Confusable diagnoses · PANCE / PANRE

Acne Vulgaris vs Rosacea

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Acne Vulgaris and Rosacea are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Acne Vulgaris vs Rosacea at a glance

  • Acne Vulgaris: Chronic inflammatory disorder of the pilosebaceous unit driven by androgens, sebum, keratinization, and Cutibacterium acnes.
  • Rosacea: Chronic centrofacial inflammatory dermatosis with flushing, persistent erythema, telangiectasias, papules/pustules, and ocular involvement.

Try two board-style questions on Acne Vulgaris vs Rosacea

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Question 1DermatologyMedium
A 22-year-old man with moderate acne (comedones, inflammatory papules, pustules on face, chest, back) has failed 2 months of benzoyl peroxide alone. Which of the following is the most appropriate next step in therapy?
  • AIntralesional triamcinolone
  • BTopical retinoid plus antibiotic
  • COral azithromycin pulse therapy
  • DOral isotretinoin
Reveal answer & full explanation
Correct answer: B — Topical retinoid plus antibiotic
  • AIntralesional triamcinolone
  • BTopical retinoid plus antibiotic✓
  • COral azithromycin pulse therapy
  • DOral isotretinoin

Why Topical retinoid plus antibiotic is correct

  • Acne is treated stepwise: mild acne (comedones only) = topical retinoid monotherapy; moderate acne (comedones plus inflammatory papules/pustules) = topical retinoid plus a topical benzoyl peroxide (BPO)-antibiotic combination
  • Benzoyl peroxide must be included in any regimen using topical antibiotics to prevent Cutibacterium acnes resistance
  • Tretinoin should be applied at night with sunscreen used during the day; adapalene 0.1% gel is available over the counter

Why the others are wrong

  • Intralesional triamcinolone — used for individual nodulocystic lesions, not widespread moderate acne (right-concept-wrong-scope)
  • Oral azithromycin pulse therapy — macrolides are reserved for patients who cannot take a tetracycline (pregnancy, children younger than 8), and oral antibiotics should never be used as monotherapy; when a systemic agent is added for moderate acne, doxycycline or minocycline is preferred, combined with a topical retinoid and BPO (wrong-drug-class)
  • Oral isotretinoin — reserved for severe/nodulocystic or refractory disease, not this stage (premature escalation)

Additional high-yield points

  • Oral antibiotics (doxycycline 100 mg or minocycline 50-100 mg BID) are used for moderate-to-severe acne; keep the course as short as possible and reassess at 3-4 months
  • Females with hormonal acne: oral contraceptive pills and/or spironolactone are options
Question 2DermatologyMedium
A 44-year-old woman of northern European descent presents with an 8-month history of facial redness. She reports episodic flushing triggered by hot beverages, red wine, and emotional stress, along with persistent burning and stinging when she applies moisturizer. On examination she has fixed erythema and telangiectasias across the cheeks, nose, and central forehead, with scattered dome-shaped papules and pustules and no comedones; the periocular and perioral skin is spared. Which of the following best explains the findings?
  • AAndrogen-driven follicular hyperkeratinization with Cutibacterium acnes overgrowth
  • BOveractivation of innate immunity with excess cathelicidin LL-37 and kallikrein-5
  • CIgE-mediated mast cell degranulation in a type I hypersensitivity reaction to food
  • DType IV delayed hypersensitivity reaction to a chronic topical contact allergen
Reveal answer & full explanation
Correct answer: B — Overactivation of innate immunity with excess cathelicidin LL-37 and kallikrein-5
  • AAndrogen-driven follicular hyperkeratinization with Cutibacterium acnes overgrowth
  • BOveractivation of innate immunity with excess cathelicidin LL-37 and kallikrein-5✓
  • CIgE-mediated mast cell degranulation in a type I hypersensitivity reaction to food
  • DType IV delayed hypersensitivity reaction to a chronic topical contact allergen

Why Overactivation of innate immunity with excess cathelicidin LL-37 and kallikrein-5 is correct

