Seasonal allergies result from an immune response to airborne substances like pollen, leading to symptoms such as sneezing, a runny nose, and nasal congestion. Dry mouth (xerostomia) is the subjective feeling of having insufficient saliva. The body’s reaction to allergens directly and indirectly affects oral moisture levels, creating a clear link between seasonal allergies and dry mouth.
The Congestion-Mouth Breathing Connection
Allergic inflammation is the first step in the physiological chain that leads to dry mouth during allergy season. When the immune system encounters allergens, it releases chemicals that cause the tissues lining the nasal passages to swell, a condition called nasal congestion. This swelling obstructs the normal flow of air, making breathing through the nose difficult or impossible.
When nasal airflow is blocked, the body instinctively switches to mouth breathing to maintain oxygen intake, often without the person realizing it. This shift in breathing patterns dramatically increases the rate at which moisture evaporates from the oral cavity. Saliva evaporates quickly as air passes constantly over the tongue and other oral tissues.
Saliva plays a necessary role in the mouth, lubricating tissues, aiding in digestion, and neutralizing acids to protect teeth. A consistently dry mouth environment, caused by prolonged mouth breathing, leaves the oral tissues vulnerable and feeling sticky or parched.
Antihistamines and Xerostomia
Beyond the physical effects of congestion, the medications commonly used to treat seasonal allergies can also cause dry mouth. Antihistamines, particularly the older, first-generation versions, are a frequent cause of xerostomia. These drugs often possess anticholinergic properties, meaning they interfere with the signaling of acetylcholine, a neurotransmitter in the nervous system.
Acetylcholine is the primary chemical messenger that stimulates the salivary glands to produce and secrete saliva. Anticholinergic drugs block the muscarinic receptors on the salivary glands, interrupting the nerve impulse that triggers saliva flow. This disruption results in a significant reduction in the volume of saliva produced, leading to a dry mouth regardless of nasal congestion.
The newer, non-drowsy second-generation antihistamines were formulated to have fewer anticholinergic effects, but the risk of dry mouth is still present for some individuals. When multiple medications with anticholinergic properties are taken simultaneously, the drying effect can be cumulative and more pronounced.
Strategies for Managing Dry Mouth
Drinking water frequently throughout the day helps to keep the mouth hydrated and temporarily relieves dryness. Sipping water, rather than gulping, is more effective for maintaining moisture.
Chewing sugar-free gum or sucking on sugar-free lozenges or hard candies can physically stimulate the salivary glands to produce more saliva. Using a humidifier, especially at night, adds moisture to the air and can reduce the evaporative effects of mouth breathing during sleep.
For persistent dry mouth, over-the-counter saliva substitutes, which come in sprays or gels, can coat the mouth and provide temporary relief. Individuals who find their dry mouth symptoms severe or persistent should talk to a doctor or dentist about prescription options. These professionals can recommend stronger lubricating gels or, in some cases, prescription medications that directly stimulate saliva production.