What Is Bis-C30-45 Alkyl Dimethicone?
Bis-C30-45 Alkyl Dimethicone is a specialty silicone made by joining a traditional dimethicone backbone with very long chain hydrocarbons that contain between 30 and 45 carbon atoms. The result is a large, oil soluble molecule that combines the smooth glide of silicone with the cushy feel of a lightweight oil. Like most cosmetic silicones it is man-made, starting with silica that is turned into siloxane units, then reacted with long chain alkyl groups in a controlled process called hydrosilylation. This step locks the big hydrocarbon tails onto the dimethicone, giving the polymer its unique texture and staying power.
Silicones began appearing in beauty products in the 1950s, first for their silky slip and water repelling traits. Formulators later looked for ways to boost richness without heaviness, which led to high molecular weight hybrids such as Bis-C30-45 Alkyl Dimethicone. Because it is too large to evaporate it leaves a soft, flexible film on skin or hair.
You will most often find it in silky moisturizers, nourishing face oils, makeup primers, liquid foundations, long wear sunscreens, hair smoothing serums, wash-off masks and anti aging night creams. It is prized when a formula needs lasting softness without greasy afterfeel.
Bis-C30-45 Alkyl Dimethicone’s Cosmetic Benefits/Uses
This ingredient is chosen for two main jobs in beauty formulas
- Skin conditioning: The large silicone film cushions the skin surface, improving softness and helping rough spots feel smoother. It also enhances spreadability so products glide on easily and sit evenly
- Emollient: The long alkyl chains mimic natural skin oils, filling tiny surface gaps and locking in moisture. This gives a supple, nonsticky finish that can reduce the look of dry lines
Who Can Use Bis-C30-45 Alkyl Dimethicone
Because this silicone sits on top of the skin rather than soaking deep inside it generally suits dry, normal and combination complexions that want a silky finish without greasy weight. Oily or acne prone skin can usually tolerate it as well since the molecule is too large to sink into pores, though a small number of users who react poorly to any occlusive film might prefer lighter textures. Sensitive skin often appreciates its cushioning barrier that helps cut down on friction.
Bis-C30-45 Alkyl Dimethicone is fully synthetic and contains no animal derived raw materials so it is suitable for vegans and vegetarians.
The ingredient is considered low risk for pregnancy and breastfeeding. That said this is not medical advice and anyone who is pregnant or nursing should review new skincare products with a qualified doctor to be extra sure.
It does not cause photosensitivity and will not make the skin more reactive to sunlight. There are also no known ingredient conflicts so it layers well with most actives, pigments and sunscreens.
Potential Side Effects/Adverse Reactions
Responses to topical Bis-C30-45 Alkyl Dimethicone differ from person to person. The effects listed below are simply potential outcomes and are unlikely for most people when the ingredient is used in a properly formulated product.
- Mild pore congestion or breakouts in individuals who are highly prone to occlusive films
- Temporary skin irritation such as slight redness or itch if the user is sensitive to silicones
- Rare allergic contact dermatitis presenting as swelling or a rash
- Pilling when layered over certain water rich serums which can lead to product flaking off the skin
If any unwanted reaction develops stop using the product and consult a healthcare professional if symptoms persist or worsen.
Comedogenic Rating
Rating: 1 (low likelihood of clogging pores). The molecule is very large and sits on the surface rather than slipping into follicles, so it rarely blocks pores. It does create a breathable film that can trap existing sebum or debris if the rest of the formula is heavy which is why the rating is not a perfect zero.
Most people who are prone to acne or breakouts can use products containing Bis-C30-45 Alkyl Dimethicone without trouble.
Because it repels water and resists wash-off, thorough cleansing at the end of the day helps keep skin clear when using formulas rich in this silicone.
Summary
Bis-C30-45 Alkyl Dimethicone is mainly a skin-conditioning emollient. Its long hydrocarbon tails mimic natural oils while the silicone backbone delivers a silky glide, together forming a soft, flexible film that locks in moisture and smooths texture. Although less famous than classic dimethicone, it is gaining popularity in luxe moisturizers, primers and sunscreens that aim for a plush yet lightweight feel.
Safety data show it is generally well tolerated with a very low irritation or allergy rate. Still, skin can be unpredictable so patch testing a new product is wise to make sure it suits your individual needs.