Lactic acid is a live active culture similar to the ones you find in yogurt, but not dairy related.
At Applegate, we use it as a natural preservative. The sugars used to create this lactic acid can be derived from beets or dextrose.
The lactic acid starter culture is not derived from wheat or dairy and does not contain any milk or milk protein. Therefore, the products are still considered to be gluten and casein free.