Which compound is primarily responsible for the allergic reaction caused by poison ivy?

The compound primarily responsible for the allergic reaction caused by poison ivy is urushiol. Urushiol is a toxic oil found in the leaves, stems, and roots of poison ivy, poison oak, and poison sumac. When skin comes into contact with urushiol, it can trigger an immune response characterized by inflammation and itchiness, leading to the common allergic reaction known as contact dermatitis.

The immune system recognizes urushiol as a foreign substance, which causes T-cells to react and leads to the release of inflammatory mediators that result in the symptoms associated with the allergy.

Understanding urushiol's role in allergic reactions is critical, especially for individuals who may come into contact with these plants, as even minute amounts of the oil can cause severe reactions in sensitive individuals.