Both are possible. I've known of several people who've experienced nausea, myself included. That has generally been from too much rough stuff and/or too soon after eating. Hyperventilation and anoxia can both cause one to pass out, as can dehydration, overheating and sheer exhaustion.
This is why people need to pay attention to more than the ticklish responses. After all, if your lee passes out, the fun is over. Who wants that?! 😉