The flu can indeed cause dry mouth. Dry mouth occurs when the salivary glands do not produce enough saliva to keep the mouth moist. This symptom is frequently temporary and is directly linked to the body’s physiological response to fighting the viral infection.
Systemic Dehydration Due to Illness
The primary cause of dry mouth during the flu is systemic dehydration, resulting from the body’s heightened metabolic state. When fighting a viral infection, the body often elevates its core temperature, causing a fever. This raises the metabolic rate and leads to increased fluid loss through sweating.
Fluid is also lost through increased respiratory effort as the body works harder to regulate temperature. Furthermore, the fatigue and lack of appetite accompanying the flu often lead to a significant reduction in fluid intake. This failure to replenish lost fluids depletes the body’s overall water supply. Since the body prioritizes fluid for immediate biological functions, less fluid is available for saliva production, reducing the output from the salivary glands.
The Role of Nasal Congestion and Mouth Breathing
Nasal congestion also contributes to dry mouth. The inflammatory response to the influenza virus commonly causes swelling and mucus buildup in the nasal passages, leading to a blocked nose. When the nasal passages are obstructed, the body instinctively switches to breathing primarily through the mouth.
Breathing through the mouth bypasses the natural humidification system provided by the nasal cavity. A continuous flow of dry air moves directly over the moist tissues of the oral cavity and throat. This constant airflow causes rapid evaporation of moisture from the lining of the mouth and the surface of the tongue, leading to the uncomfortable, sticky sensation characteristic of dry mouth.
Side Effects of Flu Medications
Certain over-the-counter medications used to manage flu symptoms can independently contribute to dry mouth. Specific classes of drugs, such as antihistamines and some decongestants, have a known drying effect on mucous membranes. Antihistamines, used to dry up nasal secretions, are the main culprits.
These medications often possess anticholinergic properties, meaning they block the action of acetylcholine, a neurotransmitter that stimulates saliva secretion. By interfering with this nerve signal, they chemically reduce the volume of saliva produced, regardless of hydration status. This common side effect can intensify the existing dryness caused by the illness itself.
Strategies for Relief and When to Consult a Doctor
Relief from flu-related dry mouth focuses on increasing systemic hydration and local moisture. The most effective strategy is to stay consistently hydrated by sipping water throughout the day, rather than drinking large amounts at once. Using a cool-mist humidifier, especially at night, can help by adding moisture to the air and reducing the evaporative effects of mouth breathing.
Sucking on sugar-free lozenges or chewing sugar-free gum stimulates the flow of saliva. It is helpful to avoid substances known to increase dryness, such as caffeine, alcohol, and tobacco products. While dry mouth is common during the flu, watch for signs signaling more serious dehydration. Seek medical attention immediately if dry mouth is accompanied by symptoms like:
- Extreme thirst
- Dizziness
- Confusion
- The inability to urinate for eight hours or longer