Glycolic acid (or hydroxyacetic acid) is the smallest alpha-hydroxy acid (AHA). This colourless, odourless, and hygroscopic crystalline solid is highly soluble in water. Due to its excellent capability to penetrate skin, glycolic acid is often used in skin care products, most often as a chemical peel. It may reduce wrinkles, acne scarring, and hyperpigmentation and improve many other skin conditions, including actinic keratosis, hyperkeratosis, and seborrheic keratosis. Once applied, glycolic acid reacts with the upper layer of the epidermis, weakening the binding properties of the lipids that hold the dead skin cells together. This allows the outer skin to dissolve, revealing the underlying skin. It is thought that this is due to the reduction of calcium ion concentrations in the epidermis and the removal of calcium ions from cell adhesions, leading to desquamation. GlyAcid® delivers a formaldehyde free glycolic acid in a 70% solution (GlyAcid® 70 HP) and 99% crystalline (GlyAcid® 99 HP).