For some lip plumpers, the tingly comes from stuff like cinnamon and ginger, natural irritants that make sensitive lips swell. I think that's what DuWop does, and they were the first.

Yep, here's what their site says:

"The secret behind Lip Venom is a blend of essential oils, which include cinnamon, wintergreen, and ginger, that cause the blood to rush to the surface of the lips, flushing and swelling them slightly. The gloss also includes jojoba and avocado oil that moisturize and give the lips intense shine."

So, not all chemmy :-) Ouchie if you're sensitive, though! (I have to check on the ingredients in the Soap &amp; Glory version, but Sexy MotherPucker... OWW.)