The sudden onset of a sneeze immediately after inhaling from a cartridge is a common physiological reaction that signals irritation in the nasal passages. This response is not a malfunction but a protective mechanism the body uses to expel perceived threats from the airway. The reaction is triggered by a combination of specific chemical compounds within the vapor and the physical manner in which the vapor is inhaled. This article will explore the biological, chemical, and behavioral factors that contribute to this reflex.
The Sneeze Reflex and Nasal Irritation
The sneeze, or sternutation, is a coordinated, protective respiratory reflex initiated by the stimulation of sensory nerve endings within the nasal lining. This reflex is mediated by the trigeminal nerve, the main sensory nerve of the face and nasal cavity. When an irritant makes contact with the nasal mucosa, the trigeminal nerve transmits a signal to a coordination center in the brainstem.
This signal triggers a rapid, forceful expulsion of air from the lungs, designed to forcibly wash out the irritant from the respiratory tract. The urge to sneeze is generated by the activation of these nerve terminals, which detect the irritating nature of the vapor. The speed and intensity of the vapor’s irritants determine how quickly this protective reflex is initiated.
Common Chemical Triggers in Vapor
The liquid base of many cartridges contains Propylene Glycol (PG) and Vegetable Glycerin (VG), which are chemical irritants. Both PG and VG are hygroscopic, meaning they readily absorb water from their surroundings. When inhaled, these compounds draw moisture from the delicate mucosal lining of the nasal and throat passages, causing a drying effect that triggers the sneeze reflex.
Natural compounds called terpenes, used for flavor and aroma, are highly concentrated essential oils. When heated, terpenes can degrade into strong respiratory irritants such as aldehydes, including acrolein. Localized overheating can push terpenes past their thermal limits, producing a complex mixture of volatile irritants that activate sensory channels in the airways.
Flavoring additives also contribute to irritation, as certain specific compounds cause sensitivity. Aldehydes are also produced from the thermal breakdown of PG and VG, and they are classified as respiratory irritants. The presence of these concentrated, heated chemicals stimulates the nasal tissues, signaling a need for forceful expulsion.
Physical Factors and Inhalation Style
The temperature of the inhaled vapor is a physical factor that can prompt a sneeze. Hot vapor physically irritates the sensitive nasal and throat tissues more than cooler vapor. Localized overheating within the device can create micro-zones of intense heat that degrade components into volatile irritants, which are then carried into the airway.
The speed and force of inhalation also play a significant role in where the vapor is deposited. Taking a rapid, hard draw pushes the vapor deep into the nasal passages before it can cool. This aggressive inhalation forces irritating particles into contact with sensitive tissues, immediately triggering the sneeze reflex.
The physical size of the vapor particles also contributes to irritation. Ultrafine particles, formed from heated compounds, can deposit deeper within the respiratory tract and trigger the defensive reflex. This irritation is exacerbated if the user is dehydrated, as the hygroscopic nature of the base liquids intensifies the drying of the mucosal lining, increasing sensitivity.