Propylene Glycol in Food: Why It’s on the MRT Panel and Where It’s Hiding

Kerry Watson, NTP, RWP
Nutritional Therapy Practitioner & Restorative Wellness Practitioner • Evidence-based food sensitivity guidance

Propylene glycol is the exact same chemical class used in antifreeze. It is also hiding in your salad dressing, your ice cream, and your daily vitamins. The FDA says it is safe. Your MRT panel says your white blood cells disagree.

What Is Propylene Glycol?

Propylene glycol (PG) is a synthetic liquid substance that absorbs water. The FDA classifies it as a “generally recognized as safe” (GRAS) food additive. Food manufacturers use it as a solvent, a humectant, an emulsifier, and a preservative. It keeps baked goods moist and prevents ice crystal formation in frozen foods.

It is also used as a carrier for flavorings and food colors. But where else do you find this chemical? You find the same chemical in antifreeze, e-cigarettes, pharmaceutical preparations, and cosmetics. Most people are shocked when they learn they are eating it every single day.

Why It’s on the MRT 176 Panel

All disease starts in the gut. The MRT test specifically includes propylene glycol as a chemical antigen because it triggers mediator release in sensitive individuals. When your immune cells encounter PG, they release histamine, cytokines, and prostaglandins. This creates a delayed immune response, not an IgE allergy. Reactions take 24 to 72 hours to appear.

When these inflammatory mediators flood your system, you get in to trouble. Symptoms include severe migraines, skin reactions like eczema flares and rashes, intense GI distress, brain fog, and debilitating joint pain. Because this chemical is in so many food products and medications, clients who react to PG often cannot figure out why they keep having symptoms even when they think they are eating clean.

Where Propylene Glycol Hides

You will find propylene glycol in salad dressings and marinades because it keeps the ingredients mixed. You find it in ice cream and frozen desserts. It is in flavored coffees and drink mixes. It is heavily used in cake mixes and baked goods as a humectant to retain moisture.

It is a standard carrier solvent for food colorings. If a product has artificial color, PG is present. It is also used in “natural flavors” as a carrier for flavor extracts. Medications use it too. Soft gel capsules and liquid medications often have gel shells made with PG. Most liquid vitamin supplements rely on it. Even pure vanilla extract uses it as a common solvent.

The Label-Reading Problem

The real problem with propylene glycol is that it does not always appear by name on food labels. When manufacturers use it as a processing aid or carrier for flavors and colors, FDA rules exempt it from labeling requirements. You eat it without ever seeing it on the ingredient list.

When it is listed, it appears under different names. You will see it called propane-1,2-diol, E1520, methyl glycol, or trimethyl glycol. This is exactly why generic elimination diets fail for PG-sensitive clients. You cannot eliminate what you cannot identify on a label. The MRT test is a big deal because it catches this sensitivity by testing your blood directly against the chemical. Your blood knows what you are reacting to, even if the label hides it.

The Connection to Artificial Colors

From our recent analysis of 20,683 grocery products, we found FD&C synthetic dyes in 6,633 products. The majority of those dyes use propylene glycol as their carrier solvent. This means your PG exposure is far higher than any ingredient list suggests.

We also saw polysorbate 80, another emulsifier on the MRT panel, in 141 products. PG and polysorbate 80 often appear together in highly processed foods. Our data showed citric acid in 38.4% of products. We also found glycerin, or glycerol, in 1,110 products. Glycerin is related to propylene glycol but they are completely different chemicals tested separately on your MRT panel.

What to Do During Your LEAP Protocol

During LEAP Phase 1, all PG is removed by default. You are eating single-ingredient whole foods. The challenge hits in Phase 2 and Phase 3 when you start reintroducing packaged foods. Foods that appear clean on the label contain PG as a hidden carrier.

You need to check all medications and supplements with your practitioner. Many clients react during LEAP not because of the food they eat, but because their daily supplements contain PG in the capsule or as a filler. When you are in doubt, you must contact the manufacturer directly and ask them if propylene glycol is used as a processing aid.