I did note that when House cut the onion that HIS eyes didn't tear up.
He kept turning his head away, widening his eyes, then dobbed them with a handkerchief afterwards, so I'm pretty sure his eyes did tear up. Of course, that was before he ordered the "artificial tears to maximize the visual impact of this moment."
"It's not so much that it's 'shut down' as the government has been rebooted into safe mode."
- Tim and Daniel Shamblin