What Is Glycereth-18 Polyhydroxystearate?
Glycereth-18 Polyhydroxystearate is a plant-derived ingredient created by linking glycerin that has been treated with ethylene oxide to polyhydroxystearic acid, a fatty acid that comes from castor or other vegetable oils. This process produces a thick liquid ester that mixes well with both water and oil. Chemists started working with similar esters in the 1980s when water-in-oil creams grew popular, and this specific version soon found favor for its strong stabilizing power and mild skin feel. Manufacturing involves carefully reacting an 18-mole ethoxylated glycerin with polyhydroxystearic acid under controlled heat and pressure, then purifying the result to remove any leftovers from the reaction. You are most likely to spot Glycereth-18 Polyhydroxystearate in sunscreens, tinted moisturizers, long-wear foundations, rich night creams, clay or peel-off masks and other products that need oil and water to stay perfectly blended.
Glycereth-18 Polyhydroxystearate’s Cosmetic Benefits/Uses
This ingredient plays a key role in keeping a formula smooth and stable.
As an emulsion stabilizer it stops the oil and water phases in a lotion or cream from separating, which means the texture stays even from the first pump to the last. A stable emulsion also helps active ingredients spread evenly on the skin, improves the feel of the product and extends its shelf life.
Who Can Use Glycereth-18 Polyhydroxystearate
This stabilizer works well for nearly every skin type including dry, combination, oily and sensitive skin because it is gentle and has a light, non-greasy feel. People with very acne-prone skin usually tolerate it well, although breakout-prone users may want to check the whole formula since richer oils sometimes pair with this ingredient.
Because it is made from plant-based glycerin and fatty acids, Glycereth-18 Polyhydroxystearate is suitable for vegans and vegetarians. No animal-derived raw materials or by-products are involved in its manufacture.
The molecule sits on the surface of skin and is not known to penetrate deeply, so it is generally considered safe for those who are pregnant or breastfeeding. This is not medical advice and anyone who is expecting or nursing should ask a doctor before adding new skincare products, just to be safe.
The ingredient does not make skin more sensitive to the sun and can actually help keep UV filters evenly distributed in sunscreens. It also plays nicely with most other cosmetic ingredients, so formulators rarely run into compatibility issues.
Potential Side Effects/Adverse Reactions
Reactions to topical Glycereth-18 Polyhydroxystearate differ from person to person. The points below list potential side effects but most users will not experience them when the ingredient is used correctly in a finished product.
- Mild skin irritation: rare redness or stinging, usually in very sensitive or compromised skin
- Allergic contact dermatitis: uncommon itching or rash in those allergic to castor oil derivatives
- Eye irritation: temporary stinging if a product accidentally gets into the eyes
- Breakouts: possible clogged pores in individuals extremely prone to acne if the overall formula is heavy or occlusive
- Contaminant concerns: trace levels of ethylene oxide or 1,4-dioxane could remain if manufacturing is poorly controlled, though reputable suppliers remove them to meet safety limits
If you notice any discomfort or unwanted reaction stop using the product and consult a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1/5
Glycereth-18 Polyhydroxystearate contains fatty acid segments derived from castor oil yet its large, water-loving glycereth backbone keeps the molecule from nesting deeply inside pores. Most finished formulas use it at low levels strictly to stabilize emulsions so any pore-clogging potential is minimal.
Suitable for acne-prone or breakout-prone skin when used in lightweight or moderate formulations.
As with many PEG or ethoxylated ingredients, purity matters. Well-purified grades free of residual oils or waxes are least likely to add to pore congestion.
Summary
Glycereth-18 Polyhydroxystearate is an emulsion stabilizer that keeps water and oil perfectly blended which maintains a smooth texture, even distribution of actives and longer shelf life. It works by surrounding tiny oil droplets with a glycerin-rich shell that prevents them from merging back together.
While it is not the most famous name on an ingredient list, formulators value it for being reliable, gentle and vegan friendly, especially in sunscreens, long-wear makeup and rich creams.
Safety data show a low risk of irritation or sensitization when the ingredient is properly purified and used at standard levels. Still, skin is personal so patch testing any new product is a smart habit.