The most common presentation of salivary glands diseases is xerostomia defined as a subjective complaint of dry mouth with a relative prevalence of 13.2% in the general population (Orellana et al., 2006, Jamieson and Thomson, 2020). Hyposalivation refers to a quantified reduced salivary flow rate that may or may not be accompanied by xerostomia. Similarly, xerostomia may or may not be associated with hyposalivation and may be its result. The causes of salivary gland hypofunction include xerogenic medications and other agents (e.g., caffeine, alcohol, cigarette smoking), head and neck irradiation, systemic diseases (e.g., diabetes mellitus, chronic renal failure), salivary gland masses, psychological conditions (e.g., depression, anxiety), malnutrition (e.g., bulimia, dehydration), autoimmune diseases (e.g., SS), and other unspecified or undiagnosed conditions (Glick, 2015).

Xerostomia is one of the most common oral manifestations of chronic renal failure, which occurs due to decreased fluid intake and salivary gland changes in these patients. Other oral manifestations of chronic renal failure include dysgeusia, stomatitis, decreased salivary flow rate, and parotitis; moreover, dental conditions include narrowing of the pulp chamber, enamel abnormalities, tooth loss, and periodontal disease. Hemodialysis improves most of the oral symptoms of End Stage Renal Disease (ESRD), but uremic odor, dry mouth, taste change, and pain in the tongue and mucous membranes are the symptoms that persist in many patients (Haider et al., 2013a).

The role of saliva in maintaining the health of the soft and hard tissues of the mouth includes washing toxic materials from the oral cavity, adjusting acidity, buffering decalcifying acids, neutralizing toxins and bacterial enzymes, destroying microorganisms, and remineralizing the enamel with its minerals like calcium and phosphorus. Reduction and lack of saliva cause several problems for patients. (Satvati and Sharifi., 2016) Patients may complain about the dryness of all of the oral mucosal surfaces, including the lips and throat, and difficulty chewing, swallowing, and speaking (Glick, 2015).

Treatment of salivary hypofunction and xerostomia is primarily palliative using several approaches such as the use of chewing gum (Karami et al., 2011), sugar free lozenges (Dalodom et al., 2016), mucosal lubricants, saliva substitutes, and saliva stimulants (Villa et al., 2015). There are several topical and systemic salivary stimulators such as acupuncture, pilocarpine HCl, and cevimeline HCl (Glick, 2015).

Some traditional medicines that are used in different countries to improve dry mouth include Korean red ginseng (Park et al., 2010, Kim et al., 2018), Yukmijihwang-tang in South Korea (Han et al., 2013).

There are several studies on the use of chewing gum to improve the symptoms of dry mouth in hemodialysis patients (Ozen et al., 2021, Duruk et al., 2016), which indicate an increase in salivary flow rate and quality of life (Fan et al., 2013), while in the study of Jagodzińska et al in 2011, the patients did not report experiencing any changes in the intensity of xerostomia and thirst.

Ginger (Zingiber Officinale) belongs to the Zingiberaceae family. The consumed part of the ginger plant is the rhizome, which is often called the "ginger root". The ginger is an important medicinal plant with several properties including antibacterial, anti-nausea and vomiting, anti-inflammatory, anti-flatulence, anti-blood clotting, heart tonic, antioxidant, anti-inflammatory, antispasmodic, immune system stimulation, digestion stimulatory effects. (Ali et al., 2008, Bode and Dong, 2011) In 2011, Chamani et al. showed the sialogogic effect of ginger in rats. (Chamani et al., 2011) Other studies on the effect of ginger on salivary secretion in patients with dry mouth have shown positive results. (Chamani et al., 2017, Chamani et al., 2017, Mardani et al., 2017, Satvati and Sharifi, 2016) This sialogogic effect of ginger seems to be due to its parasympathetic properties. (Muhammad et al., 2007) Therefore, the present study was conducted to investigate this relationship in more detail.