Acne severity and scarring risk

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit, not a consequence of dirt. Examine clean skin in good light and palpate for depth. Record comedones, papules, pustules and nodules separately, map face and trunk, and distinguish active inflammation from atrophic scars, raised scars and post-inflammatory colour change. Erythema may appear red, violaceous, grey or mainly as swelling and tenderness across different skin tones.

A label such as mild, moderate or severe is useful only when paired with consequences. NICE treatment choices use severity bands, yet rapid scar formation, widespread truncal disease, persistent pigment change and severe distress alter urgency. Ask what the patient most wants improved and whether previous regimens were used for an adequate duration over the whole acne-prone area.

Dietary restriction is not a standard treatment. Explore anabolic steroids, prescribed medicines, occupational occlusion, hair and skin products and possible polycystic ovary syndrome when the history suggests them, without implying blame. Shared planning should include irritation prevention, pregnancy potential, antimicrobial stewardship, realistic timing and an agreed twelve-week review.

Key points

Look for open and closed comedones, inflammatory papules, pustules, nodules, active scars and persistent pigment change across the face, chest and back.
Severity is multidimensional: count and depth of lesions matter, but distribution, scarring trajectory, persistent pigment change and psychological impact can justify earlier escalation.
Mild-to-moderate disease usually has comedones with limited papules or pustules and no nodules; moderate-to-severe disease has many inflammatory lesions or nodules and often truncal involvement.
Nodulocystic acne, acne conglobata, acne fulminans, ongoing scarring or persistent pigmentary change warrants specialist consideration under NICE referral criteria.
Offer a twelve-week evidence-based first-line regimen and review response, adherence, irritation and new scars rather than switching products after only a few days.
Do not use a topical antibiotic, an oral antibiotic, or simultaneous topical and oral antibiotics as acne monotherapy or combination strategy.
Ask directly about mood, social avoidance and self-harm; a mild-looking eruption can have severe personal consequences.
Good photographs require informed consent, consistent lighting and secure handling; colour calibration and palpation reduce under-recognition of inflammation in darker skin.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Androgen-responsive pilosebaceous units

Pubertal and adult androgen signalling increases sebum production in susceptible follicles; circulating androgen concentrations may remain normal despite marked local responsiveness.

Follicular occlusion

Abnormal keratinocyte shedding plugs the infundibulum, initially creating an invisible microcomedone and then an open or closed comedone.

Microbial and inflammatory amplification

Cutibacterium acnes within the lipid-rich follicle activates innate inflammation, but acne is not simply an infection and is neither contagious nor caused by poor hygiene.

Medicines and external factors

Systemic corticosteroids, anabolic steroids, lithium, some antiepileptics, occlusion and comedogenic products can induce or aggravate acneiform eruptions; the morphology and timeline guide causality.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Microcomedone formation
Sebum retention behind a keratin plug distends the follicle; exposure of the plug produces an open comedone, while an intact surface produces a closed comedone.
2
Inflammatory lesion evolution
Follicular wall inflammation generates papules and pustules; deeper rupture releases keratin and lipid into the dermis, producing nodules, cyst-like swellings and tissue destruction.
3
Scar remodelling
Deep or prolonged inflammation distorts collagen repair, causing atrophic ice-pick, rolling or boxcar scars, or raised hypertrophic and keloid scars.
4
Persistent colour change
Inflammation can leave post-inflammatory hyperpigmentation or, less often, hypopigmentation; pigment change may be the dominant visible burden in darker skin even when active erythema is subtle.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Comedonal disease

Open blackheads and closed flesh-coloured or pale bumps demonstrate follicular plugging; black colour reflects oxidised keratin rather than dirt.

Inflammatory burden

Papules and pustules vary from pink-red to violaceous or hyperpigmented; warmth, tenderness and palpable elevation can reveal activity when colour contrast is limited.

Deep nodules

Firm painful lesions extending into the dermis predict tissue injury and make a severity label based only on visible pustule count unsafe.

