is poison ivy a type iv immune reaction?
Allergic inflammations, also called hypersensitivities, are caused by three underlying mechanisms. The one which is responsible for the reaction to poison ivy is called delayed hypersensitivity. Delayed hypersensitivity does not start to be noticeable until several hours to a full day after exposure to the antigen.
As is the case with all contact dermatitis, urushiol-induced rashes are a Type IV hypersensitivity reaction, also known as delayed-type hypersensitivity. Symptoms include itching, inflammation, oozing, and, in severe cases, a burning sensation.