This is a feasibility study that will assess the efficacy of using autologous blood to treat moderate to severe dry mouth. Dry mouth has been estimated to affect up to 64.8% of the general population (Navazesh et al., 2009) and many patients that are affected by Sjögren's syndrome or have had radiation therapy to combat head or neck cancer (Navazesh et al., 2009).

The blood will be applied to the interior of the mouth by means of a mouthwash. This research poses the first potential curative treatment for dry mouth - all other current dry mouth treatments are either symptomatic or lifestyle-based.

Autologous blood has been shown to be effective in treating the epithelial surface of dry eyes. This has been attributed to the analogous growth factors in the blood to that of tears - and potentially in this case, saliva - in healing the oral epithelial surface (Herbst et al., 2004).

Fingerprick autologous blood (FAB) has been demonstrated to be effective in treating dry eye disease by inducing healing of the epithelial surface of the eye (Than et al., 2017). The epithelial layers of both the mouth and the eye require a non-vascular source of lubrication and nutrients (tears and saliva respectively). These nutrients include growth factors - naturally occurring substances capable of stimulating cellular growth. Saliva provides transforming growth factor alpha (TGF - α) (Mogi et al., 1995), epidermal growth factor (EGF) (Herbst, 2004; Marti et al., 1989), and Hepatocyte growth factor (HGF) (Amano et al., 1994) whilst tears provide EGF (Ohashi et al., 1989) amongst others (including TGF -β 1 and 2 (Gupta et al., 1996) integral to the proliferation, survival and differentiation of the oral epithelial cells (Klenkler et al., 2007). Therefore, as severe dry mouth disease (and a subsequent lack of saliva and growth factors) causes damage to the epithelial surface lining the mouth, a growth factor rich saliva substitute like FAB, should be an effective treatment for dry mouth. There is currently no study which details FAB for use in dry mouth.

Whole or parts of the three major salivary glands have been surgically transplanted or redirected to provide a replacement tear film in patients with severe dry eyes. This has been shown to be successful in both lubricating and improving eye comfort in afflicted patients (Geerling & Sieg, 2008). Since both blood and saliva have been shown to be effective as tear substitutes, it stands to reason that both tears and blood may be effective as a saliva substitute. Both tears and saliva are extraordinarily complex blood derived biological products which provide nourishment to an epithelial surface, and as such, blood should serve as a sufficiently close mimic of saliva.

Sjögren's syndrome, a chronic systemic autoimmune disease, occurs due to infiltration of secretory (exocrine) glands including the eye and mouth, resulting in dry eye and mouth respectively. FAB has been shown to be effective in treating Sjögren's induced dry eye and logically should also be an efficacious treatment for Sjögren's induced dry mouth.

Currently no curative measures for dry mouth exist. Oral dryness is managed conservatively by providing lubrication through a temporary solution such as lifestyle changes, artificial sprays, dry mouth mouthwash solutions or sialagogues (Shirlaw & Khan, 2017). There is no treatment that addresses the complexity of salivary constituents. Oral pilocarpine can be used to stimulate salivary glands at least as effectively as artificial saliva, however side effects were high including sweating, urinary frequency and vasodilation (Davies & Thompson, 2015).

Thus, FAB offers a potentially novel and better way than currently prescribed methods to treat dry mouth disease.

Inclusion Criteria:

- Patients diagnosed with dry mouth and are on or have refused treatment e.g. spray or mouthwash

Exclusion Criteria:

• Patients who do not have capacity to consent
• Patients with immunodeficiency
• Infected finger or systemic infection or on systemic antibiotics for infection
• Patients with active microbial infection, acute herpes simplex, herpes zoster or infected mouth ulcers
• Pregnant or breast feeding women
• Fear of needles and unwillingness to carry out repeated finger pricks
• Patients with frank oral ulceration