Kids with nut allergies,has yours ever gotten a reaction from..?

foods that list "this product was processed in a plant that also handles...." or "manufactured on shared equipment that also processes..."? My daughter has a nut allergy and I avoid these products when I am aware of the processing. I'm sure she's had stuff like this (w/o incident) for instance,certain cake mixes are made in plants that handle pecans (daughter is severely allergic). I was wondering if the lables are for extra precaution or if reactions actually occur. And YES,I avoid them at all costs.