What Is Steareth-100?
Steareth-100 is a synthetic ingredient created by reacting stearyl alcohol, a waxy fatty alcohol usually sourced from vegetable oils, with ethylene oxide to attach roughly 100 repeating ethylene glycol units. The result is a long, water-loving chain paired with an oil-friendly tail, giving the molecule the ability to link oil and water. First explored in the mid-20th century as chemists looked for better ways to stabilize creams and lotions, Steareth-100 quickly found a place in personal care products because it solved the common problem of separating phases. Production involves controlled, high-pressure addition of ethylene oxide to purified stearyl alcohol, followed by filtration and safety testing. Today you will most often spot it in face masks, moisturizers, anti-aging creams, makeup removers, hair conditioners and rinse-off cleansers where a smooth, uniform texture is essential.
Steareth-100’s Cosmetic Benefits/Uses
Formulators reach for Steareth-100 because it delivers two key cosmetic functions that directly improve how a product looks, feels and performs on skin or hair:
- Gel forming – Steareth-100 helps create stable gels and emulsions so creams stay thick yet spreadable without splitting. This gives products a pleasing consistency and prevents watery runoff or greasy separation during storage or use
- Cleansing – By surrounding oil, dirt and makeup particles then helping them rinse away with water, Steareth-100 boosts the cleansing power of face washes, micellar waters and shampoo formulas leading to a fresher feel after rinsing
Who Can Use Steareth-100
Steareth-100 is generally considered suitable for all skin types including oily, combination, normal and dry skin because it has a lightweight non-occlusive feel and does not typically leave residue. Those with very sensitive or compromised skin should still monitor how their skin responds since any surfactant can occasionally disturb an already fragile barrier.
The ingredient is produced from stearyl alcohol that is usually plant derived, then chemically processed into a fully synthetic compound, so it is widely accepted by both vegetarians and vegans. If you follow a strict plant-only lifestyle, look for brands that confirm the original fatty alcohol is sourced from vegetable oils rather than animal fats.
No research suggests that Steareth-100 poses a special risk during pregnancy or while breastfeeding. This is not medical advice and anyone who is pregnant or nursing should ask their healthcare provider before introducing a new product just to be on the safe side.
Steareth-100 does not increase photosensitivity and will not make skin more prone to sunburn. It also has no known interactions with common actives like retinol or vitamin C when used in the same routine.
Potential Side Effects/Adverse Reactions
Side effects and reactions to the topical use of Steareth-100 vary from person to person. The points below outline potential issues although most users will not experience them when the ingredient is formulated correctly.
- Mild skin irritation such as redness or itching, most often in very sensitive individuals
- Contact dermatitis if the user is allergic to polyethylene glycol derivatives
- Transient eye stinging when a product containing Steareth-100 is rinsed inadequately from the eye area
- Dryness or tightness if used in a high concentration within a cleanser and left on the skin too long
If any unwanted reaction occurs stop using the product and consult a medical professional for advice.
Comedogenic Rating
Rating: 1 / 5 (low likelihood of clogging pores)
Steareth-100 is highly water soluble and is almost always used at small percentages as an emulsifying helper or cleansing aid. It rinses away cleanly instead of sitting on skin and forming a heavy film, which keeps its tendency to trap sebum and debris very low. For these reasons it earns a rating of 1 rather than a perfect 0 since, in theory, any surfactant blended with oils in a rich cream could contribute to congestion in very reactive skin.
Given the low rating, Steareth-100 is generally considered suitable for people who are prone to acne or breakouts.
Because it belongs to a family of polyethylene glycol (PEG) ethers, it is also non-ionic and unlikely to interact with oils in a way that converts them into pore-plugging residues, further supporting its low comedogenic score.
Summary
Steareth-100’s main jobs are to build stable gels and emulsions then assist in lifting away oil and dirt during cleansing. It does this by pairing a fatty stearyl tail that likes oil with a long chain of ethylene glycol units that love water, allowing it to bridge the two phases and keep formulas smooth while improving rinse off.
The ingredient enjoys steady popularity in skin care and hair care because it is dependable, cost effective and easy for chemists to work with, even if newer naturally derived emulsifiers sometimes steal the spotlight.
Current safety data classifies Steareth-100 as low risk for irritation or toxicity when used as directed. Still, everyone’s skin is unique, so perform a simple patch test whenever you try a new product that contains this or any other unfamiliar ingredient.