How many sensitivities to a particular antigen be determined?

/in /by

After working in a mushroom farm for several months, a worker develops these hives, edema, and swelling lymph node
a) What do these symptoms indicate?
b) What mediators cause these symptoms?
c) How many sensitivities to a particular antigen be determined?
d) Other employees do not appear to have any immunological reactions. What could explain this?
(Hint: The allergen is conidiophores from molds growing in the mushroom farm)