Symptoms of lactose intolerance can vary in severity. In my case, I can tolerate a small amount of milk/dairy products on a daily basis, but if I exceed that amount, whooo, don't I know it! Gassiness, bloating, frequent visits to the bathroom...
Imodium. YESSSSS! The lactose intolerant person's friend....
And, yes, for many years I didn't really understand why it was that drinking a chocolate milkshake would give me problems but a simple cup of yogurt would be OK. When I was in a situation where suddenly I was eating much more dairy than I was accustomed to doing, the problem surfaced big-time and finally, with the help of a registered dietitian the cause was identified. I then experimented to find the amount of dairy that is comfortable and safe for me and as long as I'm mindful of that, I'm fine.