What is the name of the movie? A spider crawls into a horses nose and then the horse starts sneezing spider webs and goes nuts and envelops a child in his nose web.
I think you are looking for this scene
from "The Brothers Grimm."
The spider does indeed crawl up the horse's nose, and when the child goes to investigate the commotion the horse is making, she is caught in a spider web coming from the horse's mouth and swallowed.