If you've taken a shot of hard liquor, you know how badly it burns on the way down. But how can a room-temperature or even a cool liquid cause this burning sensation? The answer isn't what you might think.
If You Can't Stand the Heat
Your body's normal temperature hovers at, or very close to, 98.6 degrees (37 degrees Celsius). When you drink something cold, that beverage becomes slightly warmer as it travels down your throat and into your stomach. When you drink a hot beverage, the opposite happens: Your body absorbs some of that heat.
And your body can take a lot of heat. For example, coffee drinkers prefer their cup of joe around 140 degrees Fahrenheit (60 degrees Celsius), according to a study published in the Journal of Food Science. So even when you sip on something nearly 30 degrees hotter than your core body temperature, you don't feel like your throat is on fire.
To protect your insides, your mouth and throat both have pain sensors called vanilloid receptor-1, or VR1. VR1 are finely tuned to react to food's temperature and acidity by stimulating neurons to transmit the sensation of pain to the brain. These receptors are super sensitive to both actual high temperatures and perceived heat from compounds like capsaicin, making them react similarly to a sizzling hot slice of pizza as they do to a habanero-laden scoop of salsa.
Fool Me Once
Things change when alcohol comes into play. Ethanol is the type of alcohol found in alcoholic beverages such as tequila. Unlike capsaicin, which makes VR1 think a food is hot to the touch, ethanol binds to these receptors and makes them more sensitive to heat. This bond actually changes the heat threshold, lowering it to just 93.2 degrees Fahrenheit (34 degrees Celsius). This might not seem like a big swing in temperature, but it's enough to cause a flurry of responses in your skin, esophagus, and spinal cord, giving you a sudden sensation of warmth all over and a nasty burn in your throat.
The human body has warning signals in place to protect you from danger. Whether it's a sudden release of adrenaline in life-threatening situations or a pain signal when you eat something that's too hot, reactions in your body are there to tell you not to do something. In the case of downing a shot of liquor, that burning sensation isn't real heat; it's your own body's warning signals gone awry.
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