Overview
Acne Vulgaris
1. Clinical Overview
Summary
Acne vulgaris is the most common skin disorder worldwide, affecting up to 85% of adolescents and young adults. It is a chronic inflammatory condition of the pilosebaceous unit, characterised by comedones, papules, pustules, and in severe cases, nodules and cysts. The pathogenesis involves four key factors: excess sebum production, follicular hyperkeratinisation, Cutibacterium acnes colonisation, and inflammation. Acne can cause significant scarring and profound psychological impact. Treatment is guided by severity, ranging from topical retinoids to oral isotretinoin for severe or scarring disease.
Key Facts
- Definition: Chronic inflammatory disorder of the pilosebaceous unit
- Prevalence: Affects ~85% of people aged 12-24; can persist into adulthood (~10-15% of adults)
- Mortality/Morbidity: No mortality; significant morbidity from scarring (affects up to 95% of acne patients) and psychological impact
- Key Management: Topical retinoids (first-line); oral antibiotics (moderate); isotretinoin (severe/scarring)
- Critical Threshold: Scarring = indication for early aggressive treatment or isotretinoin
- Key Investigation: Clinical diagnosis; hormonal workup if hyperandrogenism suspected
Clinical Pearls
"No Antibiotic Monotherapy": Oral antibiotics should ALWAYS be combined with topical benzoyl peroxide or retinoid to reduce antibiotic resistance — never prescribe alone.
Isotretinoin Teratogenicity: Isotretinoin is absolutely contraindicated in pregnancy. All females must be on a pregnancy prevention programme with monthly pregnancy tests before prescription.
Scarring = Escalate Early: If scarring is present or imminent, escalate treatment early. Scars are permanent; acne is treatable.
Why This Matters Clinically
Acne is not merely cosmetic — it profoundly affects quality of life, self-esteem, and mental health. Depression and anxiety are significantly more common in acne patients. Permanent scarring occurs in up to 95% of cases to some degree, making early effective treatment essential to prevent lifelong impact.
2. Epidemiology
Incidence & Prevalence
- Incidence: Peaks in adolescence; 85-90% of teenagers experience some degree of acne
- Prevalence: Commonest skin disease in the world; affects ~9.4% globally at any given time
- Trend: Increasing adult-onset acne, particularly in women
Demographics
| Factor | Details |
|---|---|
| Age | Peak onset 12-24 years; can persist/develop in adulthood (adult female acne increasingly common) |
| Sex | Adolescence: Male > Female severity; Adulthood: Female > Male prevalence (hormonal acne) |
| Ethnicity | Affects all ethnicities; post-inflammatory hyperpigmentation more prominent in skin of colour |
| Geography | Worldwide; low prevalence in non-Westernised societies (dietary/environmental hypothesis) |
Risk Factors
Non-Modifiable:
- Genetic predisposition (family history strongest predictor)
- Male sex during adolescence
- Hormonal changes (puberty, menstrual cycle)
Modifiable:
| Risk Factor | Relative Risk |
|---|---|
| High glycaemic index diet | 1.2-1.5 |
| Dairy consumption (especially skimmed milk) | 1.2-1.4 |
| Obesity | 1.1-1.3 |
| Use of comedogenic cosmetics/products | Variable |
| Stress | Exacerbating factor |
| Smoking | 1.2-1.3 |
Hormonal Associations:
| Condition | Notes |
|---|---|
| Polycystic ovary syndrome (PCOS) | Common association; consider if persistent adult female acne with hirsutism/menstrual irregularity |
