Science! That is what explains how Mood Swing Emotionally Activated Lip Gloss works, I assume. The makers claim that when a lady wearing it is in the mood for carnal pleasures, it turns deep red.
How does it work, you ask? By "reacting with a girl's body chemistry." Oh, I see, well that sure explains it.
And even if it does work, I'm not sure what the benefit is. I mean, do you ladies out there really want to show your cards that obviously? Whatever happened to the mystery? [The Sun via The Daily What]
DISCUSSION
There are already ways to tell. The easiest (except for utterly clueless guys) include: She will tell you so; She will be wearing FMPs; She will have "things" in her purse that would anable her to sleep not at home that evening (tooth brush, etc).
Or just wait till the moon is full.