I have no idea if this supplement has any connection to what you're describing. I can tell you, and you can learn this just by Googling it, is that both nattokinase and serrapeptase are suspected of being blood thinners, which can prevent normal clotting. You have to stop taking them if you get surgery, for example. Even bromelain, from pineapple, a very commonly used enzyme used as an antihistamine and anti-inflammatory, is suspected of this. You are speaking of blood vessels, so maybe there's a connection. Unfortunately, doctors are ignorant of virtually everything involving anything pharmaceutical, including and especially naturally derived ones that can't be patented and therefore are frowned upon by the AMA. Also consider that anyone can have a reaction to anything -- we all have odd things we just can't consume. I don't know if anyone knows enough about this to answer the causation question, but if there is, it would have to be a scientific researcher who specializes in enzymes or a specialist who works with them. That wouldn't be your average doc.