Culturelle contains Lactobacillus GG, an extensively studied strain of friendly intestinal bacteria, naturally occurring in the digestive tract. Lactobacillus GG is a specific strain of the species Lactobacillus rhamnosus, discovered and patented by researchers Drs. Gorbach and Goldin at Tufts University. To date, this is the best-studied and most extensively documented probiotic lactic acid bacteria strain in the world.* Dairy-free and gluten-free.