No matter how much I drink throughout the day, my mouth is uncomfortably dry, and it's getting worse. My eyes have been dry and itchy lately, too, but I haven't had other allergy or cold symptoms. The ones usually responsible for dry mouth include decongestants, diuretics , antihypertensives, antidepressants and antihistamines. If you are taking one of these drugs, your best bet is to ask your doctor or pharmacist to suggest a substitute that doesn't cause dry mouth. 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.