My son (SWCAH) and I (carrier) both get hives every once in a while,  kind of pink, blotchy, itchy ones.  Usually they appear on our neck, back, and inner arms.  They go away very quickly with Benadryl.  It seems that most plants, especially fern-type ones, trigger hives for both of us, even if we don’t come in direct contact with them.  My home is devoid of greenery, save for 2 pothos and 1 aloe plant which all  have to be showered at least once a week.