How Long Does Poison Ivy Last?

Quick Answer

Poison ivy rash lasts 1–3 weeks in most cases. Mild reactions may resolve in 7–10 days, while moderate to severe cases can take 2–4 weeks to fully clear. The rash itself is not contagious—only the urushiol oil from the plant triggers the allergic reaction.

What Causes Poison Ivy Rash

Poison ivy rash is a form of allergic contact dermatitis caused by urushiol, an oily resin found in the leaves, stems, and roots of poison ivy, poison oak, and poison sumac. About 85% of people are allergic to urushiol. The oil can remain active on clothing, tools, and pet fur for months to years.

Timeline of a Poison Ivy Rash

Stage	Timeframe	What Happens
Exposure	Day 0	Skin contacts urushiol oil
First symptoms	12–72 hours	Red, itchy patches appear (faster if previously sensitized)
Peak reaction	Days 3–7	Blisters form, intense itching, possible swelling and oozing
Blisters dry	Days 7–14	Oozing slows, blisters begin to crust over
Resolution	Days 14–21	Crusts fall off, skin heals; mild discoloration may linger

The rash may appear to "spread" over several days. This happens because areas with thinner skin (wrists, inner arms) react faster than thicker-skinned areas (palms, soles), not because the rash is spreading from one area to another.

Factors That Affect Duration

• Amount of urushiol exposure: More oil contact means a larger, longer-lasting rash
• Sensitivity level: People with higher sensitivity experience more severe, prolonged reactions
• Location on the body: Thin-skinned areas react faster but also heal somewhat faster
• Treatment timing: Washing within 10–15 minutes of exposure can prevent or reduce the rash
• Previous exposures: Sensitivity typically increases with repeated contact

How to Treat Poison Ivy Rash

At Home

• Apply calamine lotion or hydrocortisone cream (1%) to reduce itching
• Take oral antihistamines (diphenhydramine or cetirizine) for itch relief
• Use cool compresses or colloidal oatmeal baths to soothe skin
• Keep blisters clean and avoid scratching to prevent infection
• Wash all clothing, gear, and pets that may carry urushiol

Medical Treatment

• Oral corticosteroids (prednisone) for severe or widespread rashes—typically a 2–3 week tapering course
• Prescription-strength topical steroids for moderate cases
• Antibiotics if blisters become infected

When to See a Doctor

Seek medical attention if:

• The rash covers more than 25% of your body
• Blisters are oozing pus (sign of infection)
• You develop a fever above 100°F (37.8°C)
• The rash affects your face, eyes, or genitals
• Symptoms don’t improve after 7–10 days of home treatment
• You inhaled smoke from burning poison ivy (medical emergency)