Hello -- Very few brands of commercially-produced lactose, and no brands of butter, are actually casein-free. Most commercially-produced lactose is MOSTLY free of casein, but it's expensive to get that last bit of casein out of the lactose, so most places don't bother. WHy? Because for most purposes a little bit of casein won't matter. (Think about when you separate eggs, retaining just the yolk. A little bit of white always remains with the yolk, but for cooking purposes that little bit of white doesn't make a difference.) For people with a casein allergy, though, that little bit of leftover casein can make a HUGE difference, and therefore products with lactose in them are NOT recommended. (If your reaction isn't life threatening, feel free to experiment, of course.) Similarly, butter is composed primarily of dairy fat. However, much of the taste of butter comes from everything BUT the fat in dairy, including casein. I don't know of anyone with a casein allergy who can go near butter safely. You can, of course, try clarified butter (ghee), but you should do it yourself, rather then purchasing a commerically-available variety, to make sure that ALL the casein is really clarified out. (There was a thread about ghee a couple of years ago that you may be able to find... It explained the procedure and the risk.) I would not trust any company that said its lactose was completely casein-free. Ask instead for the brand of lactose that they purchase and talk to the lactose supplier directly. You'll probably discover that some casein is, in fact, left in because it makes commercial sense to do so. I hope this helps, --Beth Kevles [log in to unmask] http://web.mit.edu/kevles/www/nomilk.html -- a page for the milk-allergic Disclaimer: Nothing in this message should be construed as medical advice. Please consult with your own medical practicioner. NOTE: No email is read at my MIT address. Use the AOL one if you would like me to reply.