Babies are born with the lactase enzyme and most lactose intolerance does not occur until age 3 or older if at all. As people age, they can lose the lactase enzyme. Symptoms can be bloating, cramps, diarrhea
and poor growth
. Some races such as asians and african americans are more susceptable to lactose intolerance than caucasians.
A pretty good way to tell whether you are lactose intolerant is to stop eating dairy and see if your symptoms improve. Then, restart eating dairy and see if they return. If you enjoy milk and other dairy, you can try using "lactaid" products that already have the lactose component broken down or there are lactase supplements
you can take prior to eating dairy.