Am I lactose intolerant?

Can you be selectively lactose intolerant?

• I'm a 21 year old male. My dad is lactose intolerant... he can't eat ANYTHING dairy. I on the other hand, think I am only selectively lactose intolerant, and I'm wondering if anyone else has experience with this or knows if this is possible. I've been searching for answers but can't find anything in medical journals online or experience-based. I can drink milk or eat cheese if I've had enough sleep and am generally healthy. I can digest yogurt, sour cream, butter and most ice creams just fine. Every now and then though (like once every couple months) I'll get horribly sick from cheese on a pizza or a bowl of ice cream. I have horrible diarrhea (gross, I know...). It's weird because I eat pizza maybe once every couple weeks, and (if I've got sleep and am healthy) I'm fine with digesting it. Same with ice cream. Does anyone know if it's possible to be selectively lactose intolerant, or what would cause it? Should I see a doctor about this or be taking some kind of over the counter medication? Stories from other lactose intolerant individuals appreciated.

• Answer:

  That's odd, but it makes sence. Lactose intolerant people tend to lack a certain enzyme used to break down the lactose molecule in their foods. It's likely that your body still makes the enzyme, but isn't very good at it. That could explain why a rested/healthy you has the ability to make enough enzymes, but a tired, worn out you can't. Same concept as the common cold. If you aren't sleeping enough or taking care of yourself, your immune system looses strength, and you're more succeptible to getting a cold. OTC medicines usually work for people, although for how long it's hard to say. At your relatively young age, it's very possible you will develop symptoms like your father later in life. Stupid genetics.