The one I use has non-fat dry, milk in it. I wanted to get the plain version without any strawberry flavoring, but they did not have it in stock. I saw the plain kind before, and it looked like a lab experiment with all these different strains of bacteria floating around. It might be easier/less gross to use when the bacteria looks uniform as in the yogurt form (the flavored kind). It probably tastes better, too.
Since different acidophilus liquids have varing types of bacteria, I do not know if it matters which strains of bacteria are in it. In an earlier post under "I think my lips might be healed" I wrote the different types of bacteria in the liquid I use. I also take acidophilus supplements for my intestines (those do not help with mouth, though), but some brands (or strains of bacteria) work better than others.
I used it once per day after I brushed my teeth in the morning (after eating breakfast). I swished it all around my mouth and spit it out. Then you should apply it directly to your lips. It will air dry after a couple minutes. Just keep it on, and don't wash it off. It does not dry sticky. Although I only used it once per day, I recommend others to use it after every meal.