Explain why pepper sometimes causes sneezing?

Chemical composition of pepper

Pepper mainly contains a molecule called piperine. It is what gives it its spicy flavor and its distinctive scent. In addition to piperine, pepper contains essential oils, such as limonene and pinene, which contribute to its aroma. These chemical compounds are volatile, meaning they easily evaporate into the air, thus tickling the nostrils when inhaling freshly ground pepper. The fresher the pepper is ground, the more these substances are present in both quantity and intensity, increasing the likelihood of nasal irritation and therefore sneezing.

Reaction of nasal sensory receptors to pepper

In our nose, there are small sensitive sensors called sensory receptors that detect everything that enters our nostrils. When we breathe in pepper, it releases a molecule called piperine, which is particularly irritating. This substance directly binds to these well-known receptors, thereby stimulating the trigeminal nerve present in our nasal cavities. The problem is that this nerve immediately perceives it as an aggression or a threat, quickly sending an alert signal to our brain in the form of a nerve impulse. The immediate result: it stings, it tickles, and the uncontrollable urge to sneeze arises immediately.

Triggering mechanism of sneezing

When the nose detects an irritation, such as pepper, sensitive nerve endings located in the nasal mucosa immediately send a signal to the brain. The sneezing control center, located in a region of the brain called the medulla oblongata, receives this alert message. The result: a chain reaction! A quick and deep inhalation, a reflex closure of the eyes, and then a sudden contraction of the chest and abdominal muscles. All of this rapidly increases the pressure in the lungs. This pressure violently propels air outward through the nose and mouth, thereby expelling irritating particles, such as pepper molecules, and protecting the airways. An express and effective cleaning, but noisy.

Individual factors influencing sensitivity to pepper

Not everyone is equal when it comes to pepper! Some people sneeze easily because they have nasal receptors that are very sensitive to irritating molecules, such as piperine found in pepper. Age also plays a role: generally, as we get older, the nervous system becomes calmer and less responsive to these stimuli. Additionally, your respiratory health is crucial: allergies, rhinitis, or other sensitivities clearly heighten reactions to contact with pepper. People suffering from asthma or having sensitive nasal mucosa often react more quickly and intensely than others. Finally, our habits and regular exposure to spices are also important: someone living in a very spicy culinary culture, accustomed to inhaling pepper, is likely to become less sensitive to it over time.

Comparison with other irritating substances

Pepper is irritating, but frankly, it doesn't have the exclusivity. The onion contains a substance called thiopropanal sulfoxide, which releases an irritating volatile compound when cut, causing not a sneeze but tears. Mustard contains allyl isothiocyanate, capable of tickling our nasal passages, a bit like pepper, triggering frequent tingling and sneezing. The chili pepper, on the other hand, acts differently thanks to capsaicin: this molecule stimulates our pain receptors, giving that typical burning sensation rather than an immediate sneeze. In short, each triggers different reactions, but all are skilled at stirring our senses.