A good probiotic is essential for IBDers cuz we tend to have bacterial over-growth, so flaring or not, a good probiotic should be taken daily...one that contains a minimum of 10 billion live cultures is best, anything that contains more and various strains is even better.
Yogurt naturally has the lactose broken down in it so it shouldn't cause issue for lactose intolerance (which I was severely until I started taking probiotics daily and indefinitely)...if you have lactose issues and yogurt is still an issue then it may actually be casein found in dairly products and an allergy rather than a lactose issue. You can get tested for either or both.
2 Really great probiotics are one called Primadophilus Reuteri made by natures way which has guaranteed intestinal release, aids with lactose issues, high cholesterol and for women, vaginal health. Another comparable to the Primdadophilus is one called ProBioTX-11 made by Sangsters, it's a little better cuz it contains 10 billion live cultures in one cap, the PR contains 5 but it's still a good one, the ProBio is better priced cuz it's Sangsters Health Food store brand...both must be kept refridgerated.
Whether you notice a difference in your IBD symptoms or not, it's still a good idea to take a good probiotic daily, you might be surprised that it may at least keep your current symptoms from getting worse if nothing else. It also varies for each person as to how long it takes for a good probiotic to kick in.