That's why red lipstick makes you think about sex

Keira Knightley once said that dramatic lips are "for when you've had a day and need red lipstick to face the world."

Lies were not found. Because, as the English actress noted, nothing exudes more power and confidence than swiping at a bold shade. But classic makeup does more than just change your attitude. It is also known to be arousing, almost acting like a mating call.

“Red, the color of blood, blush and blush, nipples, lips and genitals filled with sexual arousal, visible from afar and emotionally exciting,” wrote evolutionary psychologist Nancy Atkoff in a particularly impassioned section of her book Survival of the Most Beautiful: The Science of Beauty.

And while that's certainly one way to put it, cosmetics historian Gabriela Hernandez suggested E! News about how its roots are naturally connected to sex.

“This is due to the deep associations in our brain that make this color more attractive in a partner,” she explained. "Red also revitalizes the face, draws attention to itself and will always have a deep connection with sex, since arousal is usually associated with redness."

Another reason why the fiery gaze often makes people cheer up, according to Hernandez, is because it has been "associated with good health" for centuries.

“Red cheeks and lips meant good prospects,” she explained the ancient ideals of courtship. "Good health gave women a better chance of having children and surviving childbirth, which was especially difficult because medicine wasn't developed to help if things went wrong."

Back then, the founder of Bésame Cosmetics explained, the color red meant "youth, which was always more desirable because people didn't live very long."

Ironically, until about the 18th century, many red lip and cheek rouges were made with poisonous ingredients such as cinnabar (derived from red mercuric sulfide), lead, rubric, orschilla weed, red chalk, and alkanet. So while the wearer could put a pinch of red on the lips and cheeks to appear younger, healthier and more beautiful, it would have the opposite effect and ruin them from the inside out.

What's more, in ancient times, you had to carefully balance the line between looking sexy enough to find a mate, but not too sexy to be considered tainted goods.

In ancient Greece, for example, sex workers were required by law to wear red lipstick and obvious face paint to mark their status in society. Otherwise, they will be punished not only for deceiving the public, but also potential spouses, posing as "respectable" women.

And the idea that the most provocative of us prefer red lipstick to other shades continues to permeate our social fabric.

In the late 1930s, according to Rachel Felder's Red Lipstick: An Ode to an Icon of Beauty, the defunct Volupté company sold two lipsticks: Hussey, a bright red, and Lady, a soft pink. By the looks of it, many wore their red with pride, as Hussey outsold Lady by over 80 percent.

And beauty brands today still tend to play up the sex appeal of red. Too Face Cosmetics' raspberry liquid lipstick is called "Nasty Girl," and Rihanna's Fenty Beauty calls its versatile red color "Uncensored."

And it's undeniable that we've associated classic lip color with women who come across as curvy and successful. Marilyn Monroe, Queen Elizabeth I, Cleopatra, Selena Quintanilla, Garden and many more armed with a teasing shade.

One could even argue that red lipstick has become a sex symbol in its own right.

As Rihanna so beautifully put it, “If you have a strong, good lipstick, it changes everything.”