What Is Peg-15 Butylene Glycol Diisostearate?
PEG-15 Butylene Glycol Diisostearate is a lab-made ingredient created by linking butylene glycol, a small alcohol often used to hold moisture, to isostearic acid, a fatty acid derived from vegetable oils. Chemists then attach roughly 15 units of ethylene oxide to this pair, giving the final material water-loving (hydrophilic) and oil-loving (lipophilic) ends. This balanced structure lets it mix oil and water smoothly.
The cosmetic industry began using PEG-based esters in the late 20th century when formulators looked for gentler alternatives to old soap-type cleansers. By tweaking the PEG length, they found PEG-15 Butylene Glycol Diisostearate offered a good mix of cleansing power and skin comfort, so it soon appeared in face washes and lotions.
Manufacturing starts with plant-sourced isostearic acid that is reacted with butylene glycol to form a diester. The product then undergoes ethoxylation, where ethylene oxide gas is added in a controlled reactor until the average chain length hits 15 units. The final liquid is filtered and purified to meet cosmetic grade standards.
You are most likely to see this ingredient in facial cleansers, creamy body washes, makeup removers, micellar waters, moisturizers and some leave-on masks where it helps keep the formula stable and soft on skin.
Peg-15 Butylene Glycol Diisostearate’s Cosmetic Benefits/Uses
This multitasker supports both the feel and performance of many personal care formulas.
- Cleansing: Its amphiphilic structure grabs onto oily grime with the fatty end while the PEG side stays in water, lifting dirt and makeup away without harsh stripping
- Emulsifying: Acts like a bridge between oil and water so creams and lotions stay smooth, preventing separation over time and giving products a pleasant glide
Who Can Use Peg-15 Butylene Glycol Diisostearate
Thanks to its balanced oil-and-water profile, Peg-15 Butylene Glycol Diisostearate is usually well tolerated by most skin types, including dry, oily, combination, sensitive and mature skin. Its mild cleansing action makes it gentler than traditional surfactants, so it rarely triggers tightness or flaking in dry or reactive complexions. Acne-prone users generally find it non-pore-clogging, although very blemish-prone skin should still monitor how any new product performs.
The ingredient is manufactured from plant-derived isostearic acid plus synthetic butylene glycol and ethylene oxide, with no animal by-products. That makes it suitable for vegans and vegetarians as long as the finished product has not been animal-tested and no other animal ingredients are present.
Current cosmetic safety assessments list Peg-15 Butylene Glycol Diisostearate as low risk for pregnant or breastfeeding women because the molecule is too large to penetrate deeply and is not known to interfere with hormones. This is not medical advice and anyone who is pregnant or nursing should have a doctor review all skincare products to be safe.
The ingredient is not known to cause photosensitivity and does not make skin more prone to sunburn. It also plays well with common actives like retinol and vitamin C, so layering products is generally uncomplicated.
Potential Side Effects/Adverse Reactions
Responses to topical Peg-15 Butylene Glycol Diisostearate vary from person to person. The effects listed below are possible yet uncommon when the ingredient is properly formulated in cosmetic products.
- Mild skin irritation — may present as redness or stinging on very sensitive skin, particularly if used in high concentrations or on compromised barriers
- Contact dermatitis — rare allergic reaction marked by itching, swelling or small bumps that subsides after discontinuation
- Eye irritation — if a cleanser containing the ingredient is not rinsed out of the eyes it can cause temporary burning or watering
- Over-cleansing related dryness — excessive or prolonged use of a product with surfactants can strip natural oils in some individuals
If any irritation, allergy or unexpected reaction occurs, stop using the product immediately and seek advice from a qualified healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1 out of 5
Peg-15 Butylene Glycol Diisostearate is a large, water-soluble ester that rinses away easily and does not stay on the skin long enough to block pores. Its fatty portion is branched rather than straight, which further reduces the chance of packing into pores and hardening. Formulation databases and supplier data show very few reports of breakout-related complaints, so it earns a low score of 1.
Suitable for acne-prone or easily congested skin, though individual responses can vary.
Worth noting: An entire formula’s comedogenic potential depends on the blend of ingredients, so a low-risk emulsifier like this can still sit inside an otherwise heavy cream that might clog pores.
Summary
Peg-15 Butylene Glycol Diisostearate acts mainly as a cleanser and an emulsifier. Its split personality, with one end that loves water and another that loves oil, lets it lift makeup and grime while keeping creams and washes smooth and uniform. Because it is mild, water-soluble and plant-derived, formulators appreciate it for gentle face washes, micellar waters and lightweight lotions, though it is not among the most talked-about ingredients on social media or beauty blogs.
Current safety assessments classify it as low risk for irritation, photosensitivity and systemic absorption. Most users can apply products containing this ester without issue, yet trying any new skincare should start with a patch test to confirm personal tolerance.