Urushiol and allergic contact dermatitis Cross-section of the skin after brushing poison ivy. Urushiol oil left on the surface soaks into the stratum corneum and binds to skin proteins. Immune cells treat the changed proteins as a threat, and the reaction shows up as a red, itchy rash with blisters. SURFACE · FOREARM PHASE 1 · HEALTHY CROSS-SECTION, NOT TO SCALE Urushiol ↓ The oil in poison ivy, oak and sumac.It soaks into the outer skin. Stratum corneum The outer skin. Rash, blisters Red and itchy; can last for weeks. Skin proteins Urushiol binds to them and changes them. Immune response ↑ Immune cells treat the changedproteins as a threat.

Urushiol and allergic contact dermatitis: R&R Lotion, Guide to Poisonous Plants: Understanding, Preventing and Treating Exposure in the Workplace, white paper, Introduction. Illustration for education only.