Your condition could also be due to an autoimmune disease like rheumatoid arthritis or Sjogren's Syndrome or to other conditions like diabetes and Parkinson's disease or possibly to radiation therapy. Anxiety can also be the cause, as can simply getting older. If you are having trouble chewing, that, too, can lead to dry mouth. An allergy might be responsible for your dry, itchy eyes but not for your lack of saliva. More than just an uncomfortable annoyance, dry mouth can cause serious dental problems.
Saliva impedes the accumulation of plaque on and between teeth.
Decreased saliva favors the buildup of plaque, increasing risk of tooth decay and gum disease. Sip water frequently during the day, and keep a glass of water at your bedside at night. A little lemon juice added to your drinking water should stimulate saliva flow. Avoid both salty and sugary foods. Chew sugarless gum.