Here's a headcanon for ya! Do you think West get sick?
Honestly, it depends! It all comes down to whether he has Re-Agent in his system or not.
With the introduction of Re-Agent into his system, Herbert can go long periods without sleeping or eating and has accelerated healing accompanied by a fortified immune system and heightened senses. Overall, thanks to the Re-Agent, he's able to scrape by such vicious circumstances, such as the Miskatonic Massacre, with his life intact and a couple of minor scrapes and fractures.
However, after Dan helps ween Herbert off, that's whenever his immune system takes a nose dive. The most common ailments, such as the cold or the flu, hit Herbert like a freight train, leaving him bedridden for days. During these times, he's perhaps the whiniest and clingiest he's ever been; he can't even muster up the energy for a single sly retort to part his lips.
Additionally, during this time, the two end up miraculously bonding.
It doesn't start that way, though—Herbert's overwhelming hubris leads him to refuse Dan's assistance, while Dan grows fed up with Herbert's bullshit. However, as time passes, tensions ease, and the two grow tired of one another. It's during this moment of weariness that Herbert allows tidbits of his past to escape his lips—overall, too weary to keep his skeletons in order.
And what’s Dan’s response, you ask, to his roommate opening himself up like a belly-up frog ready for dissection in a middle school science class? Well, Dan’s there to provide the overdue support Herbert desperately needed…