Propylene glycol is found in cosmetic products, in antifreeze, and in your food. That list does not inspire confidence in those who want to be sure they're eating all-natural foods that are healthy and nutritious. What is propylene glycol, and how is it useful in personal care products like deodorants and yet still considered safe enough to be a food additive? Are there side effects to consuming propylene glycol that you need to be aware of? We have all of those answers here.
What Is Propylene Glycol?
According to food safety experts in Europe and at the U.S. Food and Drug Administration (FDA), propylene glycol is safe to consume. It's a synthetically made food additive derived from glycerin, and it's in the same chemical category as alcohol. However, many of us know that alcohol is a poison, and plenty of substances are deemed safe to consume even when they are proven bad for us (like high-fructose corn syrup).
Propylene glycol is also syrupy, but colorless and odorless, making it a convenient additive as a thickener in many commercial products, keeping pre-packaged foods moisturized. If you're looking for it in nutrition labels, it may be listed under the names:
- Trimethyl glycol
- Methyl ethyl glycol
Propylene glycol is not ethylene glycol, though they are often confused because both are contained in antifreeze. Ethylene glycol is toxic to human beings, and will not be found in food or personal care products.
How Is Propylene Glycol Used?
Propylene glycol is in many foods as a preservative to help extend the shelf life of certain products, but what else is it doing? Here's a list of propylene glycol uses and the types of products it's frequently found in.
- Emulsification: In foods like salad dressings, propylene glycol can help keep oil and vinegar from separating.
- Anti-caking: In dry food items like grated cheese or soup mixes, propylene glycol prevents clumping and caking of the ingredients.
- Thickener: For stabilizing and thickening items like foods and personal care products, propylene glycol can hold together looser ingredients to keep them from crumbling.
- Antioxidant abilities: Most people know antioxidants as vitamins that prevent oxidative stress damage in our bodies, but propylene glycol can act as an antioxidant in foods, preventing their deterioration before we eat them.
- Visual appeal: Propylene glycol may be used to enhance the appearance of a food, for example, to make a liquid look clearer.
- Carrier: In pre-mixing flavorings and colors, propylene glycol is sometimes used for dissolving these substances into a liquid form before adding them to our food or to beverages like soft drinks.
- Stabilizer: Propylene glycol helps to modify the gluten and starch in doughy food products to make them more stable.
- Moisturizing and texturizing: Propylene glycol is included to preserve the moisture in foods like marshmallows and to improve the texture and "mouthfeel" of food.
Not just a food additive, propylene glycol is also found in injectable medications (like lorazepam), as a humectant (moisture stabilizer) in beauty creams and hair care products, in corticosteroids, artificial smoke and fogs used in theatrical productions, e-cigarettes, paint, antifreeze, and topical ointments.
Is Propylene Glycol Safe?
Now you have an idea of just how widespread propylene glycol is in foods and medications, so what about the safety data? The FDA and the Federal Agency for Toxic Substances and Disease Registry in the United States have labeled and accepted this substance as “generally recognized as safe” or GRAS. However, the World Health Organization recommends that humans limit their intake to 11.4 milligrams per pound of body weight each day to avoid toxicity. With propylene glycol in so many food products, what happens when you get too much of it?
The Toxicological Profile of Propylene Glycol
Propylene glycol is extremely safe in humans. The one case of toxicity and poisoning from a food product on record involved a man drinking extremely large amounts of cinnamon whiskey that contained propylene glycol. It takes over 100 times the amount of propylene glycol found in an average diet to cause any harm whatsoever, outside of those who have an allergic reaction to the effects of propylene glycol.
Adverse Health Effects of Propylene Glycol
While overdosing on propylene glycol is nearly impossible, there are some concerns about it affecting underlying health conditions. With a very low toxicity, it's nevertheless true that some people are more susceptible to high doses (like those found in medications). At-risk populations who may want to avoid propylene glycol include the following groups.
People with Liver or Kidney Disease
Under normal circumstances, propylene glycol is quickly broken down and removed from the body, but in cases of liver or kidney disease, propylene glycol breakdown can lead to lactic acid buildup in the blood (lactic acidosis). Those with kidney damage and taking lorazepam have shown symptoms of toxicity like throat swelling and shortness of breath, and critically ill patients given lorazepam also exhibited signs of propylene glycol toxicity, but only in 19% of cases.
Pregnant Women and Infants
The enzyme alcohol dehydrogenase is needed for propylene glycol breakdown, and it is lower in pregnant women, infants, and children under 4. Without being able to process the substance as well as adults, infants are particularly at risk if they are injected with vitamins containing large amounts of propylene glycol, which has led to instances of seizure.
Vulnerable populations including young children or pregnant women may be at risk from high amounts of propylene glycol in vitamins, but there is no research indicating dangerous levels could be gained from consuming foods as part of a normal diet.
Those with Risk Factors for Heart Attack
High amounts of injected propylene glycol may cause a dangerous drop in blood pressure, interrupt heart rhythms, and put certain people in danger of experiencing a heart attack. A loss of heart function was found in two cases of children administered silver sulfadiazine cream and another who was injected with vitamin C dissolved in propylene glycol.
People with Neurological Conditions
Cases have shown dangerous interactions between propylene glycol and people with epilepsy and other neurological conditions. These were again in clinical settings with very high doses of propylene glycol in individuals also taking other medications at the time. This is not a reaction to the much smaller amounts found in food sources of propylene glycol.
Those with Allergic Reactions or Sensitivities
Propylene glycol was named Allergen of the Year in 2018 by the American Contact Dermatitis Society. As much as 3.5% of the population may have a skin allergy to the propylene glycol in cosmetic products, which results in skin irritation (dermatitis) and rash.
Those with sensitive skin may not want to use any products with propylene glycol, as studies have found that out of 38 people with sensitive skin given oral forms of the substance, 15 showed signs of rash within the next 16 hours. The same is true in cases of moisturizers and shampoos in which propylene glycol may act as an irritant.
How to Avoid Propylene Glycol Products
Though it's a safe product when found in low amounts in food, those with allergies or sensitivities may want to avoid propylene glycol as much as possible. If you want to make sure it's not in your food, look for "propylene glycol mono and diester" or E1520 (or 1520) on the food label, but also keep in mind that while products like frosting, dairy, and bread products may list it, other products using propylene glycol as a carrier may not.
As a general rule, avoiding processed junk and fast foods in favor of whole foods is your best bet, and if you do find you have an allergy to propylene glycol, make sure to alert your doctor before you're given injected medications.
Propylene Glycol in Processed Foods
The toxicity of propylene glycol is extremely low and has not been associated with causing any chronic conditions as a byproduct of use. In fact, the only instances of dangerous toxicity are found in extremely high doses like those given by health care professionals, such as in injections. Outside of that, those with sensitive skin may experience a mild allergic reaction to this food and cosmetic additive and may want to avoid what is otherwise a widely used and largely safe product.