Ever notice how your lips sometimes tingle after eating certain spicy foods? That's because spices can be skin irritants -- aka "lip plumpers."
Products that claim to make your lips bigger may in fact do just that (for about an hour or two), but this is not high science we're talking about. Most lip plumpers use ingredients like cayenne, cinnamon and ginger, along with other zingy additives like menthol and wintergreen, to irritate lips into swelling.
A few products use ingredients that dilate blood vessels, such as niacin or retinol, to achieve a plumping effect, but those are an even-more-expensive minority.
In most products, other than irritation it's about reflecting light. And you can do that with your plain-old lip gloss. Mix a tiny bit of red pepper or cinnamon in that gloss and voila -- plumper lips.
Next: Very few people are that lazy.