| Congenital adrenal hyperplasia | Rare; early onset severe acne |
| Drug-induced (androgens, corticosteroids, lithium) | Acneiform eruption |
3. Pathophysiology
Mechanism
Step 1: Increased Sebum Production
- Androgens (testosterone, DHT) stimulate sebaceous glands
- Puberty: Sebaceous gland activity increases dramatically
- Sebum provides nutrient substrate for Cutibacterium acnes
Step 2: Follicular Hyperkeratinisation
- Abnormal keratinisation of the infundibulum (upper follicle)
- Keratin accumulates, blocking the follicular opening
- Results in microcomedone formation (precursor lesion)
Step 3: Cutibacterium acnes Colonisation
- C. acnes (formerly Propionibacterium acnes) is a commensal anaerobe
- Thrives in the sebum-rich, hypoxic environment of blocked follicles
- Produces lipases, proteases, and pro-inflammatory factors
- Triggers innate immune response
Step 4: Inflammation
- C. acnes activates Toll-like receptor 2 (TLR2) on keratinocytes
- Release of pro-inflammatory cytokines (IL-1, IL-8, TNF-α)
- Neutrophil recruitment → pustule formation
- Chronic inflammation → nodules, cysts, scarring
Classification
| Severity | Lesion Types | Description |
|---|---|---|
| Mild | Comedones, few papulopustules | Predominantly blackheads/whiteheads; <20 lesions |
| Moderate | Papules, pustules, some nodules | Inflammatory lesions dominate; 20-100 lesions |
| Severe | Nodules, cysts, widespread | Deep painful nodules; conglobata/fulminans; scarring |
| Lesion Type | Description |
|---|---|
| Open comedone (blackhead) | Dilated follicle with melanin-oxidised keratin plug |
| Closed comedone (whitehead) | Blocked follicle with intact surface; precursor to inflammation |
| Papule | Raised, inflamed, <5mm, no visible pus |
| Pustule | Raised, inflamed, visible pus (whitehead) |
| Nodule | Deep, firm, painful lump >mm |
| Cyst | Deep, pus-filled cavity; often recurrent |
Anatomical/Physiological Considerations
The pilosebaceous unit consists of the hair follicle, sebaceous gland, and arrector pili muscle. Sebaceous glands are most dense on the face, chest, and back — hence the distribution of acne. The infundibulum (upper part of the follicle) is the site of hyperkeratinisation. Acne scarring occurs when inflammation extends into the dermis and disrupts normal collagen architecture.
4. Clinical Presentation
Symptoms
Typical Presentation:
Atypical Presentations:
Signs
Red Flags
[!CAUTION] Red Flags — Urgent specialist referral if:
- Acne fulminans: Sudden severe nodular acne with fever, ulceration, arthralgia (emergency isotretinoin + steroids)
- Severe psychological distress: Depression, anxiety, body dysmorphic disorder, suicidal ideation
- Rapid onset of severe acne: May indicate underlying hormonal cause (PCOS, CAH, androgen-secreting tumour)
- Signs of hyperandrogenism in females: Hirsutism, deepening voice, clitoromegaly (hormonal workup required)
- Suspected isotretinoin side effects: Severe mood changes, visual disturbances, persistent headache
Comedones (blackheads and whiteheads) on face/chest/back (100% of cases)
Common presentation.
Inflammatory papules and pustules (60-80%)
Common presentation.
Greasiness of skin (seborrhoea) (70-80%)
Common presentation.
Tender, deep nodules/cysts (10-20% — severe acne)
Common presentation.
Pain and tenderness over inflammatory lesions
Common presentation.
