Probiotic, prebiotic or postbiotic: how not to overpay for a term

A probiotic is a live microorganism that confers a demonstrated benefit when administered in an adequate amount. A species name in INCI is not enough: strain identity, viability, quantity and a benefit under the stated conditions all matter.

A prebiotic is a substrate selectively used by host microorganisms that confers a benefit. Not every sugar or polysaccharide qualifies. A postbiotic is a preparation of inanimate microorganisms and/or their components with a demonstrated benefit. These are not interchangeable style words.

A ferment is material from a fermentation process, a lysate is produced by disrupting cells, and products of bacterial synthesis broadly describes substances of bacterial origin. These can be interesting parts of a formula, but their names alone say nothing about the result on skin.

To understand the material, you need the microorganism's identity, production method, standardisation and composition. A benefit for the finished cosmetic requires evidence on that specific formula.

One small study applied sonicated S. thermophilus to the forearms of 17 volunteers for seven days and observed an increase in stratum-corneum ceramides. Another study in 66 women with reactive skin reported changes in sensitivity and barrier measures after two months with a cream containing 10% B. longum lysate.

These are encouraging but narrow findings for specific materials and formulas. An early open-label study of live Roseomonas mucosa included just 10 adults and 5 children with atopic dermatitis and had no control group. None of these validates an entire cosmetic category.

Is the material live or inactivated? Is a strain or standardised preparation named? What amount or concentration is present in the finished formula? Is the material maintained across shelf life? Was this finished product studied for the promised outcome?

A missing answer does not make the formula bad. It means you should evaluate the complete INCI, intended use, texture and directions — without assuming that the product “restores the microbiome”.