The e-cig itself (I.e., the hardware) has no recipe. It is just an electronic device for vaporizing the liquid put in it. I suspect that you are referring to the cartridges that will come with your starter kit. Those will be prefilled with menthol or "regular"-flavored
e-liquid.
Almost certainly, that e-liquid was manufactured in China (as was the e-cig), probably by Dekang or it subsidiary, Boge. Only a portion of the "after-market" e-liquid is U.S.-made.
The main ingredient in all e-liquid is propylene glycol (PG). [Or VG, described below.] Into that is mixed your selected amount of nicotine (derived from tobacco) and flavoring. The nicotine extraction process and flavoring ingredients are often protected as trade secrets.
According to the Veppo website: "Our
eliquid is made from only the purest raw ingredients and flavored with approved food-safe flavorings and natural flavors." That sounds reassuring, but is not very specifc.
So ... that was my long-winded way of saying: "I don't know.". I can tell you that I don't of anyone who has become seriously ill from
vaping Dekang e-liquid. [Some people are alergic to PG. They should switch to liquid with a vegetable glycerin (VG) base, available from many of the suppliers represented here on ECF.]