The Mood Swing Emotionally Activated Lip Gloss was invented in California. A spokesman for makers Too Faced said: "The colours change depending on your emotional state."
The saucy slap changes from clear to deep crimson as the wearer feels frisky. It works by reacting with a girl's body chemistry.
And each Â£12 tube comes with a colour chart so men can work out how randy their partner is feeling.
Listen ladies, if you really want to let guys know when you're feeling, how should I say -- penis-y, you don't need lip gloss. What you need is....actually, I don't know what you need, I've never been with a girl. THEY SHOULD WEAR SIGNS.
Thanks to Closet Nerd, whose mood ring is always the good color. Green. Or blue. Whichever's better.