Fishlegs tells everyone that getting the venom from a slitherwing on their skin will kill them within a day , and clearly Ruffnut and Tuffnut get sprayed by the slitherwing before barf and belch save them and nothing happens to them , but when Astrid gets it on her skin , she starts getting sick almost immediately .
In sandbusted anytime someone said the word tears , tuffnut would break down and start crying , but here he himself says the word tears and it doesn't affect him at all .