When urushiol comes into contact with the skin, it triggers a type IV hypersensitivity reaction. This is a delayed allergic reaction mediated by T-cells in the immune system. The reaction typically manifests 24 to 48 hours after exposure, characterized by itching, inflammation, and a rash. In severe cases, it can lead to blistering and oozing lesions. The mechanism involves the body recognizing urushiol as a foreign invader and mounting an immune response against it.
