The cause of many auto immune conditions is not clear. A combination of factors cause something to go wrong with the immune system. These factors relate to heredity, hormones, viral or bacterial infections, loss of immune tolerance or the nervous system.
The cause of Sjogren's is not clear either. The white blood cells, called lymphocytes, attack and damage the moisture-producing glands - mainly the tear and saliva glands. This causes dry eyes and dry mouth. Sometimes the skin, sinuses, airways and vaginal tissues are also affected, causing dryness in these areas. Sometimes the white blood cells damage other organs, including lungs, kidneys and liver.