There are four different types of hypersensitivity reactions. Some evidence suggests a potential fifth type, but this may actually be a subset of type 2 hypersensitivity reactions.

Penn State researchers have uncovered a surprising twist in a foundational chemical reaction known as oxidative addition.

There are four different types of hypersensitivity reactions. We discuss the RA hypersensitivity type, what causes it, and how this type of reaction is diagnosed and treated. Learn more about RA.