When I was 25 I got pregnant with my first baby. I found out I was pregnant as I was driving to college. I started throwing up uncontrollably and had to pull over. I drove straight to the grocery store for a pregnancy test. Over the next 3-4 months I kept throwing up, practically everything made me sick, but specially milk. After I had my baby I was very excited to be able to drink milk again and eat cereal. After the first bite and drink I ran to the bathroom and threw-up. Later I would get severe stomach aches, frequently, and by severe I mean it felt like a knife was ripping my stomach apart. The pain was so unbearable I could hardly breath and thought I would die. Symptoms vary depending on how severe a person is--from simple stomach aches, bloating, gas, to throwing up or diarrhea. Practically any food which has any kind of dairy has lactose which is a type of sugar. This is why many products now say contains "milk" or check the ingredients. Over time some people loose the enzyme in their digestive tract which breaks down this sugar, and that is lactose intolerance.