Last summer, I was out for a walk to clear my head. The sun was shining and I was lost in thought, so I didn’t take notice when my hand casually brushed up against a plant. I immediately regretted my lack of attention because suddenly, my whole hand began to sting and burn. As the burning subsided, it was replaced by an intense itching as my skin turned red and produced small, raised welts. I had inadvertently run myself right into the leaves of a stinging nettle, a plant that packs a whole lot of histamines and toxins into its leaves and stem.