Fruit acids include malic, tartaric, lactic, citric and glycolic acids. On cosmetic products – both professional and mass consumption – all acids are designated by a special abbreviation AHA, which translates as “alpha-hydroxy acids”.

AHAs (α-hydroxy acids) are one of the most popular ingredients in cosmetic products. They can affect our skin on a molecular, cellular, and tissue level. Simply put, they take care of our epidermis from the outside and inside at the same time. When applied to the skin, the AHAs have an exfoliating, moisturizing, anti-inflammatory and antioxidant effect, as well as stimulating collagen and glycosaminoglycan synthesis in the skin (each acid has a different function).

Types of AHAs:

Glycolic acid is the smallest molecule size of all the alpha hydroxy acids used in cosmetology. It is found in green grapes and sugar cane, the juice of which was traditionally used to whiten skin in South America after it was introduced by Europeans. In addition to its small size, the glycolic acid molecule is also low in acidity, giving it almost limitless opportunities to penetrate the skin. Unlike most other acids, glycolic acid literally falls through the skin, causing an immediate reaction: bright redness, keratin breakdown, exfoliation, decreased production and even an outflow of sebum from those areas that have been treated with the acid.

Glycolic acid gives the full range of common effects of acids: it quickly lowers the pH in the stratum corneum of the skin, which destabilizes the lipids of the skin’s protective mantle and destroys the bonds between cells. It also binds calcium ions, destroying cell bridges and activating the action of enzymes that finally free the cells of the stratum corneum from the bonds between them. The result is a smoother, thinner skin that’s practically instantly visible when high enough concentrations of glycolic acid are used. Of course, with home remedies containing no more than 10-12% acid, it can take days or weeks before visible results are visible, such as the dissolution of comedones.

Glycolic acid directly affects the cells of the deeper skin layers, in particular, it is able to activate the cells of the first, basal layer of the epidermis – a kind of foundation of the surface layer of the skin. With age, the rate of renewal of the epidermis slows down: children’s skin renews on average once every 7-10 days, teenagers renew for 14-20 days, young people renew for 24-28 days. By the age of 40, skin takes 35 to 40 days to renew itself, and then it slows down constantly, going as fast as once every two to three months in old age. Of course, this affects the way your skin looks: new cells form a smoother and more even top layer, they are translucent and may even be slightly opalescent, creating the glow effect of baby and young skin. Older cells that have been dead for a few dozen days look dull, giving the skin a gray and earthy color, creating an uneven texture and an overall impression of calloused and rough skin. Glycolic acid speeds up cell renewal, which can temporarily return the cell renewal cycle to the speed of younger age. The skin quickly becomes fresher, the complexion brighter, and the face gives the impression of a more youthful appearance.

Unlike most other acids, glycolic acid also has the ability to act on the dermis. This effect is called remodeling, because it increases the amount of type I collagen and hyaluronic acid in the dermis. Studies have shown that the higher the concentration and lower the pH of the glycolic acid used, the greater the stimulation of dermal cells will be. This is because glycolic acid irritates the skin at the level of the epidermis, and it is unlikely to penetrate the dermis itself. The cells of the upper skin layer, receptors and free nerve endings begin to send signals that the balance is out of balance and “something is going on upstairs”. This triggers a kind of inflammatory response, a variety of substances are released that trigger protective reactions in the deeper layers of the skin, and the dermis begins to stockpile collagen and hyaluronic acid. In fact, the use of glycolic acid leads to a thinning of the skin’s upper layer, the epidermis, and an increase in the thickness of the lower layer, the dermis. As a result, wrinkles become less noticeable due to the fact that they are smoothed from above and become less deep due to the thinning of the stratum corneum, at the same time they are filled from below due to the counter lift of the deeper layers – the dermis.

Lactic acid – found in sour milk, yogurt, blueberries, passionfruit, maple syrup, apples, tomato juice, grapes. It has a pronounced moisturizing and exfoliating effect (to a lesser extent) and improves skin hydration. Lactic acid is part of the Natural Moisturizing Factor (NFF), a complex of substances with moisture-retaining properties.

