Dry Mouth: Causes and mechanisms


What causes dry mouth?

The causes of dry mouth

  • Taking medication is the number one cause1 of dry mouth as it is a side effect of many common medicines2,3
  • Taking multiple medications may increase the risk of dry mouth by 40%4
  • Other causes include conditions such as Sjögren’s syndrome, diabetes and salivary gland damage5,6

Salivary gland hypofunction

Dry mouth is associated with changes in saliva composition and may have no immediately identifiable cause.3,5 Salivary gland hypofunction – the objective measurement of reduced salivary flow – can be associated with:3,5,7,8

  • Medical treatments and polypharmacy
  • Lifestyle choices
  • Health conditions
  • Damage to the salivary glands
Salivary gland diagram

Salivary gland physiology

Three main salivary glands produce 90% of saliva.5 These glands produce the two major types of secretion that form saliva:5

  1. Serous fluid (mainly from the parotid and submandibular glands)
  2. Mucous (mainly from the submandibular and sublingual glands)
  • Salivary flow

    Salivary flow rate infographic and salivary flow decrease infographic

    Abnormal salivary flow can lead to dry mouth3,5

    Total salivary output should be approximately 1 litre per day, with salivary flow rates fluctuating naturally over this time.8 Patients may only realise that they have dry mouth when their natural salivary flow has decreased by almost half.8

  • Pharmacologic factors

    Polypharmacy and dry mouth risk infographic

    Medication use is the number one cause of dry mouth1,2,11

    Over 500 medications are associated with dry mouth,5,12 including many over-the-counter and commonly prescribed medications such as antihistamines, antidepressants, diuretics and cytotoxic drugs.1,2,11,13 Furthermore, the risk of dry mouth increases in people who take two or more medications.4,10

  • Other factors

    Other causes of dry mouth

    Besides medication use, there are various other physiological, behavioural, psychological and medical causes of dry mouth.

    Lifestyle factors
    • Mouth breathing5,11
    • Nasal obstruction5
    • Smoking11
    • Alcohol/drug abuse11
    • Caffeine11

    Medical treatments
    • Damage from radiation therapy for head and neck cancers2,3,5,11,12,14–16
    • Chemotherapy14,15
    • Physical trauma to the salivary glands3
    • Surgical removal of salivary glands5
    Community acquired infections
    • HIV-1 infection2,3,5,11,12,14,16
    • Hepatitis C2,5,12,13,16
    Psychiatric disorders
    • Anxiety5,14
    • Depression5,14,16
    Genetic disorders
    • Cystic fibrosis2,12,16
    Autoimmune diseases
    • Sjögren's syndrome1–3,5,11–16
    • Rheumatoid arthritis14,16

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