The intense stinging sensation accompanying many mouthwashes is often described as a “spicy” or burning feeling. Many brands advertise this reaction as a sign that the product is actively eliminating germs. However, the burn is not a true chemical burn or a sudden spike in temperature. Instead, this intense feeling is a temporary physiological response resulting from specific chemical ingredients interacting with the sensory system inside the mouth.
The Chemical Components Causing the Heat
The most potent source of the mouthwash burn is ethanol, commonly known as alcohol. Traditional formulas use alcohol primarily as a solvent to keep active ingredients, often oils, uniformly mixed. Concentrations can range significantly, sometimes reaching 20% to 27%, which is high enough to irritate the delicate soft tissues of the mouth.
Essential oils also contribute to the sensation. These oils, such as eucalyptol, thymol, and menthol, are included for their antiseptic and flavor properties. Menthol, in particular, provides the characteristic minty freshness but also agitates nerve endings, which the brain interprets as a burn or strong tingle.
How Oral Sensory Receptors Interpret the Burn
The sensation of heat or spiciness is a phenomenon known as chemesthesis, where chemicals stimulate the pain and temperature receptors in the mouth. This process involves specialized proteins called Transient Receptor Potential (TRP) channels. The most relevant is the TRPV1 receptor, often called the capsaicin receptor because it is activated by the compounds found in chili peppers. When mouthwash ingredients, particularly ethanol and essential oils, activate TRPV1, the brain receives a signal identical to one caused by actual heat.
The brain perceives a burning sensation, even though no physical damage occurs. Menthol adds another layer to this experience by activating the TRPM8 receptor. TRPM8 is responsible for sensing cold and makes mint feel cool or icy. The simultaneous activation of the “hot” TRPV1 receptor and the “cold” TRPM8 receptor creates the complex sensation of a sharp sting combined with a cooling rush.
Reducing the Sensation and Alcohol-Free Alternatives
If the burning sensation is too intense or uncomfortable, simple adjustments can alleviate it. One method is to temporarily reduce the concentration of the mouthwash by diluting it with water before rinsing. Users can also reduce the duration of the rinse, holding the liquid for a shorter period than recommended.
Switching to an alcohol-free formula is the most effective way to eliminate the burn, as it removes the primary irritant. These alternatives often utilize different antiseptic agents, such as cetylpyridinium chloride (CPC). CPC provides antibacterial action without triggering the painful nerve receptors. If the sensation is persistent or causes significant discomfort, consulting a dentist is advisable to rule out underlying oral sensitivity issues.