What it is
- An allergic skin reaction to urushiol oil in poison ivy, oak, and sumac. The rash is not contagious, but the oil can spread from plants, pets, tools, or clothing.
How exposure happens
- Touching the plant directly.
- Contact with contaminated objects (leashes, gardening tools, clothing).
- Pet fur can carry the oil to your skin.
Symptoms and timing
- Itchy redness and swelling 12–72 hours after exposure.
- Streaky or linear blisters where the plant brushed the skin.
- New areas can appear over several days—this is from different exposure amounts and skin thickness, not from fluid in blisters.
Immediate first aid (within minutes to hours)
- Wash exposed skin right away with soap and cool running water; scrub under nails.
- Clean contaminated items: clothing (hot wash), shoes, tools (alcohol wipes/soapy water).
- Pet bath with pet shampoo if they brushed plants.
Home treatment
- Itch relief: cool compresses, oatmeal baths, calamine lotion.
- Topical steroids: 1% hydrocortisone for mild areas, early in the rash.
- Antihistamines by mouth (e.g., cetirizine by day; diphenhydramine at night) can help with sleep, though they don’t treat the allergy itself.
- Avoid scratching; keep nails short.
When to seek medical care
- Severe or widespread rash (face, genitals, large body area).
- Swelling around eyes, or eyes are involved.
- Signs of infection (yellow crust, pus, increased pain).
- If over-the-counter care isn’t helping after a few days.
Prescription treatments
- Stronger topical steroids for moderate rashes.
- Oral steroid taper (often 2–3 weeks) for severe or widespread reactions. Important: short bursts (e.g., 5–7 days) can cause rebound—follow the full taper as prescribed.
Prevention and identification
- Learn to recognize local poison ivy/oak/sumac. A common rule: “Leaves of three, let it be” (poison ivy/oak).
- Wear long sleeves, pants, and gloves when hiking/gardening.
- Barrier creams with bentoquatam can reduce penetration if applied before exposure.
- Wash skin within 10–30 minutes of suspected contact; launder clothes and wipe gear.
Myth busters
- Blister fluid does not spread the rash—the oil does.
- Pets don’t get the rash but can carry the oil to you.