Do electronic cigarettes need a hechsher since the liquid is flavored?
It is difficult for me to answer such a question, because the premise that one is permitted in the first place to use an electronic cigarette is not so simple. Smoking is damaging to one’s health, and many poskim hold that it is assur to smoke, as one is obligated from the Torah not to do anything that will damage his health. One should think twice before smoking if this is the proper thing to do.
Regarding whether they need a hechsher:
Many poskim hold that the liquid does need a hechsher. We find that steam from a food is considered like the food itself–for example, if steam from meat would touch milk it would be assur. Therefore, here one is inhaling the steam of the liquid, and is as if one is eating the liquid itself, and therefore it needs a hechsher. However, there are some poskim that hold that it doesn’t need a hechsher. The bottom line is that one should certainly use only with a hechsher if possible.
Rabbi Moshe Shoul Klein, Rabbi Moshe Sternbuch, Rabbi Ezrial Auerbach.
גליון מאיר דרך (גליון כ, כג), גליון עומק הפשט (גליון 206)