What Is C18-70 Isoalkane?
C18-70 Isoalkane is a blend of branched hydrocarbons that contain between 18 and 70 carbon atoms. Although it comes from petroleum, it is heavily refined and purified, leaving a clear odorless liquid that feels silky rather than greasy. Chemists began using this ingredient in the late twentieth century as a lighter alternative to mineral oil. It was first listed as C18-70 Isoparaffin, but the name was updated to match current naming rules.
The manufacturing process starts with a selected petroleum fraction. Through distillation, hydrogenation and controlled isomerization, straight chains are converted into branched chains, which improves spreadability and skin feel. The result is a highly stable ingredient with very low impurities, making it suitable for leave-on skincare.
You will most often see C18-70 Isoalkane in moisturizers, barrier creams, face and body lotions, ointments, sunscreens, foundations, lip balms, cleansing balms, makeup removers and hair serums. Formulators like it for its lightweight finish and its ability to play well with both oils and silicones.
C18-70 Isoalkane’s Cosmetic Benefits/Uses
C18-70 Isoalkane serves mainly as an occlusive agent in topical products.
As an occlusive it forms a thin, breathable film on the skin or hair that slows down water loss. This helps keep skin hydrated longer, softens rough patches and can make formulas feel richer without adding heaviness. The film also gives products a smooth glide during application and can boost the durability of makeup by creating a flexible protective layer.
Who Can Use C18-70 Isoalkane
C18-70 Isoalkane suits most skin types. Dry and sensitive skin often benefit from its water-locking film while normal and combination skin appreciate the silky feel. Very oily or acne-prone skin can generally tolerate it thanks to its low weight but some individuals who react to any occlusive layer may prefer lighter humectants instead.
The ingredient is derived from petroleum, not animals, so it is acceptable for vegans and vegetarians when used in formulas that are otherwise free of animal-derived components.
No specific restrictions exist for pregnant or breastfeeding women when the ingredient is used topically at cosmetic levels. This is not medical advice and anyone who is pregnant or nursing should confirm with a doctor before starting a new product to be safe.
C18-70 Isoalkane does not cause photosensitivity and has no known interactions with sunscreens or common active ingredients. It is also fragrance-free and non-volatile which makes it suitable for people who avoid scented or alcohol-based cosmetics.
Potential Side Effects/Adverse Reactions
Side effects from topical C18-70 Isoalkane differ from person to person. The points below list potential reactions yet most users will not experience them when the ingredient is included correctly in a finished product.
- Mild skin irritation or redness in people highly sensitive to hydrocarbons
- Temporary clogged pores or breakouts in individuals prone to acne mechanica or folliculitis
- Greasy or heavy feel if applied in very large amounts
- Rare allergic contact dermatitis presenting as itching or rash
If a negative reaction occurs stop using the product and seek advice from a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1 / 5
C18-70 Isoalkane is highly purified and composed of large branched molecules that tend to sit on the skin surface instead of penetrating pores. Studies on similar isoalkanes and practical formulator feedback show a very low likelihood of clogging, which places it just above completely inert substances like squalane or mineral oil.
Most people prone to acne or breakouts can use products with this ingredient without problems, though extremely occlusion-sensitive individuals may still prefer lighter options.
Like any occlusive, its comedogenic impact depends on the overall formula and how thickly it is applied, so pairing it with heavy waxes or butters could raise the clogging potential of the finished product.
Summary
C18-70 Isoalkane acts mainly as an occlusive that locks in water, smooths rough areas and gives creams or makeup a silky glide. It achieves this by forming a thin flexible film of branched hydrocarbons that slows moisture loss while adding slip and spreadability.
While not as famous as silicones or classic mineral oil, it enjoys steady use in modern skincare and makeup because it mimics the cushioned feel of heavier oils without their greasy weight.
The ingredient is considered very safe: it is inert, fragrance-free, non-photosensitizing and rarely triggers irritation or allergies. As with any new cosmetic, patch test a small area first to make sure your skin agrees with the full formula.