Why Sichuan Peppers Make Your Mouth Buzz, According to Science

When you eat or drink something, your mouth can experience any of these five tastes: sweet, salty, sour, bitter, and savory (also known as “umami”). But what about the mouth-numbing tingle you get from that bowl of sichuan pepper-laced mapo tofu? What exactly is that?

If you’ve never experienced the peppers, Yao Zhao, founder of 50Hertz Tingly Foods, which features the peppers in their products, paints a pretty vivid picture. “At first, you smell the floral aroma, then quickly you feel a tingling sensation like licking the terminals of a nine-volt battery, or eating Pop Rocks, or drinking sparkling water,” he says. But in a good way.

Okay, But Why So Tingly?

In a study released in 2013, researchers from the Institute of Cognitive Neuroscience at University College London studied that sensation. The study found that the perceived frequency of tingling generated by Sichuan peppers was equal to 50 hertz, or the feeling of 50 vibrations per second.

“It doesn’t hurt, nor is it painful or irritating like capsaicin. It lingers for a few minutes and goes away. It’s fun and energizing!” Zhao says. “We describe it as an ‘edible sensory experience’ that’s like nothing else you’ve ever experienced.”

What Causes the Tingling? Turns Out, It’s All In Your Head

Eating Sichuan peppercorns stimulates your trigeminal nerve. That’s part of the nervous system located in the head, which is responsible for sensations in the face and mouth, including pain, touch, and temperature. But not taste.

 And Sichuan peppers aren’t the only foods playing mind games. “The burn that you get from capsaicin, the source of chili peppers’ spiciness, the impact of the cooling sensation of menthol and the effervescence of carbonation are all due to trigeminal stimulation,” says sensory and consumer scientist Lori Rothman, member of the Sensory and Consumer Sciences Division at the Institute of Food Technologists (IFT).

To dive a little deeper, Sichuan peppercorns have a compound named hydroxy-alpha sanshool which creates the tingling, effervescent, and mouthwatering effect. Other trigeminal compounds can lead to other effects like numbing, cooling, or even burning in your eyes when you cut onions.

“Importantly, trigeminal irritants are also known for causing endorphin releases during consumption, which is a true high experience,” says Michael Nestrud, PhD, vice president of strategic accounts at Curion Insights and member of the Sensory and Consumer Sciences Division at the IFT. (Scientists use the term “irritant” to describe these compounds because for them, an irritant is anything that can stimulate a nerve [positively or negatively]. But, it’s not necessarily ‘irritating’ the way we might think of the word in every-day use.)

“All those extreme spicy food eaters partially do this because they like to, but partially because they like the head change that occurs with endorphin releases. This is a reminder that we aren't 100% in control of our own preferences!”

So, What Is Sichuan Pepper?

Sichuan peppercorns or peppers are widely used in Sichuan and other Chinese cuisines. However, they’re not actually a pepper, but a citrus fruit that is harvested from the prickly ash tree.

“Dried [Sichuan] peppers look like flower petals or little Pac-man,” says Zhao. “There is no heat (capsaicin) when you try Sichuan pepper. Instead, you will taste and smell its intense floral aroma and feel the unmistakable tingling sensation on your tongue.”

Sichuan peppers are grown, then handpicked in the western part of China where they thrive on mountainous terrain. As they’re laid to dry in the sun, the berries open and release their black seeds.

The peppers come in red and green varieties. Red Sichuan peppers have been used for centuries for cooking, but green peppers are less common and have only become popular in China the past two decades, Zhao says.

He compares green peppers to white wine, describing them as “brighter, more aromatic, and citrusy” while red peppers are more full-bodied and woodsier, like red wine.

Zhao says he grew up eating Sichuan peppers, but didn’t appreciate the tingling sensation for years. “It was only after I traveled and lived all over the world, that I realized that this is a unique spice that you can not only taste, but also feel,” he says. “So, that's why I’ve become the Sichuan pepper guy and it’s my goal to make my hometown spice known to the rest of the world.”