shows how gunshot residue was tested for nitrite and lead. When I started shooting, I sorta wondered if I'd react to the GSR, as I've some weird allergies. But thankfully nitrite, lead, etc. are not among them.
Have you thought of wearing a plastic shield, similar to the ones on this site
, as well as nitrile handgloves to prevent/minimize facial and hand skin reactions?
Benadryl is pretty low dosage, OTC anti-allergy medication that will not affect your mind -- only lessen/inhibit your body's reaction to the intrusive allergen.