Oily skin: which ingredients should you avoid?

Comedogenic ingredients: oily skin’s number-one enemies.

When the skin is oily or prone to imperfections, simply controlling sebum production is not sufficient: one must also ensure it is not trapped beneath a layer of occlusive ingredients. This is where the concept of comedogenicity. This term derives from the word 'comedones' and denotes the capacity of a cosmetic ingredient to obstruct the pilosebaceous follicles, the organs onto which the sebaceous glands that produce sebum. When the pores are blocked, sebum can no longer be discharged properly, which promotes the appearance of imperfections. To assess this risk, the comedogenicity index is generally used, calculated on a scale from 0 (non-comedogenic active) to 5 (highly comedogenic active).

This index depends in particular on the rate at which the ingredient penetrates the skin and on its susceptibility to oxidation (some fatty substances turn rancid quickly, which can increase their comedogenic potential). Generally, an ingredient rated 2 or below is considered non-comedogenic and suitable for oily skin. Conversely, those with an index above 3 should be avoided if you have oily skin, especially if you are frequently prone to blemishes. These include the following ingredients:

The animal waxes : beeswax (Beeswax), wool wax (Lanolin)...
Some mineral oils and waxes derived from hydrocarbons, often found in foundations: paraffin oil (Paraffinum Liquidum or Mineral Oil), paraffin wax (Cera Microcristallina), synthetic wax (Synthetic Wax), ceresine (Ceresin Wax)...
Some 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), or isopropyl myristate (Isopropyl myristate).

Note : The presence of comedogenic ingredients in a product does not systematically lead to the appearance of blemishes, even on oily skin. It depends in particular on their concentration in the formula, on the other ingredients and on the intrinsic reactivity of each individual’s skin. Identifying them is a useful reference point but, on its own, is not sufficient to predict a product’s tolerability.

Actives that are excessively cleansing or drying should be avoided.

When faced with oily skin, there is a strong temptation to use treatments that “strip” it for a healthier sensation. Yet this relief is deceptive: overly harsh or drying actives do not resolve the problem; they worsen it in the medium and long term. Indeed, when the skin is deprived of its hydrolipidic film, it perceives this as an assault. It then activates a defence mechanism: reactive hyperseborrhoea. The sebaceous glands increase their activity to compensate for this loss and restore the skin’s natural protection. As a result, instead of becoming less oily, the skin produces even more sebum, creating a rebound effect. This overproduction can also lead to dysbiosis, that is an alteration of the cutaneous microbiota, by favouring the proliferation of the bacterium Cutibacterium acnes. The ingredients most frequently implicated are:

The strong alcohols: SD 40 alcohol, denatured alcohol, ethanol, isopropyl alcohol.
Some sulphated surfactants : sodium lauryl sulphate (SLS), sodium laureth sulphate (SLES).

These detergent agents can disrupt the skin’s barrier function, reducing its ability to retain water and increasing its permeability to irritants. A recent study involving 47 volunteers with oily yet sensitive skin—which, contrary to popular belief, is entirely possible—demonstrated that this skin profile exhibits an impaired epidermal barrier, characterised by increased water loss, altered lipid composition and heightened sensitivity to irritants. Metabolomic analyses revealed disturbances in sphingolipid and amino acid metabolism, key molecules in maintaining skin integrity. Specifically, 48 essential metabolites, including several types of ceramides, were decreased, while 15 others showed increased abundance, indicating persistent skin stress.

Key takeaway : Regular use of drying or detergent actives makes the skin more reactive and more dehydrated, even if it is oily. Reactive hyperseborrhoea may then occur, creating a vicious circle that is hard to break.

Particles that are too abrasive in certain scrubs must be avoided entirely.

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

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

However, larger particles can become problematic in the presence of acne lesions. When they pass over an inflamed or healing blemish, they may rupture the pustule wall, facilitating the dispersal of bacterial contents, particularly from Cutibacterium acnes, into neighbouring areas. This phenomenon increases the risk of new lesions developing and prolongs inflammation. Scrubs with particle sizes to 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).
Synthetic abrasive particles : polyethylene microbeads (Polyethylene), polypropylene (Polypropylene) or certain PEG/PPG-type polymers (Polyethylene Glycol, Polypropylene Glycol), now increasingly phased out but still present in some products.
The very hard exfoliating crystals : unrefined raw brown sugar (Sucrose), coarse unrefined sea salt (Sea Salt).

For oily, blemish-prone skin, it is best to opt for chemical exfoliants, which act without direct abrasion. Beta-hydroxy acids (BHAs), in particular the salicylic acid, are the most suitable. Being oil-soluble, it penetrates the pores and dissolves the sebum and keratin plugs responsible for comedones. Furthermore, in addition to its keratolytic action, salicylic acid exerts an antibacterial effect onCutibacterium acnes. This active ingredient can thus be considered an ally for oily skin.