Lactic acid belongs to the class of alpha-hydroxy acids (AHA), or as they are also called fruit acids, so its exfoliating ability comes first. However, it is milder and more physiological than glycolic acid, so it can even be recommended for sensitive skin. If the concentration of lactic acid in the preparation meets the standards of safety and efficacy, its positive effect on the skin is very high, while its negative effect on the skin’s protective, barrier and metabolic functions is excluded.

The second thing that must be mentioned about lactic acid is its moisturizing function. At the molecular level, it is part of the skin’s natural moisturizing factor (NMF) and is adjacent to amino acids, urea, pyrrolidonic acid and other components. Lactic acid binds and retains moisture, creating a kind of water shell around itself. And the moisture is not just collected, but also properly redistributed towards the deep, “living” layers of the skin, which creates the effect of balanced hydration in the epidermis.

Another useful property of lactic acid is its ability to strengthen the skin barrier properties by promoting the production of ceramides which, together with cholesterol and fatty acids, form a lipid layer, due to which the skin loses less moisture and better resists the influence of external negative factors. However, the water-saving mechanisms work not only on the surface of the epidermis, but also deep down in the dermis. Lactic acid has a stimulating effect on special cells in this layer of the skin – fibroblasts, resulting in increased synthesis of hyaluronic acid – a substance that actively attracts moisture and acts as a natural filler to maintain skin elasticity. This improves skin elasticity and smoothes out wrinkles.

No less important is the rejuvenating effect produced by lactic acid. It is associated with its ability on the one hand, stimulate fibroblasts in the dermis, thereby creating the conditions for updating the structural elements of this layer, and on the other – to accelerate cell renewal. Traditionally cosmetologists call such action regenerating. As a result, skin quality improves, it becomes more elastic and supple and fine lines are smoothed out.

Special attention should be paid to the bleaching properties of lactic acid, which were widely known since the times of Cleopatra. Residents of Europe and Asia were actively using milk products to remove age spots and improve complexion, because an even tone looks healthy and more attractive.

At present there are two known mechanisms of lactic acid’s action, which leads to skin whitening. The main mechanism is based on exfoliation, when together with keratinized epidermal cells some of the pigment leaves. However, preparations containing lactic acid in high concentrations work differently. They lighten the skin due to their ability to in part block the activity of a special enzyme, tyrosinase, responsible for the formation of the skin pigment melanin. This allows us to fight hyperpigmentation at a deeper level.

A unique property of milk peels is the low photosensitivity, in other words, they increase the sensitivity of the skin to ultraviolet light to the least extent. The size of the molecule of lactic acid is noticeably larger than, for example, glycolic acid, so there is no danger of uneven and deep penetration, and therefore the risk of hyperpigmentation is reduced. This property allows for milk peels even in the spring and summer, which, however, does not negate the need to use protective equipment with ultraviolet filters.

Citric acid – found in many fruits, especially apples and tomatoes. In addition to its exfoliating action, it stimulates cells by increasing cellular metabolism.

Tartaric acid (tartaric acid) – found in free or esterified form in ripe grapes, old wine, oranges. It has exfoliating, whitening and moisturizing effects.

Citric Acid – Found in citrus fruits (lemon, lime, grapefruit, orange, pineapple, papaya and kiwi). It has the highest molecular weight of all the listed AHAs. It has a whitening effect on the skin, which is enhanced in the presence of other acids. It has antioxidant and bactericidal properties, improves cell metabolism and cell renewal, stimulates production of collagen, a substance which gives the skin elasticity and a fresh, healthy look.

In response to increased exfoliation, cell division of the basal layer is activated. In response to increased exfoliation, cell division of the basal layer is activated.

AHAs have a moisturizing effect on the skin due to the accelerated renewal of the epidermis. It is known that on the surface of keratinocytes there is a complex of hygroscopic molecules or NMF (Natural Moisturizing Factor). NMF is most expressed in young cells. In old horny scales NMF is degraded. Accelerated cell division of the basal layer and rapid desquamation of horny scales leads to a higher content of functionally active NMF in the skin.

The increase in the synthesis of glycosaminoglycans and collagen is due to the stimulating action of the ANA on the skin’s fibroblasts. Another explanation of the effect of the ANA on the synthesis of the intercellular substance of the dermis is provided by the stress theory. The chemical action of the ANA on the skin is a stress action which results in the activation of the skin’s defense systems. This leads to mobilization of internal resources, enhancement of reparative activity of skin cells, and increased synthesis of vital molecules.

