The seeds, like most, would be safe as long as they are not a significant part of their diet (lots of unnecessary calories), same with the plant, might be rather high on tannins or oxolates, given in moderation in a diverse diet shouldn't pose a problem.
I don't think this was the cause of the sneezing, but maybe dust too fine to see, or some actual allergie. Good that you found a solution to that problem.
No matter what you look up on the internet, you will always find people claiming something is unsafe, and that gets repeated over and over by whoever because just to stay on the safe side, and "I have that wisdom from the Internet", reading too much without thinking about the source of the info can leave one pretty paranoid.