What is the recommended treatment for a patient with a poison ivy rash?

Treatment of Poison Ivy Dermatitis

For mild to moderate poison ivy dermatitis, apply prescription-strength topical corticosteroids (mometasone furoate 0.1% or betamethasone valerate 0.1% ointment) twice daily, as over-the-counter hydrocortisone has not been shown to improve symptoms in randomized trials. 1, 2

Immediate Post-Exposure Decontamination

• Wash exposed skin with soap and water immediately after contact, which removes 100% of urushiol if done right away, but effectiveness drops rapidly: 50% at 10 minutes, 25% at 15 minutes, and only 10% at 30 minutes 1, 2
• Remove all contaminated clothing, jewelry, and brush off any dry plant material before washing 2
• Commercial decontamination products or dishwashing soap used within 2 hours can reduce symptoms by 55-70%, even when delayed 1, 2

Treatment Algorithm by Severity

Mild Cases (<10% Body Surface Area)

• Apply moderate-to-high potency topical corticosteroids (mometasone furoate 0.1% ointment or betamethasone valerate 0.1% ointment) twice daily to affected areas 1, 2
• Add oral antihistamines for pruritus: loratadine 10 mg daily during daytime, or diphenhydramine 25-50 mg or hydroxyzine 25-50 mg at night for sedative properties 1, 2
• Note that over-the-counter hydrocortisone preparations have NOT demonstrated efficacy in randomized trials and should be avoided 1, 2

Moderate Cases (10-30% Body Surface Area)

• Continue moderate-to-high potency topical corticosteroids twice daily 1
• Add oral antihistamines for symptom control, though evidence suggests they primarily help with sleep rather than directly relieving itch 2
• Consider GABA agonists (pregabalin 25-150 mg daily or gabapentin 900-3600 mg daily) as second-line therapy if antihistamines fail to control pruritus 1

Severe Cases (>30% Body Surface Area or Limiting Self-Care)

• 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 1, 2
• Continue high-potency topical corticosteroids to affected areas 1, 2
• Add oral antihistamines for symptomatic relief 1, 2
• The corticosteroid taper MUST be long enough (4-6 weeks) to prevent rebound flare, which is a common pitfall 1, 2

Supportive Care Measures

• Apply cool compresses for symptomatic relief 2
• Consider oatmeal baths for widespread pruritus, though evidence is limited 2
• Use alcohol-free moisturizing creams or ointments twice daily, preferably with urea-containing (5-10%) moisturizers 1, 2
• Avoid frequent washing with hot water, and avoid skin irritants including over-the-counter anti-acne medications, solvents, or disinfectants 1, 2
• Apply sunscreen SPF 15 to exposed areas every 2 hours when outside 1, 2

Critical Warning Signs Requiring Antibiotics

• Check for secondary bacterial infection: increased warmth, tenderness, purulent drainage, honey-colored crusting, or cellulitis all require antibiotic therapy 1, 2
• These signs indicate superimposed bacterial infection that must be treated separately from the allergic dermatitis 1

Common Pitfalls to Avoid

• Do not use over-the-counter hydrocortisone as it lacks evidence of efficacy; prescription-strength topical corticosteroids are necessary 1, 2
• Do not use short corticosteroid tapers (less than 4-6 weeks) in severe cases, as this leads to rebound flare 1, 2
• Recognize that continued worsening after two weeks may indicate ongoing allergen exposure or development of complications 3
• The rash typically resolves within 1-3 weeks unless there is continued exposure to urushiol 4, 5