1. Skin Irritation and Allergic Reactions
One typical adverse reaction to propylene glycol includes mild skin irritation. Usually, this happens in people who are allergic to the chemical and subsides after a short period of time after the body has had time to break down the compound. (5)
If exposed to the eyes, propylene glycol can cause mild conjunctivitis.
2. Potentially Toxic to the Kidneys and Liver
Propylene glycol is used in many IV medications, including Lorazepam, an anxiety-reducing and seizure treatment medication. This drug is often administered to patients with extensive burns as sedation during the healing process or to psychiatric patients. When given Lorazepam for an extended period of time in large doses, clinicians have discovered possible kidney issues in the form of increased creatinine levels in the blood. (6) Generally, creatinine (a product of muscle breakdown and growth) remains in consistent levels in the bloodstream. Excess creatinine is a sign that the kidney is unable to process compounds at a normal rate.
People who already operate with poor kidney function are unlikely to be able to process propylene glycol efficiently and should avoid exposure when possible.
A 2007 study from the University of Connecticut assessed the treatment of propylene glycol toxicity and also noted it can be dangerous for those with liver problems. (7)
On an interesting, positive note, propylene glycol might actually have the ability to protect your liver from damage done by the common headache medication, acetaminophen. (8)
3. Probably Not Safe for Infants or Pregnant Women
Prospective mothers are usually very cautious during and after pregnancy to ensure their children’s health. In the case of propylene glycol, it should be no different.
While some research states that neonates (preterm infants) have been found to have no adverse side effects from propylene glycol, it’s also true that infants cannot break down this compound as quickly as an adult can. (9, 10) This is due to the enzyme pathways that are still in development at the time of birth — depending on whom you ask, the period of development can last anywhere from six months to four years.
Before the completed growth of these enzyme pathways, parents should avoid allowing their children to ingest or be exposed to many chemicals that are potentially harmful, and pregnant mothers should do the same. (11)
4. Neurological Symptoms
The one area in which the CDC’s toxicity profile negatively assessed propylene glycol was in the area of neurological symptoms. When taken orally and tested by patch test to find the amount of the chemical still in their system, a number of people were found to have varying degrees of neurological issues, including stupor, convulsions and other unspecified “severe mental symptoms.”
In a cat-based study, cats receiving the high dose developed “decreased activity, mental depression, and slight to moderate ataxia.”
It’s important here to note that the humans in the noted studies above had been exposed to orally administered medication containing propylene glycol and were most likely allergic to it.
5. Cardiovascular Problems
Heart disease and symptoms have been commonly associated with propylene glycol exposure, mostly in part due to a few case studies that have caused alarming concern. One such patient was an 8-month-old who suffered a heart attack after four doses of topical medication to treat a burn.
A horse was also reported to suffer a myocardial edema after a mistaken oral dosage of a very large amount of propylene glycol.
6. Respiratory Issues
There are conflicting reports regarding the impact of inhaled propylene glycol. As it’s a fairly common ingredient in smoke machines (for theater productions) and other inhalable substances, this is an important distinction to make. In rats, some scientists have found enlarged cells in the respiratory tract, as well as some nasal hemorrhaging. In another case, the horse mentioned above who suffered myocardial edema eventually died of respiratory arrest.
While the conditions under which these studies occurred are unlikely to be repeated in humans, this information is still relevant. Many substances can be potentially toxic in massive doses, and it’s impossible to guarantee these chemicals do not build up in dangerous levels, especially in some cases.
7. Potentially Bioaccumulative in Certain Cases
I did mention earlier that propylene glycol is not considered bioaccumulative (builds up over time in the bloodstream). However, critically ill adults may be an exception to this rule. When administered large doses of Lorazepam, adults with or without kidney issues have experienced an abnormal buildup of propylene glycol. (12)
If you suffer from kidney or liver issues that may affect your body’s ability to process organic compounds, or are chronically ill, I highly recommend limiting your exposure to this compound as much as possible.
One interesting case study followed a 24-year-old woman diagnosed with pneumonia. She was given Lorazepam for 18 days to treat her severe respiratory distress, at which time she developed lactic acidosis, a condition marked by lowering the body’s pH level to a dangerous extreme. After discontinuing the drug that poisoned her body, her condition stabilized for a period of time, but she later died after her condition deteriorated again. (13) Again, this is an example of the rare (but possible) effects of the accumulation of propylene glycol in your system.
8. May Be a Pathway for More Harmful Chemicals
Perhaps the most concerning part of constant propylene glycol exposure is the way that it may provide other chemicals a free pass into your bloodstream. Propylene glycol increases your skin’s propensity to absorb whatever it comes into contact with. Considering the large amount of dangerous chemicals we encounter on a regular basis, this may be of even more danger than the compound itself.