If someone has pollen allergies and they are exposed to pollen, what happens to them, physiologically speaking?

?: Physiologically there shouldn't be a problem, but pathologically that would be an allergic (hypersensitivity) disorder with the resultant inflammatory reaction affecting either upper or lower respiratory tracts or both, or the eyes and skin, producing the classic symptoms of asthma, hay fever, atopic dermatitis or conjunctivitis, an allergist would help, check aaaai.org or acaai.org for an allergist