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Ruth,
Tequila is made out of a plant called "agave azul tequilero" which is
an "Agavacea". Real tequila does not contain any gluten. But beware
becuase fake tequilas can have another liquor from an unknown origin.
The bottle must say: "100% agave azul" and "Embasado bajo la
supervisión del Gobierno Mexicano" to be real tequila.
Here is a list of tequilas that are real:
-Herradura
-Don Julio
-Jimador
-Porfirio
-Cuervo tradicional
-Siete Leguas
-Hornitos
-Xalisco
-Dos amigos.
I don't know if they can be found in the U.S.

Salvador Arroyo.