Poison Ivy Onset and Treatment
Typical Onset Timeline
Poison ivy dermatitis typically begins within days of exposure and lasts up to 3 weeks, with symptoms including redness, papules, vesicles, and itching that are proportional to the area and duration of contact. 1
- The characteristic streak-or-line-like appearance of the rash usually clears within 1-3 weeks unless there is continued allergen exposure 2
- Approximately 50-75% of individuals react to urushiol, the allergic compound in poison ivy 1
Immediate Post-Exposure Decontamination (Time-Critical)
Washing with soap and water immediately after contact removes 100% of poison ivy oils, but effectiveness drops dramatically: 50% at 10 minutes, 25% at 15 minutes, and only 10% at 30 minutes. 1, 3
- Remove contaminated clothing, jewelry, and brush off dry plant material before washing 3
- Commercial decontamination products, hand cleaners, or dishwashing soap produce 55-70% symptom reduction even when used up to 2 hours after exposure, with no significant difference among products 1, 4
- A study comparing Tecnu (70% protection), Goop (61.8%), and Dial soap (56.4%) found all three significantly better than no treatment, with differences between products being statistically nonsignificant 4
Treatment Algorithm by Severity
Mild to Moderate Cases
For mild to moderate dermatitis, apply moderate-to-high potency topical corticosteroids (mometasone furoate 0.1% ointment or betamethasone valerate 0.1% ointment) twice daily to affected areas. 5
- Over-the-counter hydrocortisone (0.2%, 1.0%, 2.5% formulations) has NOT been shown to improve symptoms in randomized trials 1, 5, 6
- Only prescription-strength topical corticosteroids combined with systemic steroids have demonstrated efficacy in reducing itch duration 5
- Add oral antihistamines: non-sedating second-generation antihistamines (loratadine 10 mg daily) during daytime, or first-generation antihistamines (diphenhydramine 25-50 mg or hydroxyzine 25-50 mg) at night for sedation 5
Important caveat: Evidence for oral antihistamines relieving local itching is uncertain; they may primarily help with sleep rather than itch relief 1, 5
Severe Cases or >30% Body Surface Area Involvement
Initiate systemic corticosteroids immediately with prednisone 0.5-1 mg/kg body weight for 7 days, followed by a weaning dose over 4-6 weeks. 5
- Continue high-potency topical corticosteroids to affected areas 5
- Add oral antihistamines for symptomatic relief 5
- Critical pitfall: Ensure the corticosteroid taper is long enough (4-6 weeks) to prevent rebound flare 5
Second-Line Therapy for Refractory Pruritus
- Consider GABA agonists (pregabalin 25-150 mg daily or gabapentin 900-3600 mg daily) if antihistamines fail to control itching 5
Supportive Care Measures
Apply cool compresses and consider oatmeal baths for symptomatic relief, though evidence supporting these interventions is limited. 1, 3, 5
- Use alcohol-free moisturizing creams or ointments twice daily, preferably with urea-containing (5-10%) moisturizers 5
- Avoid frequent washing with hot water and skin irritants including over-the-counter anti-acne medications, solvents, or disinfectants 5
- Apply sunscreen SPF 15 to exposed areas every 2 hours when outside 5
Critical Warning Signs Requiring Antibiotic Therapy
Check for secondary bacterial infection: increased warmth, tenderness, purulent drainage, honey-colored crusting, or cellulitis all require antibiotic therapy. 5