessment and a needs-based safety plan.
1,7,8,9Targeted assessment for PCOS, hyperandrogenism or a medication trigger
Do not diagnose PCOS or order a broad hormone panel because of acne alone. Ask about menstrual pattern, hirsutism, scalp hair loss, fertility history, rapid onset, virilisation, weight change and prescribed or self-administered substances. If a medical disorder or medicine is likely to contribute, use the condition-specific diagnostic pathway or refer to an appropriate specialist rather than treating an isolated laboratory result (see BNF).
Expected finding: Acne with irregular cycles and clinical hyperandrogenism raises suspicion for PCOS; rapid virilisation or a marked abrupt change needs assessment for another androgen source. Known PCOS with additional hyperandrogenic features may warrant reproductive-endocrinology or other specialist referral.
1,2Pregnancy and contraception assessment before relevant treatment
Before choosing a topical retinoid or oral tetracycline, establish pregnancy and pregnancy-planning status and discuss effective contraception or an alternative because both are contraindicated during pregnancy and when planning pregnancy (see BNF). Oral isotretinoin has a separate compulsory Pregnancy Prevention Programme for anyone who may become pregnant (see BNF).
Expected finding: A person who is pregnant, planning pregnancy or unable to meet the relevant prevention requirements needs a non-retinoid, non-tetracycline treatment plan selected with current BNF advice.
1,10,4,5,2,6Specialist baseline assessment before oral isotretinoin
Confirm severe acne resistant to adequate systemic-antibiotic and topical courses, and document current and previous treatment, medical history, all current and past mental-health issues, relevant social and family history, pregnancy potential and interactions (see BNF). Baseline mental-health assessment includes history of self-harm or mental-health service contact, current wellbeing and acne impact, plus a validated patient-reported outcome measure; ask about sexual-function concerns. 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).
Expected finding: The lead prescriber documents that isotretinoin is indicated and no other appropriate effective treatment remains, completes the current risk documentation and addresses any mental-health, pregnancy or laboratory issue before starting.
1,4,5,6,11Management
| Step | Detail | Source |
|---|---|---|
| Start with realistic skin-care and diet advice | Use a non-alkaline, pH-neutral or slightly acidic synthetic-detergent cleanser twice daily on acne-prone skin. Choose non-oil-based, non-comedogenic moisturiser, sunscreen and make-up, remove make-up at the end of the day and avoid persistent picking or scratching. Explain that acne is not caused by poor hygiene and that NICE found insufficient evidence for a specific acne diet; support a balanced diet without restrictive promises.1 | NICE NG198 |
| Agree one complete 12-week first-line course and prepare for irritation | Choose the regimen with the patient after discussing acne severity, preferences, pregnancy potential, benefits, adverse effects and previous use (see BNF). Explain that visible benefit can take 6 to 8 weeks. To reduce irritation from benzoyl peroxide or a topical retinoid, begin alternate-day or short-contact application and progress to standard application if tolerated (see BNF).1,2 | NICE NG198 and BNF acne treatment summary |
| Use the exact NICE first-line options for mild-to-moderate acne | Offer one 12-week fixed combination: topical adapalene with benzoyl peroxide once daily in the evening, topical tretinoin with clindamycin once daily in the evening, or topical benzoyl peroxide with clindamycin once daily in the evening (see BNF). The first two are NICE options at any severity, while benzoyl peroxide with clindamycin is limited to mild-to-moderate acne. Topical benzoyl peroxide monotherapy is an alternative when the combination options are contraindicated or the person wishes to avoid a topical retinoid or any antibiotic (see BNF).1,2 | NICE NG198 and BNF acne treatment summary |
| Pair moderate-to-severe acne treatment correctly | Offer a 12-week course of either fixed topical adapalene with benzoyl peroxide once daily in the evening plus oral lymecycline or doxycycline once daily, or topical azelaic acid twice daily plus oral lymecycline or doxycycline once daily (see BNF). When those oral tetracyclines are contraindicated or not tolerated, NICE permits substitution with trimethoprim or an oral macrolide, but select the individual alternative using pregnancy status, allergies, interactions, antimicrobial guidance and the current BNF (see BNF).1,2 | NICE NG198 and BNF acne treatment summary |
