Writer: Grace Zhang
From Nashville hot chicken to cups of fruit doused with Tajín and chamoy, spicy foods are on fire in modern-day pop culture. Carolina Reaper challenges are all the rage nowadays, and companies are rolling out “World’s Hottest” products like chips, gummy bears, and chocolate bars as if there’s no tomorrow. It’s safe to say that the world loves all things spicy–but scientifically speaking, what is it about peppers that makes them burn? What chemical molecules are in a dash of hot sauce, and how do we perceive the sensation of eating something spicy? What exactly is spice?
It turns out that there is a specific compound responsible for spice. Capsaicin, a vanilloid of the Capsicum family, is a common tissue irritant that evolved in plants as a defensive mechanism against predators and other pathogens [1]. When ingested or put in contact with skin, capsaicin binds to TRPV1, a key receptor located on the outside of cells, activating the mammalian pain pathway [2]. Conventionally, the strength of a given capsaicinoid is measured according to the Scoville Heat Unit Scale, starting from a bell pepper at zero units to pure capsaicin at 16,000,000. For reference, the Da Bomb hot sauce from the show “Hot Ones” clocks in at roughly 135,600 Scoville units [3].
Capsaicin selectively activates certain nociceptors, or specialized neurons that detect pain signals, tricking your nerves into thinking your mouth is on fire in the absence of any real heat [4]. This effect, however, slowly decreases the more spice you eat. Due to its influence on receptors that control pain, researchers have found that regular consumption of spicy foods raises your pain tolerance over time [5]. Eating it once can induce analgesia, or the temporary inability to feel pain. Capsaicin also activates the body's natural painkillers, which are the same opioid receptors that release endorphins, your brain's feel-good chemicals. In short, spice is soothing after a brief flare of pain. That rush of endorphins makes the experience oddly addictive, which might explain why people keep reaching for another bite even when they seem to be in agony.
We’ve discussed how capsaicin can induce a burning sensation by activating pain pathways. So what happens when you realize that the wings you ordered are way hotter than you can handle? The best move is to reach for milk or other dairy products that contain fat and a milk protein called casein. Because capsaicin is an oil-based molecule, drinking milk with a nonzero fat content will help wash it away, similar to how soap removes oil [6]. Furthermore, casein may contribute to breakdown of capsaicin molecules, further relieving spice-induced pain.
Capsaicin can affect your health in many ways. Some studies have linked high spice consumption to higher risks of certain cancers, particularly those of the throat, stomach, and gallbladder. [7]. But other research suggests that capsaicin may actually boost metabolism: people who eat more spicy foods tend to have lower rates of obesity. Additionally, capsaicin could potentially slow metabolic aging processes [8].
Spicy foods have been around for thousands of years, and they’re not going away any time soon [7]. By understanding the biological mechanism of spice, as well as the potential side effects of consuming capsaicin, we are able to make more educated decisions about our individual food choices. As a society, we can conduct research into the science of pain and perception, improving our understanding of how the human body works. So, whether you live for the burn or not, we can all agree on one thing: capsaicin is definitely one way to add a little spice to our lives.
References
[1] Sunil A, Javaheri D. The evolution of capsaicin in chili peppers. Journal of Student Research. 2024;13(3):1–7. doi:https://doi.org/10.47611/jsr.v13i3.2590
[2] O’Neill J, Brock C, Olesen AE, Andresen T, Nilsson M, Dickenson AH. Unravelling the mystery of capsaicin: A tool to understand and treat pain. Pharmacological Reviews. 2012;64(4):939-971. doi:https://doi.org/10.1124/pr.112.006163
[3] Da Bomb Beyond Insanity Hot Sauce, 4oz. HOTSAUCE.COM. Published 2025. Accessed October 18, 2025. https://www.hotsauce.com/Da-Bomb-Beyond-Insanity-Hot-Sauce/?srsltid=AfmBOoqIf8PL9GBy0PFu-6m88P0kmOePKDyKhqaK4QT9ndlDkXdsb59E
[4] Fattori V, Hohmann M, Rossaneis A, Pinho-Ribeiro F, Verri W. Capsaicin: Current understanding of its mechanisms and therapy of pain and other pre-clinical and clinical uses. Molecules. 2016;21(7):844. doi:https://doi.org/10.3390/molecules21070844
[5] Duan G, Wu Z, Duan Z, et al. Effects of spicy stimulation and spicy-food consumption on human pain sensitivity: A healthy volunteer study. The Journal of Pain. 2020;21(7-8):848-857. doi:https://doi.org/10.1016/j.jpain.2019.11.011
[6] McCallum K. How To Cool Your Mouth Down After Eating Spicy Food. www.houstonmethodist.org. Published September 28, 2020. Accessed October 15, 2025. https://www.houstonmethodist.org/blog/articles/2020/sep/how-to-cool-your-mouth-down-after-eating-spicy-food/
[7] Ao Z, Huang Z, Liu H. Spicy Food and Chili Peppers and Multiple Health Outcomes: Umbrella Review. Molecular Nutrition & Food Research. 2022;66(23):2200167. doi:https://doi.org/10.1002/mnfr.202200167
[8] Zhang N, Hong F, Xiang Y, et al. Spicy food consumption and biological aging across multiple organ systems: A longitudinal analysis from the China Multi-Ethnic cohort. Nutrition Journal. 2025;24(1). doi:https://doi.org/10.1186/s12937-025-01147-z