So, I might be wrong about this, but I think Brandon said at one point that Allomancers might be more resistant to the toxicity of metals. I think he's aware of conundrums like this, and needs some kind of explanation that...makes sense, but kind of has to break a few rules. So, it would just be part of being an Allomancer (in general) gives you the ability to not die (as easily) from ingesting metals.
I think.
Don't quote me on this.
It might all be fake.
Let me spend a few minutes looking for a WoB....
Okay, so...I couldn't find the WoB about what I talked about above, so that's probably completely fake. Random theorizing that doesn't make sense. Here is the WoB that clearly fits your question:
So, the real answer is, "be very careful, and if you mess up, then you only get two hours of sleep that night." Not a very satisfying answer, especially for the Pulsers.