What Is C15-18 Glycol?
C15-18 Glycol is part of a family of ingredients known as glycols, which are small alcohol molecules that carry two hydroxyl groups. The numbers in its name refer to the length of the carbon chain, meaning it is a blend of 15 to 18-carbon diols. This chain length makes it more nourishing and less sticky than the lighter glycols you might see on labels, such as propylene glycol.
The ingredient is most often derived from plant oils rich in longer fatty acids, like coconut or palm. Through a controlled hydrogenation and oxidation process, those fatty acids are converted into the diol structure that gives C15-18 Glycol its skin-friendly traits. First introduced in the 1990s, it gained traction as brands looked for multifunctional ingredients that could moisturize while also boosting the stability of creamy formulas.
You will mainly spot C15-18 Glycol in products that aim to feel silky and cushiony on the skin. Think daily moisturizers, night creams, richer sheet mask essences, leave-on face masks, and targeted anti-aging treatments that need extra body and a smooth glide. It is also used in makeup like cream foundations or stick blushes where a soft, non-greasy finish is key.
C15-18 Glycol’s Cosmetic Benefits/Uses
C15-18 Glycol offers several perks that make it a valuable multitasker in modern skincare and makeup.
- Emulsion stabilising – Helps water and oil stay evenly blended so the product keeps a uniform texture from the first use to the last, preventing separation in creams and lotions
- Skin conditioning – Adds a light moisturizing layer that leaves skin feeling soft and supple without a heavy or greasy residue
- Emollient – Smooths and fills in tiny surface gaps, improving the overall feel of the product and giving skin a velvety finish
Who Can Use C15-18 Glycol
C15-18 Glycol is generally friendly to most skin types. Its emollient nature makes it especially comforting for normal, dry and mature skin that craves extra softness. Combination and mildly oily skin usually tolerate it well because it feels light rather than greasy. Those with very oily or highly acne-prone skin should monitor how their complexion responds, as richer textures can sometimes feel too occlusive for them.
The ingredient is sourced almost exclusively from plant oils so products formulated with it are typically suitable for vegans and vegetarians. If animal-derived feedstocks were ever used the brand would need to state that, but such sourcing is uncommon.
C15-18 Glycol has no known issues for women who are pregnant or breastfeeding when used topically in cosmetics. This is not medical advice and anyone who is expecting or nursing should ask a healthcare professional before adding new products to their routine.
Unlike some actives it does not increase the skin’s sensitivity to sunlight, so there is no added risk of photosensitivity.
Potential Side Effects/Adverse Reactions
Responses to topical C15-18 Glycol vary from person to person. The effects listed below are only potential outcomes and most users will not experience them when the ingredient is used correctly in a finished formula.
- Mild skin irritation such as temporary redness or stinging, usually in very sensitive individuals
- Contact dermatitis in those with a specific allergy to glycols
- Occasional clogged pores or breakouts on skin already prone to congestion if the overall product is very rich
- Exacerbation of existing dermatitis or eczema when used on compromised skin barriers
If any unwanted reaction occurs stop using the product and seek advice from a qualified medical professional.
Comedogenic Rating
Rating: 2/5
C15-18 Glycol sits on the low end of the scale because its long carbon chain makes it more occlusive than light glycols, yet it is still a diol that absorbs without leaving a thick film. Most users will not see clogged pores, but very oily or highly congested skin could notice a slight increase in surface buildup if the overall formula is rich.
Generally suitable for acne-prone skin, though those who break out easily may prefer lighter textures or lower usage levels.
Formulas that pair it with heavier butters or waxes can raise the pore-clogging potential, so the full ingredient list matters as much as this single component.
Summary
C15-18 Glycol acts as an emulsion stabiliser, skin conditioner and emollient. Its dual hydroxyl groups attract a hint of water while the 15-18 carbon backbone delivers a silky cushion that glides over skin, preventing phase separation in creams and leaving a soft velvety finish.
It is a steady performer rather than a headline-grabbing star, showing up most often in moisturisers, masks and stick makeup where smooth spreadability is prized.
Safety data and real-world use point to a low risk profile with rare irritation reports. As with any new cosmetic, patch testing is a smart step when trying products that contain C15-18 Glycol.