User blog comment:Neowitch/671 - Law's Dating Tips/@comment-4329230-20120613190334/@comment-94.254.85.175-20120613192832

Whenever Luffy gets hit by sleeping gas (or anything that put him into sleep) he goes like this.

http://www.mangareader.net/103-2612-14/one-piece/chapter-505.html

So this is most likely not sleeping gas, its something else...