Oily skin: which ingredients should be avoided?

Comedogenic ingredients, the number-one enemies of oily skin.

When you have oily or blemish-prone skin, it's not enough to control sebum production: you must also ensure that you don't trap it under a layer of occlusive ingredients. This is where the concept of comedogenicity. The term comes from the word “comedones” and refers to the ability of a cosmetic ingredient to block the pilosebaceous follicles, the structures into which the sebaceous glands produce sebum. When pores become clogged, sebum can no longer drain properly, promoting the development of blemishes. To assess this risk, we generally use the comedogenicity index, measured on a scale from 0 (non-comedogenic ingredient) to 5 (highly comedogenic ingredient).

This index depends in particular on the rate at which the ingredient penetrates the skin and its susceptibility to oxidation (some oils go rancid quickly, which can increase their comedogenic potential). In general, an ingredient rated 2 or lower is considered non-comedogenic and suitable for oily skin. However, those with an index above 3 are best avoided if you have oily skin, especially if you frequently experience blemishes. These ingredients include:

The animal waxes : beeswax (Beeswax), wool wax (Lanolin)...
Certain mineral oils and waxes derived from hydrocarbons, often used in foundation formulations: paraffin oil (Paraffinum Liquidum or Mineral Oil), paraffin wax (Cera Microcristallina), synthetic wax (Synthetic Wax), ceresine (Ceresin Wax)...
Certain vegetable oils and butters: wheat germ oil (Triticum Vulgare Germ Oil), coconut oil (Cocos Nucifera Oil), flaxseed oil (Linum Usitatissimum Seed Oil), rosehip oil (Rosa Canina Fruit Oil), soybean oil (Glycine Soja Oil)...
Some gums and resins: carrageenan (Carageenan), sodium alginate (Algin), xanthan gum (Xanthan Gum)...
Some fatty esters, in particular those derived from stearic acid (Stearic Acid), myristic (Myristic Acid) or palmitic (Palmitic Acid), as well as isopropyl myristate (Isopropyl myristate).

Note : The presence of comedogenic ingredients in a product does not necessarily lead to the appearance of blemishes, even on oily skin. It depends in particular on their concentration in the formula, the other components, and the inherent reactivity of each individual’s skin. Identifying them is a useful guideline, but on its own it is not enough to predict a product’s tolerance.

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Active ingredients that are excessively cleansing or drying should be avoided.

When faced with oily skin, there’s a strong temptation to use harsh, stripping treatments for a healthier feel. However, this relief is misleading: overly aggressive surfactants or drying agents don’t fix the problem; they exacerbate it in the medium and long term. Indeed, when the skin is deprived of its hydrolipidic film, it interprets this as an assault. It then activates a defense mechanism: reactive hyperseborrhea. The sebaceous glands increase their activity to compensate for this loss and restore the skin’s natural barrier. Thus, rather than becoming less oily, the skin produces even more sebum, resulting in a rebound effect. This overproduction can also cause dysbiosis, i.e., an alteration of the skin microbiota, by promoting the proliferation of the bacterium Cutibacterium acnes. The ingredients most frequently implicated are:

The high-proof alcohols: SD 40 alcohol, denatured alcohol, ethanol, isopropyl alcohol.
Some sulfated surfactants : sodium lauryl sulfate (SLS), sodium laureth sulfate (SLES).

These detergent actives can disrupt the skin’s barrier function, reducing its capacity to retain water and increasing its permeability to irritants. A recent study on 47 volunteers with oily yet sensitive skin—which, contrary to some assumptions, is entirely feasible—revealed that this skin profile exhibits compromised epidermal barrier integrity, characterized by increased water loss, altered lipid composition, and heightened sensitivity to irritants. Metabolomic analyses uncovered disruptions in sphingolipid and amino acid metabolism, key molecules in maintaining cutaneous integrity. Specifically, 48 essential metabolites, including several types of ceramides, were decreased, while 15 others showed increased abundance, indicating persistent cutaneous stress.

Key takeaway : Regular use of drying or detergent-based active ingredients makes the skin more reactive and dehydrated, even when it’s oily. Reactive hyperseborrhea may then develop, creating a vicious cycle that is difficult to break.

The excessively abrasive particles in certain scrubs must be completely avoided.

The physical exfoliants, or mechanical scrubs, rely on manual friction to remove dead skin cells. This process, although sometimes effective in smoothing the skin, can become problematic when applied to already weakened skin, particularly by acne. By exerting an abrasive action, these scrubs can irritate the epidermis, cause microlesions, and exacerbate preexisting inflammation. If the particles are large or have irregular edges, the risk of damaging the skin barrier is even higher.

Particle size plays a central role: micro-grains can be well tolerated by oily skin.

On the other hand, larger particles may become problematic in the presence of acne lesions. When they pass over an inflamed or healing pimple, they may rupture the pustule wall, promoting the spread of bacterial contents, particularly of Cutibacterium acnes, to adjacent areas. This phenomenon increases the risk of new lesion formation and prolongs inflammation. Scrubs with particle sizes that should be monitored include:

Fruit kernels: apricot kernels (Prunus Armeniaca Seed Powder), peach kernels (Prunus Persica Seed Powder), plum kernels (Prunus Domestica Seed Powder), walnut shells (Juglans Regia Shell Powder) or hazelnut shells (Corylus Avellana Shell Powder).
Abrasive synthetic particles : polyethylene microbeads (Polyethylene), polypropylene (Polypropylene) or certain PEG/PPG-type polymers (Polyethylene Glycol, Polypropylene Glycol), increasingly less used today but still present in some products.
Very hard exfoliating crystals : raw brown sugar (Sucrose), unrefined coarse sea salt (Sea Salt).

For oily, blemish-prone skin, it is best to use chemical exfoliants, which act without direct abrasion. Beta-hydroxy acids (BHAs), particularly salicylic acid, are the most suitable. Lipid-soluble, it penetrates into pores and dissolves the sebum and keratin build-up that leads to comedones. Moreover, beyond its keratolytic activity, salicylic acid exhibits antibacterial effects on Cutibacterium acnes. This active compound can therefore be considered a valuable ally for oily skin.