Gluconolactone or polyhydroxy acid is an ingredient which efficiently resolves the problem of photo damaged skin in which the abnormal appearance of solar elastosis has repressed the collagen rich extracellular matrix. The culprits for activating solar elastosis are free radicals whose actions may be cancelled out only by the application of a complex of antioxidants and exfoliators which stimulate cell renewal. Polyhydroxy acid or PHA is a close relative to AHA or alpha hydroxy acid (glycolic and lactic acid), yet there is a difference between them as far as effectiveness of exfoliation and level of photosensitisation of the skin due to which using a combination of the two in one product gives the best results.
Even though they act as very mild exfoliators, as opposed to AHAs which perform that task much better, PHAs have a photoprotective effect on the skin whereby reducing the photosensitising effect that AHAs have on the skin (source: Bernstein E.F. et al 2004 The Polyhydroxy Acid Gluconolactone Protects Against Ultraviolet Radiation in an In Vitro Model of Cutaneous Photoaging Dermatological Surgery, 2:189-196). Simply put, we could say that by combining AHA and PHA ingredients we get an exfoliating cocktail that, when compared to other AHA exfoliators, photosensitises the skin to the minimum. As a gentle relative to alpha hydroxy acids, gluconolactone improves texture and uneven skin tone, reduces the size of pores and raises the skin’s moisture levels (ibid., 194), yet in combination with small percentages of lactic and glycolic acid, as in Skintegra’s Lumion, that effect is even more potent.