| Apply pregnancy, breastfeeding and age constraints before prescribing | Topical adapalene and tretinoin are contraindicated during pregnancy and when planning pregnancy as a precaution, despite negligible expected systemic exposure (see BNF). During breastfeeding, use fixed adapalene with benzoyl peroxide cautiously and do not use fixed tretinoin with clindamycin; fixed benzoyl peroxide with clindamycin may be used cautiously during pregnancy or breastfeeding (see BNF). Regimens containing oral lymecycline or doxycycline are not for pregnancy, planning pregnancy, breastfeeding or people under age 12 (see BNF). Offer effective contraception or choose an appropriate alternative. Oral isotretinoin must never be used during pregnancy or breastfeeding and requires the current MHRA Pregnancy Prevention Programme for anyone who may become pregnant (see BNF).1,10,4,5,2,6 | NICE NG198, MHRA retinoid pregnancy advice and current isotretinoin materials |
| Protect antibiotics and review at 12 weeks | Never use topical antibiotic monotherapy, oral antibiotic monotherapy, or a topical antibiotic together with an oral antibiotic (see BNF). At 12 weeks assess improvement and adverse effects. If an oral-antibiotic regimen has completely cleared acne, stop the oral antibiotic and continue the topical treatment; if improved but not clear, consider oral plus topical treatment for up to 12 more weeks (see BNF). Continue any antibiotic-containing regimen beyond 6 months only exceptionally, review every 3 months and stop the antibiotic as soon as possible (see BNF).1,2 | NICE NG198 and BNF acne treatment summary |
| Escalate a non-response according to severity and previous treatment | After an inadequate 12-week response, offer another NICE option for mild-to-moderate acne. For moderate-to-severe acne not yet treated with an oral-antibiotic combination, offer an appropriate oral-antibiotic regimen with a non-antibiotic topical (see BNF). If moderate-to-severe acne has not responded to a regimen containing an oral antibiotic, consider specialist referral. Also consider referral after two completed 12-week courses for mild-to-moderate acne.1,2 | NICE NG198 |
| Use hormonal contraception and PCOS treatment precisely | If a person receiving acne treatment wants hormonal contraception, consider a combined oral contraceptive in preference to a progestogen-only pill, after checking suitability and current BNF advice (see BNF). Do not present this as mandatory acne treatment for every woman. In known PCOS, first use a standard NICE acne regimen; if ineffective, consider adding co-cyprindiol or another combined oral contraceptive, and review co-cyprindiol after 6 months to discuss continuation or alternatives (see BNF). Refer PCOS with additional hyperandrogenic features to an appropriate specialist.1,2 | NICE NG198 and BNF acne treatment summary |
| Use the referral thresholds rather than repeating ineffective treatment | Refer for diagnostic uncertainty, acne conglobata or nodulo-cystic acne. Consider dermatology referral for mild-to-moderate acne after two completed courses, moderate-to-severe acne that has not responded to an oral-antibiotic-containing regimen, acne causing scarring or persistent pigmentary change, or acne of any severity causing persistent psychological distress or a mental-health disorder (see BNF). Consider referral to mental-health services for significant psychological distress or a mental-health disorder, particularly current or past suicidal ideation or self-harm, severe depression or anxiety, or body dysmorphic disorder; immediate risk requires the urgent mental-health pathway. Consider condition-specific referral when an endocrine disorder or medicine is contributing.1,2,7,8,9 | NICE NG198 |
| Treat acne fulminans as a dermatology emergency | Arrange same-day referral to the on-call hospital dermatology team for assessment within 24 hours. Do not start routine community isotretinoin. Specialist management may use systemic corticosteroid treatment and carefully timed isotretinoin to limit inflammatory flare, selected and monitored under the current BNF (see BNF).1,2,6 | NICE NG198 and BNF acne treatment summary |
| Refer severe resistant acne for specialist isotretinoin consideration | Consider oral isotretinoin only for someone older than 12 with severe acne resistant to adequate systemic-antibiotic and topical courses, including nodulo-cystic acne, acne conglobata, acne fulminans or acne at risk of permanent scarring (see BNF). At referral, fully inform the patient and, when appropriate, family or carers about potential benefits and risks, and provide the specialist with current and past medical history, all current and previous mental-health issues and relevant social and family history. The lead prescriber must have systemic-retinoid expertise and confirm that isotretinoin is indicated and no other appropriate effective treatment remains. The previous requirement for two independent prescribers to approve initiation under age 18 was removed in January 2026 and must not be taught as current practice.1,3,4,6 | NICE NG198, NICE April 2026 update and MHRA January 2026 safety update |
