Howard Feldenkreis of Purity Farms, Inc wrote back to me:

Dear Susan
Thank You for writing to us! Yes, every batch of our Ghee is tested
in an FDA certified lab to insure that it is lactose and casein
free....Therefore we can put on our label that our Ghee is,indeed, lactose and casein free-it is fine for people with even the most severe dairy allergies.
Happy Cooking! Kathy-Purity Farms, Inc.

Clark-Lindh wrote:

> Hello,Please tell me how you make the claim for lactose-free and
> casein-free Ghee.Do you have a third party test like the ELISA
> standard test for gluten-free?I am very interested in your Ghee, but
> need to ensure it has been batch tested in some way.Thank you so much
> for your attention to my query.Susan
>
> --