Polyhydroxy acids (PHAs) work by gently dissolving the keratin that binds our outermost layer of skin cells, encouraging the natural exfoliation process of the skin, leading to smoother, clearer skin. This process also encourages new skin cell generation in the basal layer of the epidermis, a process which naturally slows with age, so with repeated use this can have an overall anti-ageing effect on the skin. Gluconolactone has also been shown to inhibit the enzyme elastase, which breaks down elastin in the skin (an essential protein produced by the fibroblasts), leading to sagging of the skin.
PHAs are much larger in molecular weight vs AHAs so they cannot penetrate the skin as fast or as far, which therefore makes more gentle & suitable for more sensitive skin types, including those with rosacea-prone skin. Gluconolactone is also especially good for drier skin types as it also has natural humectant qualities, meaning it draws water towards it, hydrating the skin from within.