Are vegetable oils comedogenic?

A comedogenic plant oil is an oil likely to trigger comedone formation.

This is an important factor to check before using a plant oil for combination to oily skin. Comedogenic plant oils have a greasy texture and can form a semi-occlusive film on the skin surface. While this film prevents transepidermal water loss, it can also block normal sebum release by blocking the skin’s pores, which leads to the formation of blackheads or whiteheads. Not all plant oils share the same comedogenic potential. Several factors affect their pore-clogging potential, including:

• Oxidation sensitivity and freshness of vegetable oil.

  Some plant oils are more sensitive to oxidation than others. Oils rich in antioxidants and containing a majority of saturated fatty acids—that is, without double bonds that react with oxidants—are more stable than oils low in antioxidants and containing a high proportion of unsaturated fatty acids. When a plant oil oxidizes, its organoleptic properties change : it tends to thicken and become more comedogenic. Several factors can cause this oxidation, including exposure to oxygen, light, heat, or container interactions.

• The quality of plant oil.

  A plant oil obtained by cold-press extraction has lower comedogenic potential. This process avoids chemical treatment and exposure to high temperatures that can degrade fatty acids and form compounds that may not benefit the skin.

• Vegetable oil penetration rate in the epidermis.

  Thick, greasy plant oils are poorly absorbed by skin, increasing their occlusive nature. Conversely, the greater an oil’s affinity for skin, the more easily it penetrates. These oils are termed dry and consist mainly of omega-3s, such as alpha-linolenic acid, and omega-6s, like linoleic acid. Fatty oils contain more omega-9s, such as oleic acid.

Each plant oil has a comedogenicity index determined by analyzing its freshness, oxidation level, and skin absorption rate.

The comedogenicity of vegetable oils is traditionally measured on a scale from 0 to 5.

• Index 0: It indicates the plant oil is non-comedogenic and suitable for combination or oily skin prone to blemishes. These oils include argan oil, hemp oil, prickly pear seed oil, jojoba oil, and hazelnut oil.

• Comedogenic rating 1 to 2: This category includes low-comedogenic oils, among them the sweet almond oil, the apricot kernel oil, the castor oil or the black seed oil.

• Comedogenicity ratings 3 and 4: Oils with a comedogenicity rating of 3 or 4 clog pores. This includes coconut oil, flaxseed oil, rosehip oil and soybean oil.

• Comedogenic rating 5: A vegetable oil with a rating of 5 has strong comedogenic potential, such as wheat germ oil.

Combination-to-oily skin should use vegetable oils with a comedogenic index of 0 to 2, while normal-to-dry skin can use oils with indices of 0 to 5. Contrary to common belief, blemish-prone skin does not have to avoid vegetable oils: they should choose the most suitable ones. Note that the presence of a comedogenic vegetable oil in a product does not cause breakouts in every case. Its concentration, the formula’s delivery system, synergy with other ingredients, and the user’s skin type are factors to consider.

It can be difficult to know if a plant oil is comedogenic based on texture alone. If in doubt, we advise consulting the table below, listing the main plant oils used in skincare and their comedogenicity index.

• FULTON J. E. Comedogenicity and irritancy of commonly used ingredients in skin care products. Journal of the Society of Cosmetic Chemists (1989).

• DINARDO J. C. & al. A re-evaluation of the comedogenicity concept. Journal of the American Academy of Dermatology (2006).

• SHOJAN A. & al. Comedogenicity of oils. International Journal of Contemporary Medical Research (2019).