Hives from Sunscreen?

I put some sunscreen on my daughter (Alba Botanica-mineral sunblock) with organic ingredients, no chemicals. However the last ingredient is sodium benzoate, a preservative. The next morning she has what appears to be hives, red bumps, itchy, splotchy and slightly swollen on  her face and arms, exactly where I put the sunscreen. I think it is from the sodium benzoate, I know when she has eaten foods with this preservative she got red splotches around her mouth, also when she was a toddler from raw cinnamon, which contains benzoic acid naturally, I think this is all related. Has anyone ever heard of this kind of reaction?  I am very careful about buying prodcuts without chemicals and toxins, but it is so tricky when reading labels. I felt deceived after reading the ingredients, just by looking at the front of the tube and reading, mineral, organic, hypo-allergenic, paraben free and then my child gets hives!!