Early scar formation

New pits, rolling depressions, firm raised plaques or keloids indicate permanent structural change and should accelerate effective treatment and referral consideration.

Endocrine pattern

Irregular menses, infertility, hirsutism, androgenic alopecia, rapid virilisation or sudden adult onset prompts targeted endocrine assessment rather than routine hormone panels for everyone.

Acne fulminansRed flag

Sudden ulcerating or crusted painful nodules with fever, malaise or joint pain require same-day specialist discussion because treatment can differ from ordinary severe acne.

Red flags requiring action

Acne fulminans, systemic illness, rapidly destructive nodules, severe psychological distress, self-harm thoughts, diagnostic uncertainty or an androgenising syndrome require urgent or specialist assessment rather than routine topical escalation.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Structured morphology and distribution recordFirst step
Why
Establish severity, scar trajectory and a reproducible baseline before treatment.
Interpretation and limitations
Record lesion types and sites rather than one total count; photographs add value only with consent, secure storage and comparable lighting.
02
Psychological and functional assessment
Why
Identify distress that changes urgency and treatment acceptability.
Interpretation and limitations
Ask directly about mood, avoidance, bullying and self-harm; a screening score supports but does not replace a safety assessment.
03
Medicine and product reconciliation
Why
Detect acneiform medicines, anabolic steroids and occlusive or comedogenic exposures.
Interpretation and limitations
A temporal relationship supports causality, but do not stop essential prescribed therapy without discussing risk and alternatives with its prescriber.
04
Androgen investigations when clinically indicated
Why
Assess suspected hyperandrogenism or an androgen-secreting disorder.
Interpretation and limitations
Test choice and timing depend on symptoms and menstrual status; rapid virilisation or markedly raised androgens needs urgent specialist evaluation.
05
Microbiology only for an atypical pustular eruption
Why
Investigate suspected bacterial folliculitis or resistant Gram-negative folliculitis rather than routine acne.
Interpretation and limitations
Acne is diagnosed clinically and ordinary pustules do not require swabbing; sample a fresh pustule before further antibiotics when the phenotype has changed.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Rosacea

Central facial flushing, persistent erythema, telangiectasia and papules without comedones favour rosacea; ocular symptoms and trigger-linked burning strengthen that distinction.

Folliculitis

Monomorphic follicle-centred pustules, itch, a shaving relationship or a hot-tub exposure suggest bacterial, yeast-associated or mechanical folliculitis rather than polymorphic acne.

Periorificial dermatitis

Small grouped papules around the mouth, nose or eyes with vermilion-border sparing and topical corticosteroid exposure occur without typical comedones.

Drug-induced acneiform eruption

An abrupt, monomorphic eruption after corticosteroid, testosterone, lithium or another culprit medicine lacks the mixture of comedones and inflammatory lesions expected in acne vulgaris.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Mild to moderate acneStart a complete topical courseFirst stepComedones and a limited inflammatory burden occur without nodules, rapid scarring or major psychological risk.

1First lineAgree one NICE first-line twelve-week option, commonly fixed adapalene with benzoyl peroxide, after checking pregnancy potential, contraindications and preferences.
2Apply to the whole acne-prone area, introduce alternate-day or short-contact use if irritation is likely, and support with gentle non-comedogenic cleanser, moisturiser and sunscreen.
3Review at twelve weeks for adherence, tolerability, lesion response, pigment change and scars; continue a successful non-antibiotic maintenance option when relapse risk is substantial.

02Moderate to severe acneCombine topical and oral mechanismsNumerous papules or pustules, nodules or substantial truncal disease are present without an isotretinoin emergency.

1Offer a NICE twelve-week combination such as topical adapalene with benzoyl peroxide plus oral lymecycline or doxycycline, or azelaic acid plus one of those oral antibiotics.
2Explain that oral antibiotic therapy must accompany non-antibiotic topical treatment, document pregnancy and age restrictions, and arrange adherence and adverse-effect review.
3At twelve weeks stop the oral antibiotic if clear; if improved but not clear, consider no more than twelve further weeks, and refer after an adequate failed oral-antibiotic-containing course.