5. Clinical Examination
Structured Approach
General:
- Assess skin type (oily, dry, combination)
- Assess extent: Face, neck, chest, back
- Note psychosocial impact (patient affect, concern level)
Specific Skin Examination:
- Count and document lesion types: Comedones, papules, pustules, nodules, cysts
- Assess scarring: Type (ice-pick, boxcar, rolling), extent
- Note post-inflammatory changes: PIH, PIE
- Check for signs of hormonal acne (distribution along jawline, lower face in females)
Special Tests
| Test | Technique | Positive Finding | Sensitivity/Specificity |
|---|---|---|---|
| Lesion counting | Count inflammatory and non-inflammatory lesions | Used for severity grading (Leeds scale, Global Acne Grading System) | Standardised grading |
| Hormonal workup (females) | LH, FSH, free testosterone, SHBG, DHEAS, fasting glucose | Elevated androgens, LH:FSH ratio > | Screening for PCOS, CAH |
| Wood's lamp | Examine under UV light | Orange fluorescence (C. acnes porphyrins) | Adjunct; not diagnostic |
| Skin biopsy | Rarely needed | Histopathology of pilosebaceous inflammation | Reserved for atypical presentations |
6. Investigations
First-Line (Bedside)
- Clinical diagnosis — no routine investigations needed for straightforward acne
- History: Menstrual history, medications, family history, previous treatments, psychological impact
Laboratory Tests
| Test | Expected Finding | Purpose |
|---|---|---|
| Hormonal profile (females with atypical features) | Elevated free testosterone, DHEAS, LH:FSH >:1 | Screen for PCOS, late-onset CAH |
| Pregnancy test | Negative | Mandatory before and during isotretinoin |
| LFTs (if isotretinoin) | Normal baseline | Monitor for hepatotoxicity |
| Fasting lipids (if isotretinoin) | Normal baseline | Monitor for hypertriglyceridaemia |
| FBC | Normal | Rare: Rule out acne fulminans-associated anaemia |
Imaging
| Modality | Findings | Indication |
|---|---|---|
| Pelvic USS | Polycystic ovarian morphology | If PCOS suspected |
| Adrenal imaging (CT/MRI) | Adrenal mass | If androgen-secreting tumour suspected (very rare) |
Diagnostic Criteria
Clinical Diagnosis:
- Presence of comedones (open or closed) — pathognomonic
- Plus: Papules, pustules, nodules, cysts, scarring
- Distribution: Face, chest, back (sebum-rich areas)
Grading (Global Acne Grading System):
| Grade | Description |
|---|---|
| Mild | Few comedones, few papules |
| Moderate | Many comedones, papules, few pustules |
| Moderately severe | Numerous comedones, papules, pustules, few nodules |
| Severe | Numerous nodules, cysts; scarring |
7. Management
Management Algorithm
Acute/Emergency Management (if applicable)
Acne Fulminans:
- Urgent dermatology referral
- Oral corticosteroids (prednisolone 0.5-1 mg/kg/day) to control inflammation
- Introduce isotretinoin at low dose after 2-4 weeks of steroids
- Supportive care (analgesia, wound care)
Conservative Management
- Gentle skin cleansing (non-comedogenic, pH-balanced cleanser) twice daily
- Avoid picking/squeezing lesions (increases scarring)
- Non-comedogenic, oil-free moisturisers if skin dry
- Sun protection (especially if using retinoids — photosensitivity)
- Dietary advice: Consider reducing high-GI foods, dairy (low-evidence but patient-driven)
- Manage expectations: Improvement takes 6-12 weeks
Medical Management
| Drug Class | Drug | Dose | Duration |
|---|---|---|---|
| Topical Retinoid | Adapalene 0.1% | Apply OD at night | Long-term (maintenance) |
| Topical Retinoid | Tretinoin 0.025-0.1% | Apply OD at night | Long-term |
| Topical Antimicrobial | Benzoyl peroxide (BPO) 2.5-5% | Apply OD or BD | Long-term; reduces resistance |
| Topical Combination | Adapalene/BPO (Epiduo) | Apply OD at night | First-line combination |
| Topical Antibiotic | Clindamycin 1% | Apply BD (ALWAYS with BPO or retinoid) | Short-term only |
| Oral Antibiotic | Lymecycline 408mg OD | Once daily | 3-6 months max |
| Oral Antibiotic | Doxycycline 100mg OD | Once daily | 3-6 months max |
| Oral Retinoid | Isotretinoin 0.5-1 mg/kg/day | Daily with fatty meal | 16-24 weeks (cumulative 120-150 mg/kg) |
| Hormonal (females) | Co-cyprindiol (Dianette) | OD (as oral contraceptive) | 3-6 months; switch to alternative OCP |
| Hormonal (females) | Spironolactone 50-200mg | Once daily | Long-term for hormonal acne |
8. Deep Dive: Isotretinoin (Roaccutane)
The "Nuclear Option".
