Understanding Poison Ivy, Oak, & Sumac - the Basics

What Are Poison Ivy, Poison Oak, and Poison Sumac?

Poison ivy, poison oak, and poison sumac are plants that cause a short-lived but extremely irritating allergic form of contact dermatitis. The rash generally develops within two days after contact, peaks after five days, and starts to decline after about a week or 10 days; people who seem immune at one time and place may find themselves vulnerable in other situations.

What Causes the Rashes?

The leaves, stems, and roots of poison ivy, oak, and sumac plants contain the resin urushiol, and even small amounts on exposed skin can trigger an inflammatory allergic rash.

Urushiol can be transferred by fingers or animal fur and can remain on clothing, shoes, and tools for a number of months. Urushiol particles can also travel in the wind when the plant is burned in a fire. Scratching the rash does not spread the poison to other parts of the body, but it can prolong the discomfort and cause a secondary infection.