What is the treatment plan for a patient, likely an outdoor enthusiast, with contact dermatitis probably caused by poison ivy, sumac, or oak?

Treatment Plan for Contact Dermatitis from Poison Ivy, Sumac, or Oak

For contact dermatitis from poison ivy, sumac, or oak, immediately wash the exposed area with soap and water, then treat mild-to-moderate cases with high-potency topical corticosteroids (mometasone furoate 0.1% or betamethasone valerate 0.1% ointment twice daily), and severe cases (>30% body surface area or facial/genital involvement) with systemic prednisone 0.5-1 mg/kg daily for 7 days followed by a 4-6 week taper to prevent rebound dermatitis. 1, 2

Immediate Decontamination (If Presenting Shortly After Exposure)

• Wash the exposed area immediately with soap and water, which removes 100% of urushiol oils if done right away, but effectiveness drops dramatically to 50% at 10 minutes, 25% at 15 minutes, and only 10% at 30 minutes 3, 2
• Even washing up to 2 hours after exposure can reduce symptoms by 55-70% 3, 2
• Remove all contaminated clothing and jewelry before washing 2
• Commercial decontamination products, hand cleaners, or dishwashing soap show similar effectiveness with no significant difference among products 3, 2

Treatment Algorithm by Severity

Mild-to-Moderate Cases (Limited Body Surface Area)

• Apply high-potency topical corticosteroids such as mometasone furoate 0.1% ointment or betamethasone valerate 0.1% ointment twice daily to affected areas 1, 2
• Note that over-the-counter hydrocortisone (0.2-2.5%) has NOT been shown to improve symptoms in randomized trials and should be avoided 3, 1, 2
• Add oral antihistamines for pruritus: use 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 1, 2
• Important caveat: Evidence for antihistamines relieving local itching is uncertain; they primarily help with sleep rather than itch relief 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, Facial/Genital Involvement, or Self-Care Limited)

• 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, 4
• Critical pitfall: The taper MUST be 4-6 weeks long to prevent rebound flare—rapid discontinuation causes rebound dermatitis 1, 4
• Continue high-potency topical corticosteroids to affected areas twice daily 1, 2
• Add oral antihistamines for symptomatic relief 1, 2
• Systemic corticosteroids provide relief within 12-24 hours 4

Supportive Care Measures

• Apply cool compresses to affected areas for symptomatic relief 3, 1, 2
• Consider oatmeal baths for widespread pruritus, though evidence supporting this is limited 3, 1, 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 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 Antibiotic Therapy

• 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, most commonly from Staphylococcus aureus or Streptococcus species

Expected Course

• Contact dermatitis from poison ivy is self-limiting, typically lasting 2-3 weeks without treatment 3, 2
• The extent and severity of symptoms are proportional to the area and duration of exposure 3, 2
• Approximately 50-75% of individuals react to urushiol, the allergic compound in poison ivy 3, 2