Peg-15 Hydrogenated Castor Oil Isostearate: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: July 1, 2025
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We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Peg-15 Hydrogenated Castor Oil Isostearate?

Peg-15 Hydrogenated Castor Oil Isostearate is a plant-derived ingredient made from castor oil that has been fully hydrogenated, reacted with about fifteen units of ethylene oxide, and then combined with isostearic acid. This process turns the thick, sticky original oil into a smooth wax-like substance that blends easily with water and oil. The technique became popular in the late twentieth century as brands looked for gentler alternatives to petroleum-based surfactants. Today it is manufactured in large reactors where castor oil is first hydrogenated to make it solid, then ethoxylated to add the PEG part, and finally esterified with isostearic acid for extra mildness and stability. You will typically find it in face and body moisturizers, sunscreens, cleansing balms, makeup removers, hair conditioners, sheet mask essences and many leave-on skin treatments that aim to feel light yet creamy.

Peg-15 Hydrogenated Castor Oil Isostearate’s Cosmetic Benefits/Uses

This multitasking ingredient helps a formula look better, feel better and stay mixed over time.

  • Emulsifying – keeps water and oil evenly blended so creams do not split, giving a stable texture that feels silky on the skin
  • Viscosity controlling – adjusts thickness, letting chemists create lotions that are either rich and cushiony or light and fluid without adding heaviness

Who Can Use Peg-15 Hydrogenated Castor Oil Isostearate

This ingredient is generally friendly to all skin types including dry, oily, combination and sensitive skin because it is non reactive and has a light, non greasy feel. Extremely acne prone users should note that it is derived from castor oil so very occasional clogged pores are possible, though uncommon, when formulas are overloaded with it.

Peg-15 Hydrogenated Castor Oil Isostearate is plant based and produced without any animal derivatives so it is considered suitable for both vegetarians and vegans.

Current safety data shows no specific risks for pregnant or breastfeeding women. That said this is not medical advice and anyone who is expecting or nursing should review new skincare products with a healthcare professional before use just to be safe.

The ingredient does not increase photosensitivity and will not make skin more prone to sunburn. It is also fragrance free and free of common allergens such as gluten, nuts and soy.

Potential Side Effects/Adverse Reactions

Reactions to topical Peg-15 Hydrogenated Castor Oil Isostearate differ from person to person. The points below outline potential issues only. When the ingredient is properly formulated most users will not notice any of these effects.

  • Mild skin irritation – rare tingling or redness, most often in very sensitive or compromised skin
  • Allergic contact dermatitis – isolated cases of rash or itching in individuals already allergic to polyethylene glycols or castor derivatives
  • Acne flare ups – possible clogged pores in those with highly occlusive routines or severe acne prone skin
  • Eye stinging – temporary discomfort if a product containing it accidentally enters the eyes

If any discomfort, persistent redness or breakouts occur discontinue use and consult a healthcare professional

Comedogenic Rating

Rating: 1 / 5

Peg-15 Hydrogenated Castor Oil Isostearate is largely water dispersible thanks to its PEG chains so it does not linger inside pores like heavier straight oils. Its waxy but non-occlusive texture gives formulas slip without forming a thick film that traps debris. Only very rich products that already layer several oils and waxes might inch this score higher.

With a low rating it is generally fine for skin that is prone to acne or breakouts.

Real-world clogging risk depends on the whole recipe. Pairing this ingredient with heavy butters or high-level silicones can raise overall comedogenicity even if the raw material itself stays low.

Summary

Peg-15 Hydrogenated Castor Oil Isostearate stabilises oil-and-water mixes and lets chemists tweak thickness without greasiness. Its castor oil tail grabs onto oily phases while the PEG section pulls toward water holding everything together and creating smooth spreadable textures.

It is not a trendy headline ingredient yet it appears in countless everyday moisturisers sunscreens and cleansing balms because it simply works.

Current research shows it is safe for most users with only rare irritation or allergy reports. As with any new product a quick patch test is a smart precaution before full use.

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