Yes, it is not a common allergy but it is possible. It has to do with Lipid Transfer Protein Syndrome. I have not been diagnosed officially (long story of a previous visit to an allergist over twenty years ago who declared to me "you cannot be allergic to lettuce it is only water" left me feeling stupid!). Sometimes we have to diagnose ourselves.... now that I don't eat it, the symptoms I once had have disappeared, our bodies tells us when something is amiss!
I envy your spinach and kale meals!