Acne Severity Classification (IGA Scale)
Grades acne vulgaris with the Investigator's Global Assessment (IGA). NICE NG198 grades severity by lesion count: mild to moderate = up to 34 inflammatory lesions and up to 2 nodules; moderate to severe = 35 or more inflammatory lesions or 3 or more nodules.
Score interpretation
No or very few lesions.
→ Skin care advice (non-alkaline cleanser, avoid oil-based products); maintenance is not always needed — after frequent relapse consider fixed-combination topical adapalene + benzoyl peroxide (NICE NG198). Acne leading to scarring or persistent pigmentary change: consider referral (NICE NG198).
Some non-inflammatory lesions with few papules/pustules and no nodules.
→ 12-week course of a NICE NG198 first-line topical fixed combination (adapalene + benzoyl peroxide, tretinoin + clindamycin, or benzoyl peroxide + clindamycin); skincare advice; review in 12 weeks; no antibiotic monotherapy. Acne leading to scarring or persistent pigmentary change: consider referral (NICE NG198).
Several to many papules/pustules; at most one small nodule.
→ Topical fixed combination; if moderate to severe by NICE count, topical adapalene + benzoyl peroxide with oral lymecycline or doxycycline (or topical azelaic acid with oral lymecycline or doxycycline) for 12 weeks (max 3 months of oral antibiotic); consider combined oral contraceptive in females; dermatology referral if no response. Acne leading to scarring or persistent pigmentary change: consider referral (NICE NG198).
Many inflammatory lesions with nodules (and cysts in very severe acne).
→ Refer nodulo-cystic acne or acne conglobata to a consultant dermatologist-led team; acne fulminans: same-day on-call dermatology (NICE NG198). Specialist isotretinoin — Adults: oral isotretinoin (0.5-1mg/kg/day) — pregnancy prevention programme for females; baseline lipids, LFTs, FBC; monthly monitoring; stop oral antibiotics before starting isotretinoin. Children: use a children's formulary.
Interpretation bands for the Acne Severity. Apply clinical judgement and local guidance.
References
Related
Curated clinical cross-links plus same-class fallbacks.
- Isotretinoin · Systemic retinoid (Vitamin A derivative) / Anti-acne
- Methotrexate (Dermatology — Psoriasis) · Disease-Modifying Antirheumatic / Immunosuppressant
- Doxycycline 100mg (Acne / Rosacea) · Oral tetracycline antibiotic (anti-acne / anti-rosacea)
- Lymecycline 408mg (Acne) · Oral tetracycline antibiotic (anti-acne)
- Erythromycin 2% Topical · Topical macrolide antibiotic (anti-acne)
- Adapalene 0.1% Topical · Topical retinoid (anti-acne)
- Suspicious Pigmented Lesion — Melanoma Pathway · NICE NG14 2015 / BAD
- Cellulitis and Erysipelas · NICE NG141 2019 / CREST
- Psoriasis — Severity Assessment and Step-Up Therapy · NICE NG153 2019 / BAD
- Atopic Eczema — Assessment and Step-Up Therapy · NICE NG95 2023
- Urticaria and Angioedema · BSACI / EAACI Guidelines 2022
- Acne Vulgaris — Grading and Treatment · NICE NG198 2021 / BAD
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.
