Dry mouth, or xerostomia, occurs when the salivary glands fail to produce enough saliva to keep the mouth moist. Saliva acts as a natural lubricant and protective barrier for the mucous membranes of the mouth and throat. When this protective lubrication is compromised, tissues become vulnerable to irritation, which can lead to a persistent, often dry, cough.
The Physical Mechanism Behind the Cough
Saliva normally coats the mucous membranes lining the pharynx and larynx, creating a smooth, protective layer. This layer shields the tissues from the constant friction of speaking, breathing, and swallowing. Reduced salivary flow causes throat tissues to dry out, leading to a sensation of scratchiness or rawness.
The body interprets this unnatural dryness and subsequent irritation as a foreign irritant that needs to be cleared. This triggers the involuntary cough reflex, a neurological response designed to expel foreign matter from the respiratory tract. The resulting cough is frequently non-productive, meaning it does not bring up mucus, and is often described as a dry, hacking tickle in the throat.
This lack of moisture can also lead to hoarseness because the vocal cords require a thin layer of fluid to vibrate efficiently. Chronic irritation and dryness cause sustained inflammation in the throat, which perpetuates the cough cycle. Since the underlying cause is dryness rather than infection, this type of cough often resists typical cough suppressants.
Underlying Factors That Cause Dry Mouth
The causes of xerostomia are numerous, with the use of certain medications being the most common factor, particularly in older adults. Hundreds of prescription and over-the-counter drugs have a xerogenic effect, meaning they interfere with saliva production. Medications with anticholinergic or sympathomimetic properties, such as antidepressants, antihistamines, decongestants, and blood pressure drugs, are frequent culprits.
Systemic health conditions can also impair salivary gland function. For example, the autoimmune disorder Sjögren’s syndrome targets and damages moisture-producing glands, commonly causing both dry eyes and a persistent dry cough. Diabetes can also lead to xerostomia due to changes in fluid balance and nerve function.
Lifestyle and environmental factors contribute significantly to mouth dryness. Chronic dehydration reduces the body’s ability to produce saliva, as saliva is approximately 99% water. Breathing through the mouth, especially while sleeping due to nasal congestion, accelerates the evaporation of moisture. Tobacco use, whether smoking or chewing, is also a known irritant that decreases salivary flow.
Strategies for Alleviating Dry Mouth and Coughing
Management of dry mouth and the associated cough begins by addressing the underlying cause. If medications are suspected, consult a healthcare provider to adjust dosages or switch to a less xerogenic alternative. Never stop taking prescribed medication without first speaking to a doctor.
To immediately increase comfort, sip water frequently throughout the day to maintain a constantly moist environment. Chewing sugar-free gum or sucking on sugar-free lozenges, particularly those containing xylitol, can stimulate residual salivary flow. Specialized saliva substitutes and moisturizing sprays, often containing carboxymethylcellulose, can coat and lubricate the mouth and throat tissues.
Environmental adjustments, such as using a cool-mist room humidifier at night, counteract the drying effect of indoor air. Avoiding substances that act as diuretics or irritants is also beneficial, including limiting caffeine, alcohol, and all forms of tobacco. If symptoms persist, seek an evaluation from a physician or dentist to rule out complex underlying conditions, such as Sjögren’s syndrome, which may require specific medical treatment.