Although lox comes from salmon, a kosher fish, not all lox is kosher. This is because certain manufacturers mix non-kosher ingredients in to the lox. For example, some companies use lard to give the lox its shiny appearance and smooth texture. So, as with all processed foods, only buy lox that is certified as kosher.

I hope you find this information useful.

With wishes for a happy Chanukah,

Rabbi Eliezer Posner