Why Does Spicy Food Make You Sweat?

You just opened a fresh bag of flaming hot Cheetos and started mindlessly munching on it. After a while, you feel sweat trickling down your forehead even though the room is at your usual 65 degrees. Is it the Hot Cheetos?

The answer is yes. Spicy food can make us sweat even in the coldest of winter. It can also give us a feeling that our tongue is on fire even when the food isn’t actually hot (temperature-wise). All these sensations are the result of a trick played on our brain by a chemical found in chili peppers called… capsaicin.

Table of Contents

Bringing in the heat

If you have a look at sliced chili or hot pepper you will find a white/yellow pulp that holds the seeds together.

Chilli
Credit: Tiia Monto

These pulpy masses contain glands that are home to the active ingredient in hot peppers called capsaicin. It is a colorless, odorless organic molecule with the chemical formula C18H27NO3. Capsaicin belongs to a family of compounds called vanilloids. Even though it belongs to the same family as vanillin, its effects on our body are poles apart from the sweet-smelling, mouth-watering vanilla flavor.

The highly pungent taste of capsaicin is a chemical weapon used by chili plants to shoo away animals from eating its fruits. Like most flora on this planet, chili plants need to protect their seeds for the next generation of plants. Some plants have thorns, some plants are poisonous, and some plants have spicy fruits that create a burning sensation in the mouth, especially for us mammals.

Capsaicin
Molecular structure of capsaicin

As soon as we eat a hot pepper, the capsaicin molecules attach themselves to the mucus membrane in our mouth and start irritating it. The irritation creates the familiar feeling of our mouth and tongue being on fire. It’s the chili plants’ way of telling us, “Stay away from me.” But we humans still can’t stop enjoying our deliciously painful spicy food.

Tricking the brain

Our tongue has thousands of taste buds armed with nerve cells, ready to identify the sweet, salty, sour, bitter, and umami flavors in our food. Identifying tastes is like putting together a puzzle. Taste buds have receptors that are of different shapes and sizes. These receptors can only bind with molecules that can fit perfectly with them, like puzzle pieces.

Types of taste receptors
Types of taste receptors/ 123rf.com

When we chew, the food breaks down and the taste molecules spread all across the mouth, reaching their matching receptors. Once the receptor and food molecules are bound together, they release chemical signals known as neurotransmitters. These neurotransmitters carry the information from the mouth to the brain, which then tells us what we are tasting.

Did you notice that spiciness isn’t on the list of tastes mentioned above? Because it isn’t one; it is a pain response.

The capsaicin molecules don’t get attached to the usual taste receptors. Instead, they bite onto TRPV1, pain receptors that detect temperature and warn us when food is too hot. Once attached to TRPV1, the capsaicin molecules trigger heat-sensing neurotransmitters. This tricks our brain into thinking that the mouth is in contact with something hot like boiling water or a steaming pizza pocket. The sensation like the tongue is on fire is a result of this false alert raised by capsaicin molecules.

Now that our brain thinks we are hot, it has to stop the body from overheating. It does so by starting our body’s in-house air conditioning system: sweat.

We sweat after a long run or when we are out in the sun because that’s how our body regulates its temperature. Sweat droplets absorb the extra heat from the body and use the energy to turn liquid into vapor. This process of removing excess heat is initiated when we eat spicy food, hence the sweats.

Capsaicin tricking the brain
Capsaicin tricking the brain , Credit: Oxford University Press
spicy sweat mechanism
Spicy food sweats mechanism, Credit: Smore Science

A similar reaction is triggered by spicy foods that don’t have capsaicin but have similar spicy molecules, such as piperine found in black pepper or allyl isothiocyanate found in wasabi.

The brain, however, elicits a completely opposite reaction when we eat something minty. The chemical menthol present in spearmint leaves or peppermint extract activates the cold-sensing receptors on our tongue. Hence, the icy cold feeling in our mouths after chewing on some mint gum.

Is there a way to reduce the effect of capsaicin?

You might want to grab a glass of cold water to cool down your tongue, but that could make things worse.

Capsaicin is a hydrophobic substance, which means it doesn’t like to dissolve in water. So, drinking water will just repel the capsaicin molecules and spread them further around your mouth. However, it likes to dissolve in fat, since it is a lipophilic or “fat-loving” molecule. So, our best bet at getting rid of that burning sensation is to eat something with fat content. Cold milk, yogurt, and ice cream are some of the best options out there.

Dairy products contain a lipophilic protein called casein. This protein attracts the capsaicin molecules that are attached to the taste receptors in our mouth. Once the spice molecules are detached from the receptors, casein molecules envelop them and wash them away from our tongues, finally providing some relief.

So, next time you eat spicy food just remember: your mouth isn’t actually on fire. Water will not calm down the heat. Sweating is normal; it’s your body trying to keep you cool.

Capsaicin tricking

Glossary

Allyl isothiocyanate: Also known as AIT, it is an organic sulphur-containing compound with chemical formula CH₂CHCH₂NCS. This molecule gives wasabi, mustard, and horseradish their pungent taste.

Menthol: A naturally occurring volatile organic compound with the chemical formula C10H20O. This compound is responsible for the fresh and cold minty flavor.

Neurotransmitters: These are chemical messengers that carry signals from different parts of the body to the brain.

Piperine: A naturally occurring organic nitrogen-containing compound with the chemical formula C17H19NO3. This alkaloid is responsible for the spiciness of black pepper.

TRPV1: It is a protein in the human body that gets activated by heat and irritants like capsaicin, piperine, and allyl isothiocyanate.

Flesch Kincaid Grade Level: 8.2

Reading Ease: 63.6

References

Why is it that eating spicy, “hot” food causes the same physical reactions as does physical heat (burning and sweating, for instance)? (1999, October 21). Scientific American. https://www.scientificamerican.com/article/why-is-it-that-eating-spi/ Accessed on 7/19/2022

Story, G. M., and Cruz-Orengo, L. (2007). Feel the Burn: The linked sensations of temperature and pain come from a family of membrane proteins that can tell neurons to fire when heated or hot-peppered. American Scientist, 94(4), 326.

Why Chilli Peppers are Spicy: The Chemistry of a Chilli. (2014, January 15). Compound Interest. https://www.compoundchem.com/2014/01/15/why-chilli-peppers-are-spicy-the-chemistry-of-a-chilli/ Accessed on 7/19/2022

Hot Peppers: Muy Caliente. (2013, December). American Chemical Society. https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/archive-2013-2014/peppers.html Accessed on 7/19/2022

Bodily Functions Explained: Spicy Food Reaction (n. d.). Pfizer.Com. https://www.pfizer.com/news/articles/bodily_functions_explained_spicy_food_reaction Accessed on 7/19/2022

 How do our tastebuds work? (2019, September 19). Australian Academy of Science. https://www.science.org.au/curious/people-medicine/how-do-our-tastebuds-work Accessed on 7/19/ 2022

Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.


Join 20,000+ parents and educators
To get the FREE science digest in your inbox!

Author

  • Sanjukta Mondal

    Sanjukta Mondal (she/her) has a Master's degree in Industrial Chemistry and loves to explore the world through the lens of chemistry and her trusty camera. During postgraduate research, she worked on the development of functional materials for battery technology and water treatment. Currently, she is trying to navigate through the labyrinth of scientific writing and science writing, fuelled by coffee and her fascination for the extraordinary science and stories hidden behind everyday objects. Writing for SmoreScience will allow her to explore the enthralling world of science and share it with other curious minds.