| Complete the current isotretinoin consent and monitoring pathway | At an in-person first appointment, discuss expected benefit, common and serious risks, possible persistence of some adverse effects, mental health, sexual function and pregnancy risk; allow time for reflection and questions (see BNF). Complete the current Acknowledgement of Risk Form for every patient, give the patient a copy, the Patient Reminder Card and dermatology contact details, advise the current patient video before treatment and offer a second opinion. For a patient under 18, a parent or guardian should be asked to sign unless the prescriber judges that this is not in the patient's best interests; document the reason. Later follow-up may be remote when appropriate. Monitor mental health with a validated patient-reported outcome measure and ask about sexual function at every follow-up; by the third appointment the sexual-function question may be brief. Tell every patient never to share capsules and not to donate blood during treatment or for 1 month afterwards (see BNF).1,12,4,5,6,11 | NICE NG198 and MHRA January 2026 risk-minimisation measures |
| Prevent isotretinoin interactions and monitor laboratory safety | Do not prescribe isotretinoin concurrently with a tetracycline because the combination is contraindicated and has been associated with intracranial hypertension (see BNF). If symptoms or signs suggest intracranial hypertension, especially severe or persistent headache with nausea or vomiting, visual disturbance or papilloedema, stop isotretinoin immediately and arrange urgent assessment (see BNF). Avoid concurrent vitamin A because of hypervitaminosis A risk and avoid concurrent topical keratolytic or exfoliative anti-acne agents because local irritation may increase (see BNF). Check liver enzymes and fasting lipids before treatment, 1 month after starting and then every 3 months unless more frequent monitoring is clinically indicated (see BNF).6,11 | Current isotretinoin Summary of Product Characteristics and BNF |
| Individualise the specialist isotretinoin dose and course | The standard isotretinoin daily dose is 0.5 to 1 mg/kg (see BNF). Consider less than 0.5 mg/kg daily for someone at increased risk of adverse effects or already experiencing them (see BNF). Usually continue until a cumulative 120 to 150 mg/kg has been reached (see BNF), but consider stopping earlier after an adequate response with no new acne lesions for 4 to 8 weeks (see BNF).1,6 | NICE NG198 and BNF isotretinoin monograph |
| Apply the February 2026 Pregnancy Prevention Programme by risk category | Anyone who may become pregnant enters the Pregnancy Prevention Programme (see BNF). Unless a documented expectation of no pregnancy risk applies, establish effective contraception for at least 4 weeks before the first prescription, continue it without interruption throughout treatment and for 1 month after the last dose (see BNF). All Pregnancy Prevention Programme prescriptions must be dispensed within 7 days of issue (see BNF). Under the current form: a documented expectation of no pregnancy risk requires no contraception or pregnancy testing but must be reconfirmed at each visit; an implant or intrauterine method in place for at least 4 weeks requires a negative test before the first prescription, testing at follow-up and 1 month after stopping, with prescriptions up to 12 weeks once stable; a hormonal pill or injection plus a barrier method requires a negative test before starting, testing at follow-up and 1 month after stopping, with 30-day prescriptions (see BNF). Medically supervised testing may be remote when appropriate. If unprotected sex occurs, stop isotretinoin and seek immediate advice, including about emergency contraception. If pregnancy is suspected, stop immediately. Pregnancy during treatment or within 1 month after the last dose requires prompt referral to a clinician specialising or experienced in teratology.4,12,5,6,11 | MHRA February 2026 Isotretinoin Acknowledgement of Risk Form, current SmPC and BNF |
