Type I hypersensitivity is an allergic reaction that is caused by exposure to allergens that triggers an immune response within the body. It generally involves excessive physical reactions visible on the skin or eyes.
Type I hypersensitivity, also referred to as immediate or anaphylactic hypersensitivity, is one of four classes of hypersensitivity. Allergic reactions that result from type I hypersensitivity have many causes, but common triggers are various medications and foods, such as peanut products. Allergic reactions vary in severity and scope and can last anywhere from 15 to 30 minutes, or sometimes longer. Treatment usually involves blocking histamine receptors with antihistamines, although other treatments include the use of adrenaline and corticosteroids.