 There is a reason why there's a long historical use of fruit purées as facial masks, and perhaps why Cleopatra was said to bathe in sour milk. Alpha hydroxy acids, also known as fruit acids, are natural acids found in foods. They include citric acid from citrus, glycolic acid from sugarcane, lactic acid from fermented fruits, malic acid from a variety of fruits, and tartaric acid from grapes. High-strength concentrations are used for chemical peals. Over 40% can only be used by medical doctors. Professionals in salons can give more mild peals with 10-40% acid solutions, but concentrations under 10% are sold over-the-counter as exfoliants. Alpha hydroxy acids are thought to work by weakening cell-to-cell bonds to hasten the shedding of dead cells off the skin surface. Three placebo-controlled studies of over-the-counter strengths have been published. The first compared an 8% glycolic acid lotion to an 8% lactic acid lotion to a placebo lotion applied daily on face and forearms for 22 weeks. Both the acids work similarly, producing visible improvements in facial photodamage and more than 70% of the acid groups versus only 40% of the placebo group. All the participants were advised to wear protective clothing and regularly use sunscreen, which may explain the benefits even in the placebo group. Overall forearm photodamage and salinus also improved significantly in the acid versus placebo groups. About one in three participants experienced transient redness, but only one out of 74 left to study due to facial irritation. The second trial found a 5% glycolic acid lotion for three months beat out placebo on lessening skin roughness and model discoloration on the face and neck, but failed to significantly reduce wrinkle scores. The irony of alpha hydroxy acids is that while they can help with past photodamage, they can make future damage worse by increasing skin photosensitivity. So taking precautions is recommended. The FDA recommends that all alpha hydroxy products be labeled with a prominent warning sunburn alert. This product may increase your skin sensitivity to the sun, and particularly the possibility of sunburn, use a sunscreen where protective clothing and limit sun exposure while using this product and for a week afterwards. What about ascorbic acid, also known as vitamin C? If niacinamide works by turning into antioxidants, why not just apply antioxidants directly? Topical application can lead to vitamin E levels in the skin 10 times what is achieved by oral dosing and vitamin C up to 40 times higher, at least in mouse and big skin, respectively. According to a review on topical anti-aging skincare by a prominent Beverly Hills plastic surgeon, at a minimum, patients should be encouraged to use daily sunscreen, topical retinoid every night, and a topical antioxidant daily. But there's only one antioxidant that's been clearly shown to work. Despite its ubiquity in skin care products, there's no evidence to support any role for topical vitamin E in skin aging, whether for wrinkles, discoloration, or texture. The one study on topical CoQ-10 also failed to work significantly better than placebo, but there is one type of vitamin C that has been shown to help. Skin biopsy studies show that the topical application of a 5% solution of L ascorbic acid, also known as just ascorbic acid, the type of vitamin C found in food, significantly increases the expression of collagen in human skin compared to the placebo, suggesting functional activity of the skin cells is not maximal in postmenopausal women and can be increased. A split face study involving the application of three drops of a 10% L ascorbic solution for three months found significant improvements over the placebo side of the face in fine and coarse wrinkles, sourness, and skin tone or firmness. Not knowing which side was which, 16 out of 1984% of patients correctly identified the vitamin C side as the one showing improvement. Unfortunately, L ascorbic acid is unstable in creams, turning an unsightly ground when it oxidizes, limiting its shelf life. So instead, the skin care industry uses more stable vitamin C esters or derivatives, such as ascorbic palmitate, magnesium, ascorbic phosphate, ascorbic acid sulfate, ascorbic stearate, et cetera. Unfortunately, there is no evidence that these compounds have comparable effects, likely because they're poorly absorbed and only minimally convert to the active form. The good news is that you can make your own. Although vitamin C concentration is lowest 3% or 5% have been shown to have anti-wrinkle effects in split face or split neck and arm studies, 10% is recommended. The 10% solution used in this study retails for a ridiculous $127 per ounce. You can make a DIY solution more than 2,000 times cheaper, simply by buying L ascorbic acid in bulk and mixing 3 grams into 30 grams of water at a cost of about a nickel per ounce. You can mix it in an eyedropper and drip four to five drops on the palm of your hand and use your fingertips to apply over your face, neck, and upper chest daily. Just be careful to not get any in your eyes.