03Scarring or high-impact diseaseEscalate before irreversible harmEscalationNodulocystic disease, acne conglobata, new scars, persistent pigment change or severe psychological distress is present.

1Document deep lesions and new structural or pigmentary sequelae, assess mental-health safety and ensure urgent care for acne fulminans or self-harm risk.
2Refer to a consultant dermatologist-led service according to NICE criteria while continuing a safe interim non-conflicting regimen.
3Provide the referral history of completed treatments, duration, adherence, adverse effects, pregnancy potential, mental-health concerns and patient priorities so specialist decisions are not delayed.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

A NICE first-line fixed combination for acne of any severity and a non-antibiotic component of moderate-to-severe treatment.

Adapalene 0.1% with benzoyl peroxide 2.5% gel

Apply a thin film to the entire clean, dry acne-affected area once daily in the evening; reduce to alternate-day or short-contact application initially if irritation occurs.

Avoid in pregnancy or when planning pregnancy, avoid eyes and mucosa, minimise ultraviolet exposure, moisturise for irritation and warn that benzoyl peroxide bleaches hair and fabrics.

An oral tetracycline option combined with a non-antibiotic topical treatment for moderate-to-severe inflammatory acne.

Lymecycline 408 mg capsules

Take one capsule orally once daily as part of a twelve-week acne combination, using the current product information for administration and patient-specific adjustment.

Avoid in pregnancy, breastfeeding and children under 12; review photosensitivity, swallowing, hepatic or renal factors and interacting antacids, iron or calcium, and never combine with isotretinoin.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Permanent scarring

Nodules, delayed effective therapy, recurrent picking and long inflammatory duration increase irreversible atrophic or raised scars, although scarring can occur at any stated severity.

Pigmentary sequelae

Post-inflammatory hyperpigmentation can persist for months or years, particularly in richly pigmented skin, and continued irritation or inflammation prolongs it.

Psychological harm

Visible disease and scars can produce shame, social withdrawal, depression, anxiety, school or work absence and suicidal thinking independent of clinician-rated lesion count.

Acne fulminans

A rare abrupt eruption of painful ulcerating nodules with fever, arthralgia and systemic inflammation needs urgent specialist-led treatment and must not be managed as routine acne.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

At the agreed twelve-week review, compare each lesion type, sites, tenderness, new scars and persistent colour change with the recorded baseline.
Check how often and where each product was used, because spot-only application and irritation-driven interruption can look like pharmacological failure.
Reassess mood, self-esteem, school or work function and self-harm thoughts even when inflammatory lesions are numerically improving.
For oral antibiotics, record the planned stop date and review at twelve weeks; courses beyond six months should be exceptional and reviewed every three months.
Safety-net rapid ulceration, fever, severe pain, new nodules or scars, pregnancy during teratogenic treatment and deterioration in mental health.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Palpation changes the grade

A lesion that looks like flat pigmentation may conceal a tender deep nodule; examine with both sight and touch.

Scarring overrides arithmetic

A modest lesion count with new scars deserves more urgent action than a larger count of superficial stable comedones.

Blackheads are not dirt

Open comedones darken through oxidation, so abrasive cleansing adds irritation without removing the follicular process.

Pigment is an outcome

Persistent post-inflammatory colour change should be documented and discussed rather than dismissed once raised lesions flatten.

Adequate duration matters

Visible improvement takes weeks; a documented twelve-week course distinguishes true failure from premature abandonment.

11Common pitfallsFrequent interpretation and management errors.

01
Grading acne from facial redness alone and missing deep inflammation or truncal nodules in richly pigmented skin.
02
Calling post-inflammatory hyperpigmentation an active comedone and intensifying irritating treatment without examining texture.
03
Delaying referral until scarring is extensive because the absolute inflammatory lesion count seems moderate.
04
Ordering routine hormone or microbiology panels without a clinical pointer to endocrine disease or folliculitis.
05
Treating psychological impact as cosmetic concern rather than a potential determinant of urgency and safety.