Yogurt, when used as a cosmetic ingredient, typically refers to processed yogurt derivatives such as yogurt powder, yogurt filtrate, or fermented milk extracts rather than fresh food-grade yogurt. These materials are rich in lactic acid, milk proteins (casein and whey fractions), lipids, minerals, and fermentation-derived metabolites, which collectively contribute to their functional value in topical formulations. In skincare, yogurt-derived ingredients are primarily appreciated for their mild exfoliating activity, driven by naturally occurring lactic acid (an alpha-hydroxy acid), alongside their hydrating and barrier-supportive properties. The presence of milk proteins and lipids supports surface conditioning, while fermentation byproducts may help maintain a balanced skin environment.

In hair care applications, yogurt-based ingredients act mainly as conditioning and smoothing agents, improving hair feel, softness, and surface cohesion. Milk proteins can temporarily bind to damaged cuticle regions, enhancing hair fiber integrity and reducing friction, while lactic acid derivatives may help smooth the cuticle by supporting an optimal pH range. Additionally, yogurt ferment components are sometimes positioned as microbiome-friendly ingredients, although most benefits remain cosmetic rather than biological. Due to variability in raw material composition, yogurt derivatives are most effective when standardized and incorporated into rinse-off products, masks, or conditioning treatments where stability constraints can be carefully managed.