  • Rosacea is driven by dysregulated innate immunity: kallikrein-5 (a serine protease) abnormally cleaves the antimicrobial peptide cathelicidin into proinflammatory LL-37 fragments, which promote vascular ectasia, leukocyte recruitment, and angiogenesis.
  • This pathway, combined with neurovascular dysfunction (TRPV1/TRPA1 sensitization causing trigger-induced flushing), Demodex-driven inflammation, and an impaired skin barrier, produces the centrofacial erythema, telangiectasias, and papulopustules seen here.
  • The phenotype is classic: persistent centrofacial erythema, telangiectasia, and papules/pustules WITHOUT comedones, sparing the periocular and perioral skin.

Why the others are wrong

  • Androgen-driven follicular hyperkeratinization with Cutibacterium acnes overgrowth is the mechanism of acne vulgaris; the absence of comedones and the fixed flushing/telangiectasias point to rosacea, not acne.
  • Type IV delayed hypersensitivity to a topical contact allergen produces eczematous, pruritic, often vesicular plaques in the distribution of the allergen, not fixed centrofacial erythema with telangiectasias and trigger-induced flushing.
  • IgE-mediated mast cell degranulation in a type I hypersensitivity reaction underlies urticaria and angioedema with transient wheals; it does not explain the persistent erythema, telangiectasias, and papulopustular changes of rosacea.
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Side-by-side comparison

FeatureAcne VulgarisRosacea
At a glanceChronic inflammatory disorder of the pilosebaceous unit driven by androgens, sebum, keratinization, and Cutibacterium acnes.Chronic centrofacial inflammatory dermatosis with flushing, persistent erythema, telangiectasias, papules/pustules, and ocular involvement.
Classic presentationMixed comedonal and inflammatory lesions in seborrheic distribution (forehead, nose, cheeks, chin, upper chest and back).; Visible facial, chest, or back lesions; mild tenderness with inflammatory papules and nodules; Psychosocial distress, anxiety, depression — disproportionate to objective severity in many patients; Post-inflammatory…Centrofacial distribution sparing periocular and perioral skin; absence of comedones distinguishes from acne.; Episodic flushing in response to triggers, lasting minutes; Persistent centrofacial erythema (cheeks, nose, chin, central forehead) — spares periocular skin; Burning, stinging, dryness, sensitivity to topicals; Ocular: foreign…
Workup / key labsClinical diagnosis based on lesion morphology and distribution. Severity graded as mild (comedonal ± few inflammatory papules), moderate (numerous papules/pustules ± few nodules), or severe (widespread nodulocystic disease, scarring, or failure of prior therapy).; Generally clinical diagnosis — no routine labs; If suspect…ROSCO 2017 phenotype-based criteria. Diagnostic: persistent centrofacial erythema OR phymatous changes. Major: flushing, telangiectasia, papules/pustules, ocular findings (lid margin telangiectasia, conjunctival injection, keratitis).; Clinical diagnosis — no laboratory testing required; Consider ANA if photosensitive malar rash or…
ImagingNot indicated for routine acne; Pelvic ultrasound if PCOS suspectedNot indicated
First-line treatmentMild comedonal: topical retinoid — tretinoin 0.025-0.1%, adapalene 0.1-0.3%, tazarotene 0.05-0.1% (apply at night; avoid all topical retinoids in pregnancy — tazarotene is contraindicated; start every other night to limit irritation); Mild-moderate inflammatory: benzoyl peroxide 2.5-10% ± topical antibiotic — clindamycin 1%,…General: trigger avoidance, daily broad-spectrum sunscreen SPF ≥30, gentle non-soap cleansers, fragrance-free moisturizer; Persistent erythema: topical alpha-agonists — brimonidine 0.33% gel daily or oxymetazoline 1% cream daily (rebound erythema possible); Telangiectasias: pulsed dye laser, KTP laser, or intense pulsed light (IPL);…

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Full outlines

Acne Vulgaris Rosacea All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.