The Greenwich Treehouse sits atop Village Natural restaurant, with a great window vista for people-watching and a curiously high bartop. The staff is friendly, the backroom hosts comedy nights, and the big screen always has the local game dialed up, but it bears mentioning that there is something, either in the air or the beer or the water, that dries out your lips and muddies the mind. Whether it's a spent air filter, brackish ice water, or the pile of birch trees behind the big screen, something in the Treehouse does not sit well with the allergic.