Vegetable glycerine is simply glycerine, also called glycerin or glycerol, that is derived from plant matter. Glycerine is easily isolated during the making of soap from animal fats, but it can also be obtained through processing of plants. Glycerine is a molecule that makes up the backbone structure of fats called triglycerides, and it is commonly used in foods, moisturizers, pharmaceuticals and other products. Vegetable glycerine is a sweet compound, but it is not a nutritive sweetener.Propylene glycol is similar in structure and properties to ethylene glycol, or antifreeze, but it is far less toxic to humans. Propylene glycol poisoning is rare, and the quantities of the substance that are necessary to cause poisoning are extremely high. Propylene glycol is an organic molecule with two alcohol groups on it. Propylene glycol is used as a safer antifreeze, in cosmetics, as a food additive and in other applications.

Both propylene glycol and vegetable glycerine have been approved by the FDA for various uses, including as food additives. Both substances have an extremely low toxicity, and have been labeled “generally regarded as safe,” meaning that no toxic effects or serious adverse effects occur at the levels at which these substances are consumed. Very little research has been done for the specific application of these substances in electronic cigarette e-liquid.

Because of vegetable glycerine’s sweetening properties, e-liquids made with this compound may have a different flavor. Some e-cigarette users seem to report sensitivity to propylene glycol, but this does not occur with vegetable glycerine. Propylene glycol-based e-liquids produce less vapor than those based on vegetable glycerine. Glycerine is a thicker substance, so the main downside to the compound is that it may reduce the life of your vaporizer.

Overall, some people may prefer vegetable glycerine-based e-liquids, and others may like the e-liquids based on propylene glycol. Both substances are generally safe and have a similar low risk profile, so choose your e-liquid based on your personal preference.

Produced under heat and pressure in chemical plants, Propylene Glycol is an organic chemical which is classed as a double alcohol. It has a range of uses, with approximately 20 percent of it going into food, drugs and cosmetics, according to the National Institute of Health’s PubChem database. It can be found in moisturizing eye drops, in asthma inhalers, in food products which need to remain moist, and as a smoke producer in both smoke machines and in e-liquid.

Although in extremely large quantities, Propylene Glycol can become toxic, in reasonable quantities, it is non-toxic. The only recorded death from ingestion of Propylene Glycol is a woman who drank two large bottles of antifreeze in a suicide attempt. The United States Food and Drug Administration has placed it on their list of food additives which are “Generally Recognized as Safe.” This list also includes basil, cornstarch and table salt (21 CFR Part 182).

Further proof of its safety comes from the Center for Disease Control’s December 2008 “Addendum to the Toxicological Profile for Propylene Glycol.” They went through a careful analysis of the risks of Propylene Glycol and confirmed that in extremely high concentrations, it can cause fatalities and decrease fertility in laboratory animals. However, upon a complete review of the chemical’s record, they concluded that Propylene Glycol presents a “minimal risk level.”

A large part of the concern about PG comes from a simple mix-up. It is common knowledge that antifreeze is typically extremely toxic. While PG is frequently used as a coolant and is present in modern “safe” antifreeze preparations, Ethylene Glycol is the toxic ingredient in many antifreezes. Although their names are similar, their risk profiles are completely different.

Ultimately, PG-based e-liquid is much safer than the alternative of smoking regular cigarettes. In fact, in 2009 the American Association of Public Health Physicians said that switching from cigarettes to e-liquid-using electronic cigarettes could reduce the risk of tobacco-related death by 100 percent. With this in mind, using Propylene Glycol e-liquid from a quality manufacturer is an extremely safe way to enjoy an electronic cigarette.