Is Propylene Glycol in Milk?

Today I continue my investigation of whether propylene glycol could be present in foods to which I previously thought I had an intolerance. I’ve been intolerant of dairy for about 10 years now, experiencing extreme intestinal distress. That distress, gassiness, and discomfort are some of the symptoms I experience from eating propylene glycol. Could I have been experiencing propylene glycol allergy symptoms all along?

  1. While it is not a universal procedure, it is common to include propylene glycol in dairy cow feed, either as a maintenance diet or as a treatment for ketosis. Ketosis is caused by over-milking cows, causing them to lose more body fat than they should for milk production. The resulting weight loss causes release of chemicals (specifically, ketones) from fatty tissues in the cow’s body at much higher concentrations than can safely be maintained by the body, causing illness. These ketones also get into the milk supply, making it less safe for human consumption. Adding propylene glycol to the feed helps cows to maintain or increase milk production without losing as much body fat, just as it does with egg-laying chickens. The¬†resulting milk is lower in fat. It also has reduced ketone content (as intended).
  2. Propylene glycol, as in chickens, should be entirely metabolized by the cow (chemically changed into other things) within a few hours, and thus should not end up being stored in muscle tissue, but could be excreted by the animal.
  3. Propylene glycol is also present in medicated balm applied to the udders of dairy cows to prevent mastitis (painful swelling of the tissue due to blockage). It is said that this balm is only effective if the chemicals penetrate through to the milk. This treatment could be applied only as needed, or as a maintenance procedure to prevent mastitis from occurring in the first place. London Dairy Supply, a dairy industry supplier, does not appear to sell anything like this. Instead, they use chemicals containing glycerin (possible cross-reactor for PG) that are applied through dipping or spraying the teat. This seems more reasonable for commercial dairy producers, as it is a lot faster.
  4. Propylene glycol is found in a number of cheese starter cultures/rennet, if not as an ingredient in itself, then as a part of added colour. It is also found as an emulsifier and stabilizer in ice milk products, ice cream, and frozen yogurt. I was unable to learn if propylene glycol was added to yogurt in any other way than as a flavour and colour ingredient, but it is allowed to be added to cream cheese. Other dairy-based products could contain added propylene glycol for similar reasons.

Based on the above, it is possible that fat in the milk is partially replaced by propylene glycol, and that propylene glycol and/or glycerin would be in the milk of cows treated for mastitis. This would mean that any milk-based product made with that milk would contain propylene glycol or glycerin as well, before the above additives are added. Unfortunately, I can find no chemical analysis of milk searching for this chemical in the milk. It simply does not appear to have been studied, and so I cannot confirm or reject my theory in this way. As with the possibility of chemical contamination of eggs, I hope to test this theory when I can find a source of dairy that could not possibly be contaminated with propylene glycol.

Do you show allergic symptoms to consuming propylene glycol and also an intolerance to dairy? Comment below.

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