Spicy mustard is a versatile condiment that comes in many variations and can be added to virtually any savory dish, sauce, or marinade. Often, the tingling or burning sensation you get in your nose when eating hot mustard is considered part of the experience; however, many find it odd that the spiciness of the condiment is often felt more intensely in the nose than on the tongue. So, why does spicy mustard burn your nose?
Spicy mustard burns your nose because it contains a compound called allyl isothiocyanate. This compound evaporates quickly, and its vapors quickly reach your nasal cavity, irritating the mucous membranes found there, which leads to a burning or tingling sensation.
Due to this process (which I’ll explain in more depth in a moment), the burn you feel from spicy mustard is much more concentrated on your nose than on your tongue. I’ll be explaining the chemical reaction that causes spicy mustard to burn your nose and any related topics in more detail in the following sections, so keep reading to learn more.
The Chemical Reaction That Causes Spicy Mustard To Burn Your Nose
The reason spicy mustard burns your nose boils down to a simple chemical reaction.
When mustard seeds are crushed during the manufacturing process, they release an oily compound called allyl isothiocyanate (or C4N5HS). This is a compound characterized by its ability to evaporate quickly (its vapor pressure is 5 mm Hg at 77.5°F or 25.3°C); therefore, once hot mustard comes in contact with your tongue, the allyl isothiocyanate found within won’t stay in your mouth for long.
Instead, the compound starts evaporating, and its vapors make their way into your nose canal, where it irritates the mucous membranes found there. It comes into contact with nerve receptors, which are essentially a cell’s way of receiving a chemical signal. These receptors then send signals to your brain, allowing you to feel that burning or tingling sensation that you have come to associate with spicy mustard (or mustard of any kind, really).
Certain Receptors Respond to Allyl Isothiocyanate
More precisely, our TRPA1 receptors are the ones that recognize allyl isothiocyanate and send a pain signal to the brain in reaction to it.
The compound in question is found in both mustard and horseradish, which is why the two condiments often cause a similar burning sensation. The main cause that triggers the reaction is the fact that our mucous membranes can be very easily irritated by allyl isothiocyanate; however, even though the physical sensation is supposed to be unpleasant, many humans seem to enjoy it.
You can consider this a failing on our evolutionary responses, as the reason why these compounds trigger this type of reaction in our body in the first place is to ward us off from eating these ingredients in the first place.
The concentration and intensity of the phenomenon are highly affected by the compound’s volatility. Because allyl isothiocyanate evaporates so quickly, most of the burning sensation gets concentrated in your nose instead of your tongue, which is a quality that sets this compound apart from its counterparts that are present in most spicy oils and condiments. However, I’ll dive deeper into this topic in the following sections.
What You Experience When Eating Spicy Mustard
Here’s a quick rundown of what you can expect to experience when eating spicy mustard or any food item containing it in substantial amounts.
First, you’ll get a powerful burning sensation in your buccal cavity. At this point, allyl isothiocyanate hasn’t started evaporating yet, meaning its effects will be felt inside your mouth. The phenomenon occurs when the compound dissolves in saliva and activates the TRPA1 receptors present on the surface of your mouth.
As a result, a signal will be transmitted to your brain, provoking an electrical impulse in the trigeminal nerve. This is the process that allows you to feel the burning or tingling sensation in question.
When the compound evaporates, it starts reaching your nasal cavity and throat, triggering the same chain of reactions all over again. However, this time, the burn you’ll feel will be much more concentrated.
Factors That Can Affect the Intensity of the Burning Sensation
This is a simple overview of the chemical reaction that causes spicy mustard to burn your nose. However, not all types of mustard will have the same effect. The type and intensity of the sensation you get in your nose when consuming hot mustard depend on three factors:
- The kind of mustard seed
- Additional ingredients it has been combined with
- Preparation method
Another factor that can affect the heat level you experience is your unique tolerance to the substance; two people consuming the exact same type and quantity of spicy mustard can always have different reactions to it.
Why Does Hot Mustard Burn Your Nose and Not Your Tongue?
Hot mustard burns your nose and not your tongue because the compound responsible for the burning sensation (allyl isothiocyanate) is highly volatile and doesn’t stay long on the surface of your tongue. Instead, its vapors travel towards your nasal cavity, triggering TRPA1 receptors.
As I already mentioned, these receptors then pass on the signal to the brain, allowing you to feel the burn. However, it’s important to note that the intensity of the sensation you experience is in part due to the high concentration of TRPA1 receptors in your nasal cavity.
Given that there are more TRPA1 receptors in your nose than in your tongue, it’s only natural that the intensity of the burn you feel will differ in the two areas.
Is the Burning Sensation You Get From Spicy Mustard the Same As What You Get From Peppers?
If you’ve read the previous section, you might already have a general idea of what the answer to this question would be. However, for any newcomers, let me reiterate.
The burning sensation you get from spicy mustard is not the same as what you get from peppers. The compounds that cause burning or tingling when you consume hot mustard, wasabi, or horseradish are different from the compounds responsible for these sensations in peppers.
For example, the compound responsible for the nasal flaring caused by spicy mustard is called allyl isothiocyanate, and it is received by our TRPA1 receptors. On the other hand, peppers trigger our TRPV1 receptors through a compound called capsaicin.
TRPA1 receptors are more abundant in our nose cavities, while TRPV1s are more commonly found in our tongues. This further explains why the burning sensations we get from these two different types of ingredients are not usually concentrated in the same area. Moreover, capsaicin is also less volatile than its counterpart, meaning it doesn’t evaporate as easily at human body temperature.
As a result, fewer vapors will reach our throats and nasal cavities, leading to a different type of burning or tingling sensation that’s much more concentrated in the tongue.
Following the same logic, given that most of the allyl isothiocyanate that triggers our response is in vapor form and not tightly bound to receptors (as opposed to capsaicin), its burn also subsides much quicker. This is why even though spicy mustard might cause a stronger initial reaction, the sensation starts dying down relatively quickly, which is more than you can say about the burn that ensues from the consumption of hot peppers.
Conclusion
Spicy mustard burns your nose because of a compound called allyl isothiocyanate. This compound is highly volatile, evaporating quickly and traveling to your nasal canal, where it triggers TRPA1 receptors, which then send a pain signal to the brain. As a result, you feel a burning or tingling sensation.
Sources
- Reddit: ELI5: Why does hot mustard burn in nose and not the mouth like hot chili? : r/explainlikeimfive
- Biology Stack Exchange: What is the biochemical explanation for tingling and burning sensation in brain due to certain food?
- ScienceDirect Topics: Allyl Isothiocyanate – an overview
- PubChem: Allyl isothiocyanate | C4H5NS
- US Pharmacist: Capsaicin: Risks and Benefits