- Mechanism: Vitamin A analogue. The ONLY drug that targets all 4 pathogenic factors:
- Shrinks sebaceous glands (by 90%).
- Stops hyperkeratinisation.
- Kills C. acnes (by removing sebum food source).
- Anti-inflammatory.
- Indication: Severe nodulocystic acne, or ANY acne causing scarring, or acne refractory to 2 antibiotics.
- Dose: 0.5 - 1.0 mg/kg/day. Cumulative target 120-150 mg/kg (to prevent relapse).
- Pregnancy Prevention Programme (PPP):
- Teratorgenic: Causes severe birth defects (craniofacial, cardiac, CNS).
- Rules: Two forms of contraception. Monthly pregnancy tests. Prescription only valid for 7 days.
- Side Effects:
- Dryness: Cheilitis (dry lips) in 100% of patients. Dry eyes. Dry blood (epistaxis).
- Mood: Rare link to depression/suicide. (Controversial, as acne causes depression too).
- Lipids: Raises triglycerides.
- Liver: Transaminitis.
9. Technical Appendix: Scar Types & Management
"Prevention is better than cure." Treating scars is difficult, expensive, and rarely 100% effective.
1. Atrophic Scars (Loss of tissue)
- Ice Pick (60-70%): Deep, narrow (<2mm) pits. Extend into dermis/subcutis. "V" shape.
- Tx: TCA CROSS (high conc acid), Punch Excision. Lasers fail (too deep).
- Boxcar (20-30%): Round/oval depressions with sharp vertical edges. "U" shape.
- Tx: Subcision, Punch Elevation, Laser Resurfacing.
- Rolling (15-25%): Broad depressions with sloppy edges. "M" shape.
- Tx: Subcision (cut the fibrous tethers pulling skin down). Fillers.
2. Hypertrophic / Keloid (Excess tissue)
- Hypertrophic: Raised, within border of injury.
- Keloid: Extends beyond border. Often jawline/chest/back.
- Tx: Intralesional Steroid (Triamcinolone) injections. Cryotherapy. Silicon gel sheets.
10. Deep Dive: The Hormonal Approach
For the persisting female adult acne.
Spironolactone
- Mechanism: Aldosterone antagonist (diuretic) AND Androgen Receptor Blocker.
- Use: Off-label for acne.
- Effect: Reduces sebum production significantly.
- Side Effects: Diuresis, hyperkalaemia, feminisation of male fetus (Must use contraception), breast tenderness.
Co-Cyprindiol (Dianette)
- Mechanism: Contains Cyproterone Acetate (Anti-androgen).
- Risk: Higher VTE risk than standard OCP.
- Course: Stop 3-4 months after acne clears.
11. Rehabilitation: The Psychology of Acne
"It's just spots" - No, it isn't.
- Suicide Risk: Increased in established severe acne.
- Body Dysmorphic Disorder (BDD): Patient perceives defect as catastrophic. Checks mirrors constantly or avoids them completely.
- Social Isolation: Avoiding school/work during flares.
- Clinician Role: validates the distress. "I can see this is affecting you." Early aggressive treatment IS psychiatric prevention.
