What Does Comedogenic Mean?

Comedogenicity is the propensity for a cosmetic ingredient to clog your pores trapping bacteria within and leading to the formation of comedomes and pimples. People find it confusing and are seeking clarification on which plant-based oils are non comedogenic oils. It turns out that the answer is not so simple.

Some common questions:

Is olive oil non comedogenic? Yes, relatively so

Is jojoba oil non comedogenic? Yes, relatively so

Is argan oil non comedogenic? Yes, relatively so

Is castor oil non comedogenic? Yes, realtively so

One of the most commonly asked questions is: Is Coconut Oil non comedogenic? Generally, No, but liquid coconut oil may be less comedogenic than saturated coconut oil. And, coconut oil included in a product does not necessarily mean that the product itself will be comedogenic.

Factors That Affect The Comedogenic Nature Of Face Oils

Fatty Acid Profiles Of Plant-Based Oils

Plant oils are actually triglycerides in which the individual fatty acids that comprise the oils such as Linoleic acid, Linolenic acid, Oleic Acid, Palmitic Acid, Stearic Acid, Lauric Acid and Myristic Acid are linked together by glycerol molecules. Each oil has a unique fatty acid profile and composition.

Oils that are high in Linoleic Acid, Linolenic Acid and Oleic Acid tend to be non-comedogenic oils.

Oils that are high in Palmitic Acid, Stearic Acid and Myristic Acid tend to be more comedogenic oils.

But, the fatty acid profile is not the whole story of what makes a non comedogenic oil or a comedogenic oil.

Saturated And Unsaturated Plant-Based Oils

Oils also have different degrees of saturation. Oils that are unsaturated have many more free Carbon=Carbon double bonds in the triglyceride backbone than saturated, or hydrogenated, oils.

Saturated or hydrogenated oils have relatively few, if any, free Carbon=Carbon bonds in the triglyceride chain. The higher the degree of saturation, or hydrogenation, of an oil, the more viscous the oil becomes, even becoming solid at room temperature.

Unsaturated Plant Oils

Unsaturated oils tend to absorb quickly into the skin where saturated oils tend to sit on the surface of the skin and are slow to absorb. Most unsaturated oils are liquid at room temperture and tend to be relatively non-comedogenic oils.

Unsaturated, Non Comedogenic Oils for your face include Rosehip Oil, Sunflower Seed Oil, Squalane, Hemp Seed Oil, Grapeseed Oil, Jojoba Oil, Olive Oil, Argan Oil.

Saturated Plant Oils

Most highly saturated oils are actually solid at room temperture such as Coconut Oil and Babassu Oil and more resemble light butters such as Shea Butter and Mango Butter.

Comedogenic Oils

Oils that are comedogenic generally have high levels of Palmitic, Stearic, Lauric and Myristic Acids and are highly saturated or hydrogenated. This is a general rule, but there are exceptions.

Comedogenic Scale (Rankings): The Problem With The Comedogenic Scale

You’ve all seen the Comedogenicity Rankings of skincare ingredients scaling ingredients from 0 (non-comedogenic) to 5 (highly comedogenic). Most of these Comedogenicity Scales have been published for decades without changing. The problem with Comedogenicity Scale is that it is based on bad science.

How The Comedogenic Scales Were Determined

Rabbit Ear Model

In the 1970’s, a follicular dilation method was used to evaluate comedogenicity by using a rabbit ear model (REM). The methodology involved application of a cosmetic ingredient on a rabbit’s ear at concentrations of 10% to 100% and then evaluating the follicles of the rabbit ear to determine if the follicles were dilated, implying the dilation of the follicles was caused by the ingredient (hence, comedogenic) and the degree of dilation was indicative of the degree of comedogenicity.

The first problem with this approach to determining comedogenicity is the cosmetic ingredients were applied to the rabbit ear at high concentrations of 10% to 100%. This high level of exposure to an individual ingredient is rarely observed in cosmetic products. Further, ingredients are components of a cosmetic formula that contains several other ingredients and are rarely applied solo. Extrapolating an observation of the effect of an individual ingredient applied solo at high concentrations to the effect of that same ingredient at much lower concentration in a cosmetic formula containing several other ingredients is simply bad science. No direct correlation can be determined.

However, the main problem with the rabbit ear model is that while rabbit and human follicles have some similarities, rabbit skin has low physical and anatomical correlation to human facial skin. Human skin’s response to comedogenic ingredients is much slower than rabbit skin, is less likely to form comedomes, and has different sebaceous gland secretion activity. The REM is an ineffective and problematic method for determining comedogenicity in human skin.

Human Model For Assessing Comedogenicity

In the 1980’s a human model was used in which the test ingredients were applied to the upper part of the backs of young black males under occlusion (under a bandage) for up to one month. As with the Rabbit Ear Model, the ingredients were applied solo at high concentrations and/or neat.

More recent studies have been conducted by applying the ingredient to the upper back of males under occlusion for periods of 48 hours to 72 hours.

The flaws in this approach are that they use individual ingredients neat applied under occlusion on the upper back. This is a very flawed model for assessing comedogenicity in several respects: (1) The skin on the upper back of young males is not a good model for the general human population’s facial skin; (2) People apply cosmetic products on their face not their upper backs and do not generally apply individual ingredients neat, but as components of multi-ingredient products; (3) People do not apply cosmetic products to their face under occlusion (under a bandage) for 48 to 72 hours, much less without washing their face during that timeframe.

As with the Rabbit Ear Model, this is simply bad science.

Comedogenicity – Test The Product On Yourself

All individuals react differently to the application of cosmetic products. And, each and every cosmetic product contains different ingredients at different rates of inclusion and in different combinations. The only way to determine if a product is comedogenic on your skin is to actually use the product and see how your skin reacts to it. Generally, if the product is comedogenic on your skin, you will know within one week or so of use with the observation of comedomes.

Comedogenity And Acne-Prone Skin

For individuals struggling with acne-prone skin, your best approach is to not be overly concerned with the published comedogenicity ratings of individual ingredients and avoiding products containing those ingredients.

However, if you have concerns, avoid products that contain highly saturated oils that contain high amounts of Stearic, Palmitic, Myristic and Lauric Acids.

It is also advisable to avoid products that contain butters such as Shea, Mango and Cocoa Butter. But, even though a products contains ingredients such as Coconut Oil, Babassu Oil, Shea Butter, Mango Butter and Cocoa Butter, that product may not be comedogenic on your skin if these ingredients are included at relatively low percentages. You really need to patch test the product on your skin to see if it is comedogenic for you or not.

The true culprit is not so much individual cosmetic ingredients, but excess sebum production mixing with dead skin cells that form plugs in your hair follicles trapping the bacteria within the follicle. It’s genetic and hormonal in origin and most people age of out the acneic phase by their early 20’s.

Use relatively simple products such as a 2% Salicylic Acid solution that contain as few ingredients as possible. Salicylic Acid is oil soluble and will penetrate the hair follicles, mixing with the excess sebum and effectively act as a lubricant to prevent the shedding dead skin cells from forming plugs in the hair follicle leading to comedome formation. It also has anti-inflammatory and anti-microbial properties.

Other effective products for blemish-prone skin Vitamin C, Retinol, Lactic Acid, Glycerin, Hyaluronic Acid

For more reading on Comedogenicity here’s a great article on Byrdie.