What Is Isosteareth-6 Carboxylic Acid?
Isosteareth-6 Carboxylic Acid is a synthetic ingredient made by attaching roughly six units of ethylene oxide to isostearyl alcohol, then adding a carboxylic acid group. The result is a mild, water loving fatty acid that acts as a nonionic surfactant. Chemists started creating this class of materials in the mid-1900s to make gentler cleansers and more stable creams than older soap-based formulas. Production begins with fatty alcohols usually sourced from plant oils or petroleum. These are ethoxylated under heat and pressure, then reacted with chloroacetic acid to introduce the final carboxyl group. The finished ingredient appears as a waxy solid or thick paste that dissolves easily in warm water or oils.
You will spot Isosteareth-6 Carboxylic Acid in facial cleansers, makeup removers, micellar waters, toners, body washes, lotions, sunscreens, anti-aging creams, wash-off masks and even some hair conditioners. Its balance of oil affinity and water solubility lets formulators create products that feel light yet still rinse away dirt and makeup.
Isosteareth-6 Carboxylic Acid’s Cosmetic Benefits/Uses
Below are the key ways this ingredient improves a formula
- Cleansing – Its surfactant nature lifts oils, sweat and makeup from skin then helps them rinse away with water, leaving a fresh feel without a tight after-feel
- Emulsifying – It keeps water and oil evenly blended so creams, lotions and sunscreens stay smooth, resist separation and deliver active ingredients uniformly with every use
Who Can Use Isosteareth-6 Carboxylic Acid
This ingredient is generally well tolerated by normal, oily, combination and even dry skin because it cleanses without stripping away too much natural oil. Sensitive or eczema-prone skin can usually handle it too, but very reactive complexions might notice a bit of tightness if the overall formula contains a high level of surfactants.
Isosteareth-6 Carboxylic Acid is synthesized from plant oils or petroleum derivatives, not animal sources, so it is typically suitable for vegans and vegetarians. If the finished product carries a vegan claim it means the manufacturer has verified this supply chain.
No studies link this ingredient to hormonal disruption or fetal risk, so pregnant or breastfeeding users can use products containing it. This is not medical advice and anyone who is expecting or nursing should still discuss every new skincare product with a qualified doctor just to be safe.
It does not make skin more sensitive to sunlight, so there is no added risk of sunburn or discoloration. The only extra point to note is that as a surfactant it may allow other active ingredients in the same formula to penetrate a little better, which can be helpful or irritating depending on what else is in the product.
Potential Side Effects/Adverse Reactions
Reactions to topical Isosteareth-6 Carboxylic Acid vary from person to person. The points below list potential side effects that could occur, but most people will not experience them when the ingredient is used at the levels normally found in cosmetics.
- Mild skin irritation such as redness or stinging, especially on very sensitive skin
- Contact dermatitis in individuals allergic to polyethylene glycol type ingredients
- Dry or tight feeling if used in a formula that is otherwise low in moisturizers
- Temporary eye irritation if the product accidentally gets into the eyes
- Enhanced penetration of stronger actives in the same product which could amplify their own irritation potential
If any of these effects occur stop using the product and consult a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1/5. Isosteareth-6 Carboxylic Acid is a lightweight nonionic surfactant with a short ethoxylated chain that rinses away easily and does not leave a heavy film. It is far less greasy than traditional fatty acids or esters that commonly clog pores. While any surfactant can interact with skin oils and residue, the molecular size and quick rinse profile of this ingredient keep pore blockage risk low.
Overall it is usually fine for acne-prone or breakout-prone skin, provided the rest of the formula is also low in comedogenic components.
As with most surfactants, overuse or pairing with rich occlusives could indirectly increase congestion, so product context matters.
Summary
Isosteareth-6 Carboxylic Acid acts mainly as a cleanser and emulsifier. Its balanced lipophilic tail grabs oils while its ethoxylated, carboxylated head bonds with water, letting grime wash away and keeping oil-water blends stable in creams and washes.
It is a workhorse ingredient that shows up in many mainstream cleansers, makeup removers and lotions but it is not a buzzworthy star, so most shoppers are unaware of it by name.
Safety reviews find it low risk with only rare irritation or allergy. Still, skin is personal so test new products on a small patch before full use.