A dry mouth: Causes and Mechanisms


Recognising the underlying causes of a dry mouth in your patients

Although medication is one of the most common causes of a dry mouth, other causes can lead to reduced saliva flow.

Causes of a dry mouth

  • Taking medication is one of the most common causes of a dry mouth as it is a side effect of many common medicines2,3
  • 40% of patients taking multiple medications at once may experience a dry mouth4

Other causes include conditions such as Sjögren’s syndrome and salivary gland damage5,6

Salivary gland hypofunction

A 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)
Flow rate infographic

Certain stimuli can change the saliva flow rate and cause a dry mouth7

The autonomic nervous system (ANS) controls the volume and type of saliva from these glands and maintains a steady flow.7Different stimuli may increase or decrease the rate of this flow.7

The different causes of a dry mouth

  • Salivary flow

    Salivary flow rate infographic and salivary flow decrease infographic

    Abnormal salivary flow can lead to a dry mouth3,5

    Total salivary output is estimated to be approximately 1 litre per day, with salivary flow rates fluctuating naturally over this time.8 It may only become apparent that a patient has a dry mouth when their natural salivary flow has decreased by almost half.8

  • Pharmacologic factors

    Medication use is one of the leading causes of a dry mouth1,2,11

    Over 500 medications are associated with causing a 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 experiencing a dry mouth increases in people who take two or more medications.4,10

  • Other factors

    Other causes of a dry mouth

    In addition to medication use, there are various other physiological, behavioural, psychological and medical causes of a 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

Biotène – helping your patients manage a dry mouth

Family icon

Impact on patient quality of life

Find out about the impact that a dry mouth has on patients’ daily lives


Tooth Magnified icon


Explore an overview of signs of a dry mouth


Dentist icon


Explore an overview of managing a dry mouth


Dry mouth icon

A dry mouth

Find out more about a dry mouth.


Biotene logo

The Biotène range

Find out how the Biotène range can help your patients.


Patient resources icon

Patient care resources

Download resources for your patients.