What Is Peg-66 Trihydroxystearin?
Peg-66 Trihydroxystearin is a plant-derived ingredient created by attaching roughly sixty-six units of ethylene oxide to trihydroxystearin, a triglyceride made from castor or other vegetable oils rich in ricinoleic acid. The result is a creamy wax-like substance that dissolves in both water and oil, giving it impressive versatility in cosmetic formulas.
Chemists first explored ethoxylated castor derivatives in the mid-20th century while searching for gentler alternatives to soap. Over time Peg-66 Trihydroxystearin proved especially useful for modern rinse-off cleansers and water-in-oil creams, earning a place on ingredient lists for decades.
Production starts with the hydrogenation of natural castor oil to obtain 12-hydroxystearic acid. Three of these fatty acid molecules are then esterified with glycerin to form trihydroxystearin. Finally, controlled ethoxylation grafts the polyethylene glycol (PEG) chains onto the molecule, giving it the ability to mix oil and water smoothly.
You are most likely to spot Peg-66 Trihydroxystearin in facial cleansers, makeup removers, clay or cream masks, moisturizing lotions, sunscreens, cream foundations and certain anti-aging serums where a stable, silky texture is essential.
Peg-66 Trihydroxystearin’s Cosmetic Benefits/Uses
This multi-tasking ingredient improves both the feel and performance of a broad range of personal care products.
- Cleansing: Helps lift away excess oil, dirt and makeup without harsh surfactants, leaving skin feeling clean yet comfortable
- Emulsifying: Binds oil and water phases so products stay smooth and uniform, preventing separation while giving formulations a soft, non-greasy finish
Who Can Use Peg-66 Trihydroxystearin
This versatile emulsifier suits most skin types including dry, combination, oily and even sensitive skin because it is gentle and free of common irritants like fragrance or essential oils. Those with extremely acne-prone skin can still benefit, though they may prefer light formulations that pair the ingredient with non-occlusive oils.
Peg-66 Trihydroxystearin is manufactured from plant oils and synthetic ethylene oxide, so it fits vegan and vegetarian preferences as long as the finished product does not include animal-derived additives.
The ingredient is regarded as low risk for people who are pregnant or breastfeeding. That said, this is not medical advice and anyone expecting or nursing should show their healthcare provider the full ingredient list of any product they plan to use to be certain it aligns with their individual needs.
Peg-66 Trihydroxystearin does not absorb ultraviolet light and is not known to cause photosensitivity. It can therefore be worn day or night without increasing sun sensitivity. There are no special storage or application concerns beyond normal cosmetic hygiene.
Potential Side Effects/Adverse Reactions
Responses to Peg-66 Trihydroxystearin vary from person to person. The points below outline potential side effects but most users experience none of these issues when the ingredient is used at typical cosmetic levels.
- Mild skin irritation: temporary redness or itching, most often in very reactive skin
- Contact dermatitis: rare inflammatory reaction in individuals allergic to polyethylene glycol compounds
- Eye stinging: possible if a cleanser or cream accidentally reaches the eye area before rinsing
- Allergic reaction: extremely uncommon hives or facial swelling requiring prompt medical attention
- Enhanced penetration of actives: by helping ingredients mix evenly the emulsifier can increase the strength of potent acids or retinoids applied in the same formula, indirectly raising irritation risk
If you notice any adverse effect stop using the product immediately and seek advice from a qualified healthcare professional.
Comedogenic Rating
Comedogenic rating: 1/5. Even though Peg-66 Trihydroxystearin is built from a fatty acid, the large PEG chains make the molecule highly water loving which keeps it from lodging in pores. Tests on similar PEG-castor blends show little to no pore clogging, so most people will not see new blackheads or bumps from this ingredient. In short it is generally safe for acne-prone skin when used in well-balanced formulas. If a breakout does occur it is more likely due to heavier oils or waxes paired with it than the emulsifier itself.
Summary
Peg-66 Trihydroxystearin works as a gentle cleanser and reliable emulsifier. Its fatty backbone grabs onto oils and dirt while the PEG side mixes easily with water, letting grime rinse away without stripping skin. The same dual nature holds oil and water phases together in creams or lotions, creating a smooth stable texture that feels light yet cushy on the skin.
It is a quiet workhorse rather than a buzzword ingredient; you will spot it in many cleansers, masks and hybrid skincare-makeup products but it rarely gets top billing on the label. Safety profiles from regulators and manufacturers place it in the low-risk category with only rare reports of irritation or allergy.
Most users can enjoy products containing Peg-66 Trihydroxystearin with confidence, though it is always smart to patch test a new formula to be sure it suits your individual skin.