Lactose Intolerance Symptoms and causes?

I have got a kind of non digestive problem towards lactose since my childhood itself. Whenever I consumed milk products I tend to throw it out. Now I have developed some tastes for milk products but fear of indigestion keeps me away from its consumption. I wish to know about all the Lactose Intolerance Symptoms and what are the causes of this lactose intolerence. I also wish to know about all those meausres by which it could get cured.