Acne

Aetiology & Pathophysiology

• Increased androgen sensitivity in the pilosebaceous units leads to:

  • ↑ Sebum production

  • Hyperkeratinisation → keratin plug formation

  • Cutibacterium acnes (C. acnes) overgrowth

  • Inflammation

• Common aggravating factors include hormonal fluctuations (puberty, PCOS), certain medications, and sometimes diet (high glycaemic index foods, though evidence is mixed).

Management

Pharmacological Treatment Ladder

Severity Classification

• Mild: Comedones and papulopustules, mainly in the T-zone (forehead, nose, chin)

• Moderate: Features of mild acne plus nodules on the face ± trunk involvement

• Severe: Features of moderate acne plus cysts, scarring, or extensive involvement of the face and trunk

Stepwise Treatment Approach

1. Start with OTC benzoyl peroxide (BP) 5%

   • Often used as first-line for mild acne; available in creams, washes, gels.

   • Warn patients about possible dryness, bleaching of clothes/towels, and mild irritation.

2. Topical Therapy

   • Comedonal (minimal inflammation): Topical retinoid (e.g. adapalene 0.1%)

   • Comedonal + inflammatory: Combination benzoyl peroxide 2.5% + adapalene 0.1%

   • Inflammatory predominant: Combination benzoyl peroxide 5% + topical clindamycin 1%

   • Therapy must be continued for at least 6 weeks to assess response.

3. Oral Therapy (if inadequate response to topical agents or if moderate/severe)

   • Oral antibiotics (e.g. doxycycline 100 mg daily or erythromycin 400 mg BD) for 6–12 weeks

     • Doxycycline is generally first-line unless contraindicated or not tolerated.

     • Combine with topical retinoid and/or benzoyl peroxide to reduce antibiotic resistance.

   • Hormonal therapy in females (e.g. combined oral contraceptive pill [COCP], especially an anti-androgenic formulation such as ethinyloestradiol + cyproterone acetate, or spironolactone 50–100 mg daily if androgenic symptoms or PCOS is present).

   • If ineffective, consider dose escalation or changing the oral antibiotic class (e.g. from doxycycline to erythromycin).

4. Severe or Resistant Acne

   • Oral isotretinoin is often considered last-line in primary care, particularly for cystic or scarring acne.

   • Referral to a dermatologist may be warranted for isotretinoin initiation if the GP is not experienced in prescribing, or if there are complex comorbidities.

Mechanism of Retinoids

• Reduces keratinisation: Helps unblock pores and prevents microcomedone formation.

• Reduces inflammation: Suppresses inflammatory pathways in the skin.

• Most effective for comedonal acne: Often used long-term for maintenance once inflammatory lesions are controlled.

Side Effects of Oral Isotretinoin

• Initial acne flare in the first few weeks

• Mucocutaneous dryness: Dry lips (cheilitis), dry skin, dry eyes

• Teratogenicity: Absolute contraindication in pregnancy; requires reliable contraception (two forms recommended)

• Photosensitivity: Advise use of broad-spectrum sunscreen

• Mood changes (depression, anxiety) – monitor mental health

• Rare but serious:

  • Benign intracranial hypertension (risk is higher if combined with tetracyclines, so avoid doxycycline)

  • Agranulocytosis (very rare)

  • Skin fragility, hair thinning, epistaxis

When to Refer to a Specialist

• Failure or intolerance of standard therapies (topical ± oral antibiotics ± hormonal therapy)

• Severe acne (cystic, nodular, scarring)

• Significant psychosocial impact (anxiety, depression, self-esteem issues)

• Scarring or strong family history of severe scarring

• Consider referral for oral isotretinoin if the GP is not comfortable prescribing or monitoring

Non-Pharmacological Management

• Address underlying factors such as PCOS or other endocrine disorders if suspected.

• Use non-comedogenic skin products (cosmetics, moisturisers, sunscreen).

• Avoid picking or squeezing lesions to prevent scarring.

• Regular cleansing with soap-free or gentle cleansers (avoid over-washing, which can irritate skin).

• Identify possible triggers like high-humidity environments, some dietary factors.

• Avoid known acnegenic medications where possible (e.g. certain progestin-only contraceptives, corticosteroids, anabolic steroids).

Additional Notes

• Topical retinoids and spironolactone are contraindicated in pregnancy (Category D).

• Topical and oral antibiotics can take approximately 6 weeks to show visible improvement.

• COCP often requires up to 6 months to achieve maximum benefit in acne.

• Oral isotretinoin:

  • Avoid using doxycycline concurrently (risk of benign intracranial hypertension).

  • If antibiotic coverage is needed, erythromycin 400 mg BD is a safer option.

  • Baseline blood tests (lipids, LFTs) and repeat monitoring may be required depending on local protocols.

• Doxycycline is contraindicated in idiopathic intracranial hypertension (IIH) and in children <8 years old (dental staining).

• Retinoids are preferably used at night, and broad-spectrum sunscreen should be used in the morning (non-comedogenic products like Cetaphil or La Roche-Posay Anthelios).

Differential Diagnosis

Infantile Acne

• Onset typically at 3–4 months of age, resolves by ~1 year.

• Unknown aetiology; may be more inflammatory or comedonal.

• Mild: Benzoyl peroxide 5% (inflammatory) or adapalene 0.1% (comedonal).

• Mixed inflammatory + comedones: Combination benzoyl peroxide 5% + adapalene 0.1%.

• If refractory, consider referral for oral erythromycin or isotretinoin.

• No tetracyclines in children <8 years (risk of dental staining).

Neonatal Cephalic Pustulosis

• Usually due to Malassezia overgrowth; not true acne as there are no comedones.

• Onset ~4 weeks old.

• Treatment usually self-limiting; can use ketoconazole 2% cream BD for 2–3 days if needed.

Other Neonatal Conditions

• Toxic erythema of the newborn: Red blotches, often resolves in 1–2 days, sparing palms and soles.

• Milia: Pearly white cysts, benign, no treatment required.

• Miliaria: Blocked sweat ducts, improves with cooling measures.