Surgical/Procedural Management
Indications:
- Persistent comedones despite medical therapy → comedone extraction
- Acute inflamed cyst → intralesional triamcinolone injection
- Post-acne scarring → laser resurfacing, microneedling, subcision, chemical peels
Procedures:
| Procedure | Purpose |
|---|---|
| Comedone extraction | Remove stubborn comedones |
| Intralesional steroid (triamcinolone 2.5-5 mg/mL) | Rapid reduction of inflamed cysts |
| Chemical peels (glycolic acid, salicylic acid) | Adjunct for mild acne, PIH |
| Fractional laser resurfacing | Atrophic scarring |
| Microneedling | Atrophic scarring |
| Subcision | Ice-pick and boxcar scars |
Disposition
- Refer if: Severe nodulocystic acne, scarring, failed first-line treatment, psychological impact, suspected hormonal cause
- Discharge if: Mild-moderate, responsive to topical treatment
- Follow-up: Review at 8-12 weeks to assess response
8. Complications
Immediate (Minutes-Hours)
| Complication | Incidence | Presentation | Management |
|---|---|---|---|
| Contact dermatitis from topicals | 5-10% | Erythema, pruritus, dryness | Reduce frequency; change formulation |
| Skin dryness/irritation (retinoids) | 30-50% | Peeling, erythema, burning | Reduce frequency; moisturise |
Early (Days-Weeks)
- Post-inflammatory hyperpigmentation (PIH): Brown discolouration; fades with time, sun protection, topical agents
- Post-inflammatory erythema (PIE): Red/pink marks; fades slower; laser can accelerate
- Flare with retinoid initiation: Common in first 2-4 weeks; counsel patient to persist
Late (Months-Years)
- Atrophic scarring: Ice-pick, boxcar, rolling scars — permanent without procedural treatment
- Hypertrophic/keloid scarring: Raised, thickened scars — more common in dark skin, chest/back
- Psychological sequelae: Depression, anxiety, body dysmorphic disorder, social withdrawal
- Relapse after isotretinoin: 20-30% may require second course
9. Prognosis & Outcomes
Natural History
Without treatment, acne typically peaks in adolescence and naturally improves in the early-to-mid 20s. However, 10-15% of adults continue to experience acne, particularly females with hormonal patterns. Scarring occurs in up to 95% of acne patients to some degree and is permanent.
Outcomes with Treatment
| Variable | Outcome |
|---|---|
| Resolution with topical therapy | 60-70% improvement in mild-moderate acne |
| Resolution with oral antibiotics | 60-80% improvement |
| Resolution with isotretinoin | 80-95% long-term remission after one course |
| Scarring | Occurs in up to 95%; early aggressive treatment reduces risk |
Prognostic Factors
Good Prognosis:
- Early treatment before scarring
- Good adherence to topical regimen
- Response to first-line therapy
- No family history of severe acne
Poor Prognosis:
- Delayed presentation with established scarring
- Nodulocystic subtype
- Family history of severe acne
- Truncal acne (harder to treat, more scarring)
- Non-adherence to treatment
10. Evidence & Guidelines
Key Guidelines
- NICE NG198: Acne Vulgaris: Management (2021) — Recommends topical retinoid + BPO as first-line; limits oral antibiotic courses to 3 months; early isotretinoin for scarring or severe disease. NICE
- European Evidence-Based (S3) Guideline for Treatment of Acne (2016) — Comprehensive grading of treatments; strong recommendation for isotretinoin in severe/refractory acne. JEADV
Landmark Trials
Adapalene-BPO Combination Study (Thiboutot et al., 2007) — Established efficacy of fixed-dose adapalene + BPO.
- 517 patients randomised
- Key finding: Adapalene-BPO superior to either monotherapy; 50% reduction in lesions at 12 weeks
- Clinical Impact: Combination therapy became first-line standard
Isotretinoin Meta-analysis (Layton & Henderson, 2022) — Systematic review of isotretinoin outcomes.
- 50+ studies included
- Key finding: 80-95% long-term remission; ~20% require second course
- Clinical Impact: Supports early isotretinoin for severe/scarring acne
Evidence Strength
| Intervention | Level | Key Evidence |
|---|---|---|
| Topical retinoid + BPO (first-line) | 1a | Multiple RCTs; NICE, EDF guidelines |
| Oral antibiotics + topical combo | 1b | RCTs; max 3-6 months |
| Isotretinoin for severe acne | 1a | Meta-analyses; systematic reviews |
| Hormonal therapy (females) | 1b | RCTs for co-cyprindiol, spironolactone |
| Procedural scar treatment | 2a | Case series; expert consensus |
11. Patient/Layperson Explanation
What is Acne?
