What Is Peg-175 Diisostearate?
Peg-175 Diisostearate is an ester created when diisostearic acid, a fatty acid that can be sourced from plant oils or synthesized, is joined to a long chain of polyethylene glycol consisting of about 175 repeating units of ethylene oxide. The end result is a large, waxy molecule that likes both oil and water, a trait that makes it valuable in cosmetic science. Polyethylene glycol based ingredients first showed up in creams and lotions in the 1950s as chemists looked for safer and more stable ways to blend oily and watery ingredients. Peg-175 Diisostearate is produced by first reacting isostearic acid with ethylene oxide under controlled heat and pressure, then purifying the product until it meets cosmetic grade standards.
Thanks to its dual love for oil and water it shows up in many leave-on and rinse-off products. You will find it in facial cleansers, cleansing balms, moisturizers, sheet mask essences, sunscreens, body lotions, hair conditioners and even some color cosmetics where a smooth, uniform texture is important.
Peg-175 Diisostearate’s Cosmetic Benefits/Uses
In formulas Peg-175 Diisostearate serves one key purpose that brings several practical benefits.
Emulsifying: It pulls oily and watery ingredients together so they stay mixed from the first pump to the last swipe. A stable emulsion feels silkier, spreads more evenly and delivers active ingredients more consistently. It also helps prevent the product from separating in the jar, extending shelf life and keeping the texture pleasant over time.
Who Can Use Peg-175 Diisostearate
This emulsifier is considered gentle enough for most skin types including dry, normal, oily and combination. People with easily upset or highly sensitive skin generally tolerate it well because it sits on the surface rather than penetrating deeply. Acne-prone users usually find it non clogging thanks to its low comedogenic rating, though individual results can vary.
Peg-175 Diisostearate is typically derived from plant-based fatty acids or made fully synthetically, so it is suitable for vegans and vegetarians as long as the finished product is certified cruelty free.
The large size of the molecule limits absorption, so it is not expected to pose a risk for women who are pregnant or breastfeeding. This is not medical advice, and anyone who is pregnant or nursing should ask a doctor before adding new skincare products, just to be safe.
The ingredient is not known to cause photosensitivity and does not make skin more reactive to sunlight. It also plays well with common actives like retinol, vitamin C and sunscreen filters without affecting their performance.
Potential Side Effects/Adverse Reactions
Reactions to topical Peg-175 Diisostearate differ from person to person. The issues listed below are possible but uncommon when the ingredient is used at the concentrations normally found in cosmetics.
- Mild skin irritation: A fleeting feeling of redness or warmth, usually in very sensitive users
- Contact allergy: Rare cases of itching or small bumps if the immune system identifies the molecule as a trigger
- Eye stinging: Temporary discomfort if a product containing the ingredient gets into the eyes before rinsing
- Product build-up on hair: In leave-on conditioners very fine hair may feel weighed down if the formula is rich in this emulsifier
- Impurity concerns: If poorly purified during manufacturing trace 1,4-dioxane could be present, though reputable brands test to keep levels far below safety limits
If any negative reaction occurs stop using the product and consult a healthcare professional.
Comedogenic Rating
Rating: 1/5
Peg-175 Diisostearate sits on the surface rather than sinking into pores and its large PEG backbone keeps the fatty portion from behaving like a heavy oil. Tests and user reports show little tendency to trap sebum or form blockages, which is why it earns a low score of 1. In practical terms it is generally suitable for people who are prone to acne or breakouts. Formulas that combine it with highly occlusive butters or waxes could push overall comedogenicity higher, so the full ingredient list still matters.
Summary
Peg-175 Diisostearate is mainly an emulsifier that binds oil and water so creams, lotions and cleansers stay smooth and stable. Its amphiphilic structure—part fatty, part water loving—lets it form a microscopic bridge between the two phases which improves texture, spreadability and shelf life.
While not a household name like glycerin or hyaluronic acid it is quietly popular with formulators because it is reliable, mild and compatible with a wide range of active ingredients.
Current safety assessments find it low risk when used in the tiny amounts typical for cosmetics. Nonetheless every skin type is unique, so performing a quick patch test when trying any new product containing Peg-175 Diisostearate is always a smart move.