What Is Peg-4 Sorbitan Triisostearate?
Peg-4 Sorbitan Triisostearate is an emulsifier created by linking sorbitol, a sugar alcohol often sourced from corn or wheat, with three units of isostearic acid obtained from plant-based fatty acids. Four units of ethylene oxide are then added to the sorbitan backbone, giving the molecule its “PEG-4” designation and a water-loving character. This blend of oil-friendly and water-friendly parts lets it sit at the interface of oil and water, a key trait for keeping lotions or creams from separating.
Interest in sorbitan esters began in the mid-20th century when formulators were searching for gentle alternatives to soap-type emulsifiers. By adding small amounts of polyethylene glycol, chemists increased the solubility of these esters in water, resulting in the PEG sorbitan family used widely today. Peg-4 Sorbitan Triisostearate earned a place in modern cosmetics thanks to its balance of mildness, stability, and reliable performance under a range of pH and temperature conditions.
Industrial production involves esterifying sorbitol with isostearic acid under controlled heat, followed by ethoxylation where ethylene oxide gas reacts with the molecule inside a closed reactor. The finished ingredient is a soft wax or thick liquid that blends easily into both aqueous and oil phases during manufacturing.
You will typically find Peg-4 Sorbitan Triisostearate in moisturizers, sunscreens, cleansing balms, makeup removers, BB creams, color cosmetics such as foundations or lipsticks, and leave-on hair conditioners where it helps distribute oils evenly and improves overall texture.
Peg-4 Sorbitan Triisostearate’s Cosmetic Benefits/Uses
The primary benefit of Peg-4 Sorbitan Triisostearate lies in its ability to keep oil and water mixed, ensuring a smooth stable product throughout its shelf life and during use.
Who Can Use Peg-4 Sorbitan Triisostearate
This emulsifier is generally considered suitable for all major skin types including dry, oily, combination and sensitive skin because it stays on the surface and does not noticeably alter the skin’s natural barrier. People with very sensitive or compromised skin should still watch for any formula that pairs it with harsh solvents since those could be the real irritants rather than the emulsifier itself.
Peg-4 Sorbitan Triisostearate is made from plant derived sorbitol and fatty acids then reacted with ethylene oxide, none of which come from animal sources. For that reason it is typically labeled vegan and vegetarian friendly, though certification depends on the final manufacturer’s supply chain.
Current safety data show no specific risks for pregnant or breastfeeding women when the ingredient is used topically in cosmetics. This is not medical advice and anyone who is pregnant or nursing should ask their doctor before introducing new skincare products just to be safe.
The ingredient does not increase photosensitivity, so it will not make skin more prone to sunburn. It is also odorless and non volatile, making it unlikely to trigger headaches in fragrance sensitive users.
Potential Side Effects/Adverse Reactions
Side effects and reactions to the topical application of Peg-4 Sorbitan Triisostearate can vary from person to person. The following is a list of potential side effects that are possible yet uncommon when the ingredient is properly formulated in a cosmetic product
- Mild skin irritation such as redness itching or stinging
- Allergic contact dermatitis in individuals already sensitized to polyethylene glycol derivatives
- Eye irritation if a product accidentally gets into the eyes
- Increased penetration of other ingredients that may be irritating because the emulsifier can improve their spreadability
- Very rare sensitization leading to hives or rash after repeated exposure
If you experience any of these effects stop using the product and seek advice from a qualified healthcare professional
Comedogenic Rating
Rating: 1 out of 5
Peg-4 Sorbitan Triisostearate sits mostly on the surface and is highly water dispersible thanks to its four ethylene oxide units. This reduces the chance that it will clog pores compared with heavier un-ethoxylated fatty esters. The small amount of plant-derived isostearic acid it carries could in theory add a slight occlusive feel, which is why it earns a 1 rather than a perfect 0.
It is generally suitable for acne-prone or breakout-prone skin because its pore-blocking potential is very low.
Available test data on comedogenicity are limited but similar PEG sorbitan esters have shown minimal to no pore clogging in rabbit ear assays, the traditional benchmark used by formulators.
Summary
Peg-4 Sorbitan Triisostearate is an oil-in-water emulsifier that works by parking its water-loving PEG portion in the aqueous phase while its fatty isostearate anchors in the oil phase, creating a stable bridge between the two. This keeps creams lotions makeup and even some hair products from separating, improves texture and helps active ingredients spread evenly.
While not as high-profile as polysorbate 20 or sorbitan oleate it enjoys steady popularity among formulators who want a mild plant-based option that tolerates a wide pH range and resists heat stress during manufacturing.
Current safety reviews classify it as low risk for irritation or sensitization when used at typical cosmetic levels. Still everyone’s skin is unique so performing a quick patch test when trying a new product that contains this emulsifier is a smart precaution.