Acne is a common skin condition that happens when the oil glands in your skin get blocked and inflamed. It causes spots, pimples, and sometimes painful lumps (cysts). Almost everyone gets acne at some point, especially during the teenage years, but it can happen at any age.
Why does it matter?
Acne is not just a cosmetic problem — it can:
- Leave permanent scars if not treated properly
- Affect your confidence and how you feel about yourself
- Cause anxiety or depression in some people
- The good news: Effective treatments exist for all types of acne
How is it treated?
- Creams and gels (topical treatments): The first step — usually a combination of a retinoid (helps unclog pores) and benzoyl peroxide (kills bacteria). Apply at night; expect some dryness initially.
- Antibiotic tablets: For more stubborn acne; usually for 3-6 months alongside creams.
- Isotretinoin (Roaccutane): A powerful tablet for severe or scarring acne. Very effective but requires specialist supervision and monitoring.
- Hormonal treatments: Options for women with hormonal acne (along jawline).
What to expect
- Treatments take 6-12 weeks to work — be patient
- Your skin may get slightly worse before it gets better (especially with retinoids)
- Most people see significant improvement with proper treatment
- Maintenance treatment may be needed to prevent recurrence
When to seek help
- Urgent: If acne suddenly becomes very severe with fever or joint pain (acne fulminans — rare but serious)
- Soon: If you're getting scars, if treatment isn't working after 3 months, or if acne is affecting your mood or confidence
- Routine: Follow-up as advised to monitor progress
12. References
Primary Guidelines
- NICE. Acne vulgaris: management (NG198). National Institute for Health and Care Excellence. 2021. NICE
- Nast A, et al. European Evidence-Based (S3) Guideline for the Treatment of Acne. J Eur Acad Dermatol Venereol. 2016;30(8):1261-1268. PMID: 27538194
Key Trials
- Thiboutot D, et al. Adapalene-benzoyl peroxide, a fixed-dose combination for the treatment of acne vulgaris: results of a multicenter, randomized double-blind, controlled study. J Am Acad Dermatol. 2007;57(5):791-799. PMID: 17628650
- Layton AM, et al. A Review on the Treatment of Acne Vulgaris. Int J Womens Dermatol. 2022;8(1):e002. PMID: 35611164
Further Resources
- DermNet NZ: Acne
- British Association of Dermatologists: Acne Patient Information
- UpToDate: Acne vulgaris: Overview of management
13. Examination Focus
Common Exam Questions
1. MRCP / PLAB:
- Q: A 24-year-old female has severe nodulocystic acne. She is currently breastfeeding. What is the most appropriate systemic antibiotic?
- A: Erythromycin (safe in breastfeeding). Tetracyclines (Doxy/Lymecycline) are contraindicated (tooth staining in infant).
2. Dermatology Rotation:
- Q: What are the absolute contraindications to Isotretinoin?
- A: Pregnancy (Teratogenic), Breastfeeding, Severe Hepatic Impairment, Hyperlipidaemia (relative).
3. General Practice:
- Q: A 16-year-old male has been on Lymecycline for 6 weeks with no improvement. What do you do?
- A: Continue. Antibiotics take 3 months (12 weeks) to show max effect. Check compliance. Ensure BPO is being used.
Viva Points
- "Why Benzoyl Peroxide with Abx?": To prevent bacterial resistance. C. acnes resistance to erythromycin/clindamycin is rising. BPO kills by oxidation (no resistance possible).
- "The Tetracycline Rules": Take with full glass of water (oesophagitis risk). Avoid milk/antacids (calcium binds drug). Photosensitivity (burn easily in sun).
- "Acne Fulminans Management": Do NOT start Isotretinoin immediately (it flares it). Start Oral Steroids first to cool it down, then introduce Isotretinoin gently.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists. This content does not constitute medical advice for individual patients.