They are from animal sources, but I am not quite sure which. Gel caps are sold as regular (animal) or veggie. AX doesn't use the veggie ones. When in doubt, dump the contents out.
Just make sure to drink a lot of fluid when you do that so that it all washes down. Certain things can really burn up the throat.
-If you need any additional information... I am sure Tim can and will grace us with his presence.