It's very frustrating and annoying when you can't really control that you have anxiety. BUT you can learn how to deal with it, which in turn lessens the anxiety and can even dissapear in time. :)
I'd say one thing you could try doing is making yourself do what you want anyway and prove that it's most likely not poisoned.
I do this with my OCD. Or I try to and it's been getting better.
Once before, I noticed that I was beginning to always worry of shutting the door and one of the pets would get stuck in it, so I would check before shutting the door and then check again if anything did happen. I forced myself to stop and now I don't do it anymore.
But sometimes you just can't get past it!
I do agree with everyone else here.
Try to rationalize with yourself too, cognative behavioral therapy.
"Life is an adventure full of beautiful things, and a treasure worth more than gold."