Localized Linear Vesiculopapular Rash After Gardening
Most Likely Diagnosis
This is allergic contact dermatitis from poison ivy, oak, or sumac (Toxicodendron species), which characteristically presents as linear vesiculopapular eruptions following outdoor exposure. 1, 2
The linear pattern is pathognomonic—it occurs when plant sap is dragged across the skin during contact, creating the distinctive streak-like appearance that distinguishes this from other dermatoses. 3, 2
Key Diagnostic Features
The linear configuration is the critical diagnostic clue:
- Linear streaks of vesicles and papules are virtually diagnostic of contact dermatitis from brushing against plants during gardening 1, 3
- Toxicodendron (poison ivy/oak/sumac) causes more allergic contact dermatitis than all other contact allergens combined 4
- Eruptions typically appear as erythematous, pruritic vesicles arranged in linear or streak-like patterns 1, 2
Expected timeline:
Critical Differential to Exclude First
Before assuming benign contact dermatitis, you must exclude herpes zoster (shingles), which also presents as linear vesicles:
- Herpes zoster follows a dermatomal distribution with vesicles on an erythematous base, often preceded by 24-72 hours of dermatomal pain 5
- However, zoster is unilateral and does not cross the midline, whereas poison ivy can be bilateral and multifocal 5
- Zoster vesicles coalesce into bullae and typically involve a single dermatome, not scattered linear streaks 5
If there is any suspicion of immunocompromise or if the patient is elderly, consider zoster more seriously, as delayed treatment increases morbidity. 5
Management Algorithm
For Localized, Mild-to-Moderate Cases (Non-Facial):
Topical corticosteroids are first-line therapy:
- Apply triamcinolone acetonide 0.1% cream to affected areas 2-3 times daily, rubbing in gently 6, 1
- Continue for the duration of symptoms, typically 1-3 weeks 3, 4
Adjunctive symptomatic measures:
- Cold compresses for immediate relief 1
- Oral antihistamines (e.g., diphenhydramine) for pruritus control 1
- Cleanse exposed skin within 2 hours of contact to prevent allergen spread 1
For Severe or Extensive Cases:
Systemic corticosteroids are indicated when:
- Eruptions are widespread or involve the face/genitals 1, 3
- Severe bullous lesions develop 7, 2
- Local therapy fails to control symptoms 3
Dosing:
- High-dose oral prednisone (typically 40-60 mg daily, tapered over 2-3 weeks) is necessary for severe cases 7
- A 2-3 week taper is essential—shorter courses risk rebound dermatitis 3, 7
Occlusive Dressing Technique (For Recalcitrant Localized Lesions):
- Apply triamcinolone 0.1% cream, cover with nonporous film, and seal edges 6
- Leave in place for 12 hours (overnight), then remove and reapply cream without occlusion during the day 6
- Discontinue occlusion immediately if secondary infection develops 6
Common Pitfalls to Avoid
Do not use short-course corticosteroids:
Do not dismiss linear vesicles as "just poison ivy" without considering zoster:
- In patients over 60 or immunocompromised, herpes zoster can cause severe complications (postherpetic neuralgia, dissemination) if treatment is delayed 5
- If dermatomal pain preceded the rash or if vesicles are confined to one dermatome, initiate acyclovir empirically 5
Educate patients on plant identification:
- Toxicodendron species are common in gardens, especially if brought from endemic areas (e.g., North America) 7, 2
- "Leaves of three, let it be"—poison ivy has trifoliate leaves with beautiful fall colors, which is why it is sometimes intentionally planted 7, 2
When to Escalate Care
Refer or consult if: