Is lactose intolerance painful?

It can be. Depending on the severity of your lactose intolerance and how much dairy products you consume without lactaid support, you may have periods of abdominal discomfort/ pain.
Gas. I agree with dr erkine, but i want to add that often it is not at all painful. Many times people just have excessive gas and flatulance, which may not be painful, but may be embarrassing.

Related Questions

Why is gas caused by lactose intolerance so painful?

Gas. Gas produced by lactose intolerance affects individuals differently.In some people the pain may be severe, in others the pain may be mild. Read more...
Malabsorption. You have ingested a substance that your body is having difficulty of absorbing or breaking down; lots of gas is formed in a short period of time making an intense stew of gas in your intestine. Ouch! Read more...