one thing i was surprised to learn a while back was that you can develop allergies/food intolerances/sensitivities to things that you've been using your whole life, just out of the blue. so even if you'd been eating soy with no problems for years and years, you could still get sick from it suddenly. from what i understand those kinds of allergies/sensitivities spring up when your immune system is feeling overwhelmed, often by unrelated stuff, but sometimes because you've been consuming too much of whatever it is that's made you sick.
it does sound to me, though, like it's a "surface" allergy, meatless. if you've been having other symptoms like runny nose, mood swings, headaches, flushed skin, digestive upset, then i'd think that it had something to do with your diet. i'm not an expert, though! that's just my uneducated opinion. i hope it is just that soap you tried...are you normally sensitive to fragrances, etc?