What Is Sodium Isosteareth-11 Carboxylate?
Sodium Isosteareth-11 Carboxylate is a synthetic ingredient made by reacting isostearyl alcohol with ethylene oxide, then converting the resulting polymer into its sodium salt form through carboxylation. The name hints at its makeup: “isosteareth” points to an isostearic acid-derived alcohol, “11” notes an average of eleven ethylene oxide units, and “carboxylate” signals the final step that gives it a mild anionic character. This blend of a fatty chain and a string of water-loving oxyethylene units lets it sit comfortably at the oil-water border inside a formula.
The ingredient appeared in the late twentieth century when formulators began looking for gentler surfactants that could clean skin without stripping it. By tweaking well-known polyethylene glycol (PEG) chemistry and pairing it with isostearic acid, chemists created a molecule that balances cleansing power with a soft after-feel. Today it is produced in large-scale reactors where temperature, pressure and pH are carefully controlled to ensure a consistent eleven-unit average.
You are most likely to find Sodium Isosteareth-11 Carboxylate in rinse-off products that need to both lift away dirt and keep textures stable. It shows up in facial cleansers, micellar waters, shampoos, body washes, baby washes, creamy scrubs, sheet mask serums and even some lightweight lotions that need self-emulsifying properties.
Sodium Isosteareth-11 Carboxylate’s Cosmetic Benefits/Uses
Here is how this multitasker helps a formula perform and feel better on skin:
- Cleansing: Its anionic head binds to water while the fatty tail hugs oil and debris, letting them rinse away easily. This means a cleanser can remove makeup, sunscreen and excess sebum without aggressive foaming agents, leaving skin feeling fresh yet comfortable.
- Emulsifying: It bridges oils and waters so lotions and washes stay smooth and uniform over shelf life. By stabilizing the mix it prevents separation, delivers an even dose of active ingredients and gives products a pleasant, silky glide during application.
Who Can Use Sodium Isosteareth-11 Carboxylate
This ingredient is generally well tolerated by all skin types. Its mild cleansing action works for normal and combination skin while the added fatty chain helps keep dryness in check for dry skin. Sensitive or easily irritated skin usually handles it well because it creates a soft, low-foam lather that does not aggressively strip the barrier.
Sodium Isosteareth-11 Carboxylate is synthesized from plant-derived isostearic acid and petro-based ethylene oxide, with no animal inputs, so it is suitable for vegans and vegetarians.
Current safety data do not flag any special concerns for people who are pregnant or breastfeeding. Still this is not medical advice and anyone expecting or nursing should run any skincare product past a healthcare professional just to be safe.
The molecule does not absorb UV light or affect the way skin responds to sunlight so it is not linked to photosensitivity. It also plays nicely with most other common skincare actives, making formulation conflicts unlikely.
Potential Side Effects/Adverse Reactions
Responses to topical use can vary from person to person. The points below outline potential but uncommon side effects. In properly formulated products most users experience none of these issues.
- Mild skin irritation such as redness or itching, especially on very compromised skin
- Transient stinging if the formula gets into the eyes
- Dry or tight feeling when used in very high concentrations or paired with other strong surfactants
- Rare cases of allergic contact dermatitis for individuals sensitised to ethoxylated compounds
If you notice any uncomfortable reaction stop using the product and consult a healthcare professional.
Comedogenic Rating
Rating: 1 out of 5
Sodium Isosteareth-11 Carboxylate carries a very low risk of clogging pores because its molecule is highly water soluble and is usually found in rinse-off products that spend little time on skin. The fatty part is balanced by eleven hydrophilic oxyethylene units, so it does not sit in pores or form heavy films. Most people prone to acne or breakouts can use products containing this ingredient without added concern.
Since formulas that include it often contain other oils or waxes, keep in mind that overall product composition, not this single ingredient, determines pore-clogging potential.
Summary
Sodium Isosteareth-11 Carboxylate works as a mild cleanser and an efficient emulsifier. Its anionic head grips water while its fatty tail grabs oil so dirt, makeup and sebum lift away during rinsing. The same dual nature stabilizes oil-in-water mixes, keeping lotions and washes smooth and uniform.
It is a behind-the-scenes helper rather than a superstar headline, so you may not see it advertised yet it appears regularly in gentle facial cleansers, baby washes and micellar waters where a soft feel is prized.
Current safety reviews rate it as low risk with only rare irritation reports. While most users enjoy trouble-free results, it is always wise to patch test any new product to catch personal sensitivities early.