Pollen can generate an immune response which is known as hypersensitivity. Hypersensitivity is an uncontrolled and unregulated immune response. Pollen generates IgE mediated type I hypersensitivity which causes acute inflammation in the body which ultimately result in wheals and flares on the skin. It causes hyper activation of mast cells and basophils which cause vasodilation by releasing molecules like leukotrienes, serotonin and prostaglandins. Asthama and atropic dermatitis are the two diseases which occur due to pollen allergies.
I'd say C. an allergic reaction. Mainly because lots of people are allergic to many things and many people intend to have seasonal allergies cause by plants. Hope it helps!
