In daily use of skin care products, there are a few products that contain various “acid” ingredients. What are the effects of these skin care products? How to choose the right “acid” skin care products? Now we will take you to recognize. Salicylic Acid Salicylic acid is extracted from willow leaves or willow bark, so it is also called willow acid, and its chemical structure belongs to the beta hydroxy acid, i.e., BHA. for nearly a hundred years, dermatologists have been using salicylic acid to treat a variety of skin diseases. Unlike fruit acids (AHA), salicylic acid is fat-soluble (oil-soluble) and has good permeability to the skin, penetrating into lipid-rich pores and cleaning them deeply. In addition, salicylic acid has a stronger anti-inflammatory effect and is more effective in treating inflammatory acne (red acne as well as acne with pustules), as well as inflammatory skin disorders such as rosacea (rosacea) in the papule and pustule stage, and seborrheic dermatitis. Salicylic acid has whitening and rejuvenating effects, improves wrinkles, minimizes pores, and is the most basic and effective exfoliating factor. Salicylic Acid is approved by FDA of U.S. Food and Drug Administration, it can get rid of aging keratinocytes and let the healthy cells newborn to achieve the effect of whitening and lightening pigmentation. Salicylic acid is a good acne, skin care products, the U.S. FDA recommended concentration of 0.5-2%, the skin is particularly sensitive people can use a lower concentration, in general, the use of 2% of the concentration of the most appropriate. Almost all brand-name cosmetics contain salicylic acid, the purpose of which is to strengthen the exfoliation, chicken skin, whitening, spot removal, anti-inflammatory effect, while allowing the skin to become smooth and white. What has been widely used in recent years is supramolecular salicylic acid, which enables salicylic acid to be dissolved in water without the use of any organic solvents such as alcohol and slowly releases salicylic acid for 12 hours while maintaining a low pH value, thus effectively reducing the irritation of salicylic acid while improving its bioavailability. It can be said that supramolecular salicylic acid greatly circumvents the irritating side effects of traditional salicylic acid, while at the same time utilizing the positive energy of salicylic acid. Fruit acid Fruit acid is a class of organic acids, including glycolic acid, lactic acid, amygdalic acid, malic acid, citric acid, etc. Usually people commonly known as fruit acids for glycolic acid, was added to the skin care products in the most is also glycolic acid, applied to anti-acne on the main glycolic acid and amygdalic acid, the former molecular weight is the smallest, can reduce the epidermal interstitial coagulation of the cell mass, so that the follicles of fungal part of the angular prion cells to reduce the adhesion so as to achieve the purpose of removing pimples. The former has the smallest molecular weight and can reduce the cohesion of the epidermal interstitial cells, so that the adhesion of the keratinocytes in the follicle funnels can be reduced, thus achieving the purpose of acne removal. After penetrating into the skin, the low concentration of fruit acids (below 3%) will encourage the skin to synthesize more mucopolysaccharides, hyaluronic acid and ceramides, which will have a moisturizing effect and at the same time strengthen the barrier function of the skin to resist more external stimuli. When the concentration rises to 4% and the pH drops below 4, the product has a mildly exfoliating effect. To ensure safe use, the pH is also higher than 3. As the concentration of fruit acids continues to increase, the exfoliating power becomes more powerful, resulting in a “peel”. This is a dangerous procedure that should only be done by professionals. A-acid A-acid and vitamin A are compounds that can be transformed into each other in the body, mainly affecting bone growth and promoting metabolic effects such as epithelial cell proliferation, differentiation and keratolysis. It is used in the treatment of acne vulgaris (pimples), psoriasis (psoriasis), ichthyosis, lichen planus and other keratinizing diseases. Common A acids on the market include: all-trans retinoic acid, isotretinoin, adapalene, tazarotene, etc., which are divided into two kinds of oral topical application. A acid anti-wrinkle blemish acne effect is stronger, but the irritation is also the largest, need to mention is the use of retinoic acid type of topical drugs and stop using three months after the need for strict contraception. In summary, supramolecular salicylic acid is the three topical acids have the smallest impact on the skin barrier function, and some researchers have found that low concentrations of super-hydrosalicylic acid also have a restorative effect on the skin barrier function (confirmed in animal experiments). Glycolic acid is the most exfoliating of the fruit acids, and it can be used at concentrations up to 70%, which is also arguably the most exfoliating of botryoidal acne. A word of caution is to make sure you do not use high concentrations of fruit acids to brush yourself at home, the consequences can be severe. It is recommended that you fully understand the use and precautions of each acid and use it scientifically under the guidance of a dermatologist.