Sexy Little Things

All girls love perfume. This is one of our favourites, Victoria's Secret, Heartbreaker.
Got interested in what does it contain while using it one morning, and guess what we found in this?
It actually contain propylene glycol!
Did a brief research on it and found out that there are people who are allergy to Propylene Glycol.
Hence, we decided to find out an effective way to detect the presence of Propylene Glycol in Cosmetic Products.

Propylene Glycol

Melting Point: -59°C

Density: 1.04g/cm³

Formula: C3H8O2
Boiling point: 188.2°C
Molar mass: 76.09 g/mol

IUPAC ID: Propane-1,2-diol

What is Propylene Glycol?

Propylene glycol (also known as 1,2-propanediol or propane-1,2-diol) is an organic compound. It is a colorless, nearly odorless liquid that is miscible with acetone, water and chloroform. Propylene glycol molecule itself is chemically inert (not chemically reactive), and because of this special feature propylene glycol becomes an idealistic compound when seeking to combine contrasting chemical elements to form a single, homogenous fluid. It act as an emulsifier that connects and stabilizes active ingredients that is insoluble with one another (would not mix) and create a stable homogenous fluids that will allow the intended final project. This inert feature of propylene glycol also allows it to develop an ability to attract water/moisture. Hence, propylene glycol is one of the most widely used ingredients in cosmetic product as it can help to hold and dissolves active ingredients equally in a medium (e.g. perfume, shower foam, lipstick) and act as a moisturizer in cosmetic formulas (e.g. facial cream, toner)

Some examples of the cosmetic products that contain propylene glycol are…

Personal care: Facial Cleanser, Shaving Foams, Lipsticks, Perfumes, Antiperspirant deodorants

Skin Care: Hand, Body and Facial Moisturizer, sunscreen products

Hair Care: Styling Gels, Shampoo, Conditioners

Oral Care: Mouthwashes, toothpaste

Baby care: Baby wipes, antiseptics

So is propylene glycol safe??

Propylene glycol can enter the bloodstream by inhaling air containing mists or vapors from this compound or through skin via direct contact with it. Consumption of propylene glycol can also be a way for the compound to enter the bloodstream. Propylene glycol will be broken down by the body within 48hours.

According to the FDA (Food and Drug Administration), Propylene glycol is GRAS (generally recognized as safe). Base on the results of human irritation and sensitization test, it the CIR Expert panel concluded that Propylene Glycol is safe to be used in cosmetic products at concentration up to 50%.  However, it was also noted that patients with diseased skin (e.g. eczema) may be susceptible to developing irritation/sensitization reaction to Propylene Glycol.

In 2003, the National Toxicology Program’s Centre for the Evaluation of Risk to Human Reproduction (CERHR) Expert Panel reviewed the reproductive and developmental effect of Propylene Glycol and concluded that there is “negligible concern for reproductive or developmental toxicity to humans.” 
Studies were also conducted on dogs and rats, which were fed doses of PG ranging from 2 to 5 grams per kg of body weight per day. The results showed that there is no links of Propylene Glycol to cancer. Hence, Cosmetic Ingredient Review Expert Panel concluded that there was no carcinogenic risk with low levels of ingestion of PG.

So what is the big fuss about PG found in cosmetic products all about??

A study was conducted by a dermatologist from the North American Contact Dermatitis Group (NACDG) and the results shown that repeated exposures to propylene glycol for a short time may cause irritation and allergies. Using the database, they analyzed the number of products containing allergens. According to Table 1, Propylene glycol is found to be the second most commonly present allergen in deodorants and antiperspirants. It is found in 47% of the deodorants and antiperspirants of the database, at a concentration of 2 to 5% of the product weight. This low concentration of propylene glycol is unable to elicit the irritation for patients with Propylene glycol allergy. However, it is recommended to avoid deodorant and antiperspirant with Propylene Glycol, as exposure over time may change the elicitation threshold, and thus causing dermatitis.

Though cancer might not be a concern (according to the Cosmetic Ingredient Review Expert Panel), it was found that Propylene Glycol can provoked allergic reactions in patients with eczema and other skin allergies, even in formulations of much less than 50%.

In addition, the Material Safety Data Sheet (MSDS) cites skin, liver and kidney damage that can result from contact with PG, and it gives safe handling instructions, calling it a hazardous substance. Though not specified, this is for the more concentrated industrial grade.

On the other hand, studies done in vitro tests on mammalian cells revealed that some cells underwent mutation when contact repeatedly with PG.
In Europe, where the authorities are much more cautious about what is allowable in cosmetics and foods, propylene glycol is limited to mostly non-food uses. 

Method to detect Propylene Glycol in Cosmetic

A wide range of ingredients in found in Cosmetic, for example, in a simple Victoria secret perfume, the ingredients found are...

Since propylene glycol is a liquid, Gas Chromatography-Mass Spectrometry is one of the method to detect propylene glycol. Analyte: Propylene Glycol

Gas Chromatography-Mass Spectrometry

An analytical method that combine features of gas-liquid chromatography and mass spectrometry to identity different known substances within a test sample and identify trace elements in materials that were previously thought to have disintegrated beyond identification.

High-Performance Liquid Chromatography (HPLC)

A technique in analytic chemistry used to separate the components in a mixture to identify and quantify each component.  It relies on pumps to pass a pressurized liquid solvent containing the sample mixture through a column filled with a solid absorbent material. Each component in the sample would then interacts slightly differently with the adsorbent material, causing different flow rates for the different components and hence leading to the separation of the components as they elute out the column.