Think about the last time you ate something spicy, whether it be Hot Cheetos, a jalapeño, or sriracha. Did your nose flush? Did you sweat? Cry? And what did it feel like? Like you were breathing fire or like you were getting your tongue pinched?
Those are sensations many of us have experienced to some degree when we’ve eaten spicy foods. The question is: why? Just as we know what it feels like to eat something spicy, we also know that eating a bowl of cereal does not feel that way – at all (at least I hope your cereal isn’t spicy). So, what’s the difference between the bowl of cereal and the sriracha?
To answer the million-dollar question - why? - it is imperative to start from the basics: the sense of taste. Knowing what “taste” is and how we experience it tells us why spice is experienced differently than sweet or sour.
Our sense of taste
While it may feel like there are millions of tastes, there are actually only five basic tastes: salty, sweet, sour, bitter and umami (described as brothy/meaty). These basic tastes combined with the sense of smell are what produces our perception of different flavors and allows us to differentiate an apple from a potato.
To allow for the experience of these five basic tastes, we have little bumps called papillae all over our tongue, and inside each of these bumps are several taste buds. Each taste bud contains 50-100 taste receptor cells that are activated by proteins, molecules, and charged particles called ions that are present in our food. Activation by ions produce salty and sour tastes, while activation by different proteins and molecules produce sweet, bitter and umami.
A common myth is that certain regions of the tongue perceive only a certain taste (sweet at the tip, bitter at the back, etc.). This is not true; taste buds (found all over the tongue) contain receptors for all tastes!
Once activated, the receptor cells send an electrical signal that reaches the brain, allowing for the translation of chemicals in our food into a taste.
Spice is not a taste
Notice that “spicy” is not on the list of basic tastes detected by the tongue. So, then, what is spice? As I mentioned, foods contain particular chemicals – called tastants – that stimulate sensations detected by the tongue. The sensation that accompanies spice does not come from tastants, but rather from other chemicals called capsaicinoids. These chemicals trigger heat and pain receptors in the tongue. Hence, when you eat spicy food, you feel as if your tongue is burning and being pinched; the receptors in your tongue are actually telling your brain that it is burning! In response, your body reacts by sweating and flushing – the natural responses to increase in warmth. So what we perceive to be the “taste” of spice is actually a physiological response to pain and heat stimulation.
Why do we like spice?
After all this, one question remains: if it is painful, why do we eat spicy food?
Without diverting too far into the nitty-gritty neuroscience of it all, the simple answer is this: in response to the pain, the brain releases hormones that cause relief and stimulate pleasure. Ultimately, the pleasure stimulated by spiciness, as it simulates pain, is what encourages us to love spicy food (if we can manage to tough it out until the end)!
 Tirado-Lee, Leidamarie. “This is your brain on capsaicin.” Helix magazine. July 2014.