| Respond actively to mental-health or sexual-function effects during isotretinoin | Tell the patient to seek medical advice promptly if mental health or sexual function changes or worsens. Significant mental-health change requires stopping isotretinoin and seeking help; if mental-health or sexual-function problems are severe, stop treatment and seek urgent medical advice (see BNF). Suicidal intent or self-harm requires immediate safety assessment and urgent specialist mental-health care. Stopping isotretinoin may not by itself resolve symptoms, so arrange appropriate psychiatric, psychological or sexual-health evaluation and report suspected adverse reactions through Yellow Card.1,4,5,7,8,9,6 | NICE NG198, MHRA isotretinoin measures and NICE mental-health guidance |
| Use maintenance only when relapse history justifies it | Explain that maintenance is not always needed. For frequent relapse, consider fixed topical adapalene with benzoyl peroxide; if this is contraindicated or not tolerated, consider topical adapalene, azelaic acid or benzoyl peroxide alone, applying pregnancy constraints to retinoids (see BNF). Review maintenance after 12 weeks and continue appropriate skin care.1,10,2 | NICE NG198 and BNF acne treatment summary |
| Manage relapse and scarring without automatic isotretinoin repetition | After relapse following a successful first-line course, consider another 12-week course of the same treatment or a different NICE option (see BNF). After isotretinoin, treat mild-to-moderate relapse with a standard option; for moderate-to-severe relapse offer a standard 12-week option or re-refer. A second moderate-to-severe relapse after a second isotretinoin course belongs under specialist decision-making. Continue controlling active acne to prevent more scars; refer severe scarring that persists 1 year after acne clearance to a dermatologist-led team with scarring expertise.1,2,6 | NICE NG198 |
Illustrations
Differentials
Rosacea
Central facial flushing, persistent erythema and telangiectasia with papules or pustules but no comedones, usually in an adult.
Bacterial or Malassezia folliculitis
Monomorphic follicular pustules are often itchy or tender and lack comedones; distribution, exposure and targeted sampling in atypical resistant disease help distinguish it.
Periorificial dermatitis
Grouped papules around the mouth, nose or eyes, often sparing the vermilion border and sometimes associated with topical corticosteroid exposure (see BNF).
Hidradenitis suppurativa
Recurrent painful nodules, abscesses, tunnels and scarring in flexural sites such as axillae and groins rather than a comedonal facial or truncal pattern.
Medication- or anabolic-steroid-related acneiform eruption
Abrupt, often monomorphic papules or pustules after a new medicine or androgen exposure, with fewer true comedones and improvement when the trigger can safely be removed (see BNF).
Complications
- Atrophic, hypertrophic or keloid scarring
- Persistent post-inflammatory erythema or hyperpigmentation
- Depression, anxiety, social withdrawal, body dysmorphic disorder, self-harm or suicidal ideation
- Acne conglobata with interconnected abscesses and sinus tracts
- Acne fulminans with systemic illness
- Antimicrobial resistance after inappropriate or prolonged antibiotic exposure
Prognosis
Many people improve with age, but duration is unpredictable and adult persistence is common. Most respond when they complete an appropriate regimen and it is reviewed systematically, while frequent relapse may justify maintenance. Early control of deep inflammation limits new scars, but established scars may persist after active acne clears and severe persistent scarring can require specialist treatment.
Guidelines
- Acne vulgaris: management (NG198) (NICE, 2021)
- Isotretinoin: changes to prescribing guidance and additional risk minimisation measures (MHRA, 2026)
- Self-harm: assessment, management and preventing recurrence (NG225) (NICE, 2022)
References
- NICE, Acne vulgaris: management, recommendations (NG198)Published 25 Jun 2021 | Updated 30 Apr 2026
- BNF, Acne treatment summary
- NICE, Acne vulgaris: management, update information (NG198)Published 25 Jun 2021 | Updated 30 Apr 2026
- MHRA, Isotretinoin: changes to prescribing guidance and additional risk minimisation measuresPublished 22 Jan 2026
- MHRA, Oral isotretinoin Acknowledgement of Risk Form, version 3.0
- BNF, Isotretinoin
- NICE, Self-harm: assessment, management and preventing recurrence (NG225)Published 7 Sept 2022
- NICE, Depression in adults: treatment and management (NG222)Published 29 Jun 2022
- NICE, Depression in children and young people: identification and management (NG134)Published 25 Jun 2019
- MHRA, Oral retinoid medicines: revised and simplified pregnancy prevention educational materials for healthcare professionals and womenPublished 19 Jun 2019
- Electronic Medicines Compendium, Roaccutane 20 mg soft capsules, Summary of Product CharacteristicsUpdated 5 May 2026
- MHRA, Isotretinoin: updates to prescribing guidance and survey of servicesPublished 27 Oct 2025
Evidence checked: 2026-07-29
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.