Sodium Isostearate

Sodium Isostearate's CosIng-listed function is "surfactant - cleansing": helps remove dirt and oil. This describes a formula role, not a tested finished-product benefit.

A patch-test caution, not a hard avoid. A 1995 lab study found Malassezia furfur really does hydrolyse synthetic fatty-acid esters back into free fatty acids — ethyl esters (like ethyl oleate) fastest, isopropyl esters (isopropyl palmitate, isopropyl myristate) next — and the released unsaturated fatty acids fed the yeast's growth more than saturated ones did. So the mechanism is real for at least some esters. But this remains the biggest over-flagging bucket: many ubiquitous emulsifiers (glyceryl stearate, PEG-100 stearate) are built so the fatty acid isn't released in a usable form, and many fungal-acne-prone people tolerate them fine, especially in rinse-off. Treat a match as 'worth patch-testing', not 'certainly breaks you out'.

Evidence: Moderate evidence.

• Mayser P, et al. Hydrolysis of fatty-acid esters by Malassezia furfur — ethyl esters hydrolysed fastest, then isopropyl esters; released unsaturated fatty acids stimulated growth. Acta Derm Venereol 1995. PubMed
• Fungal Acne and Lipids: What Science Actually Says (concentration-dependence & over-flagging critique). Roccoco

Sodium Isostearate appears in 0% of the 7,133 decoded products in our catalog (3 products). This describes our recorded ingredient lists, not the whole skincare market.

In the products we've decoded, Sodium Isostearate appears in formulas from Payot, Bielenda.

In our decoded catalog, Sodium Isostearate shows up mostly in moisturizers (2), serums (1).

Based on the categories of the decoded products that list it, Sodium Isostearate shows up mostly in leave-on products (3 of 3 classified). This is derived from product category, not a label fact.

On Korean labels, Sodium Isostearate is listed as 소듐아이소스테아레이트.