Thus, under the influence of AHA the epidermis becomes thinner and the dermis thickens. The stratum corneum becomes firmer and more elastic and fine lines on the skin are smoothed out. The application of AHA acids activates cell regeneration, the skin becomes fresher and more elastic. The flow of moisture from the lower layers of the skin to its surface is increased, the skin is moisturized and softened. This is very good for dry skin. Lipid balance is normalized, the sebaceous ducts are cleared, therefore the skin is less greasy, comedones and blackheads are prevented. Hyperpigmented areas of the skin are lightened. In addition, regular removal of dead cells facilitates penetration into the skin active ingredients of creams and serums.

Professional cosmetology is focused on a more pronounced and durable therapeutic result, so the programs use a wide range of enzymes. And in order to achieve the best effect, combinations of enzymes of several types are usually made, for example, from papaya, pineapple and cane, etc. If in cosmetic preparations alpha-hydroxy acids are combined with some other substances, their effectiveness increases noticeably, as the components complement and reinforce each other. For example, vitamins A and E enhance the antioxidant, whitening and toning effect of the acids. The combination of alpha-hydroxy acids and hyaluronic acid guarantees the moisturizing effect and lipid protection. The presence of salicylic acid in the AHA products provides deep cleansing.

THE PECULIARITIES OF THE USE OF COSMETIC PRODUCTS WITH ANA-ACIDS FOR DIFFERENT SKIN TYPES:

Oily skin with a tendency to form acne.The exfoliating effect of AHA (glycolic acid) cleans the sebum ducts, preventing them from clogging and the formation of blackheads. By using AHAs, you are less likely to experience acne scarring. The use of AHAs promotes better skin penetration of the active ingredients in acne treatment products. Fruit acids are not only famous for their exfoliating properties. They are also useful for sebum regulation, for reducing oil production by the sebaceous glands and for dissolving oil plugs, i.e., blackheads.
And, most importantly, using AHAs not only eliminates comedones, but also cleanses the skin deeply. Because through its pores, sweat goes out, and with it all the toxins that enter the body with food, medicine, and from the air. Thus, the detoxification process is greatly accelerated.
Dry skinThe beauty and youthfulness of the skin is directly dependent on its hydration. On the surface of our skin there is a group of hygroscopic substances (amino acids, urea, etc.) that form what is known as NMF (natural mustoraising factor), that is, “natural moisturising factor”. These substances extract water from the surrounding air, absorb it like a sponge, and then moisturize the epidermis from these stores.
As for the fruit acids, they dissolve the skin protein keratogelin to amino acids and thus enhance the hydroscopic properties of our natural moisturizing factor. The thicker the rows of its components, the better it absorbs water.
Thanks to the action of AHAs, old flakes are effectively removed from the surface of the stratum corneum, making it easier for moisturizers to penetrate the skin.
The even exfoliation provided by the AHAs significantly softens rough, dry skin and restores normal skin texture.
Aged skinThanks to the exfoliating effect of the AHAs, the stratum corneum is removed, preventing the penetration of nutrients necessary for regeneration and protection of mature skin.
The AHAs remove the stratum corneum that coarsens the skin and adds wrinkles, and prevent the appearance of lines and wrinkles.
The exfoliation of the dead horny scales stimulates the processes of normal cell regeneration.
The importance of hyaluronic acid is hard to overestimate, because it determines the elasticity of our skin. This substance attracts water and is responsible for the condition of the epidermis, and it is, in fact, the skeleton that holds the intertwined fibers of collagen and elastin. Accordingly, the less hyaluronic acid in the epidermis, the worse we look.
And as we age, its reserves inevitably start to run out. At the same time fruit acids stimulate fibroblasts – the cells of the connective tissue of the body, which are responsible for the production of hyaluronic acid as well as collagen and elastin.
Skin with pyherpigmetationThanks to the exfoliating action of AHAs, surplus horny scales are more effectively removed from the skin surface, making it easier for bleaching medications to penetrate the skin and increase their effectiveness.
In addition to the exfoliating effect, citric and lactic acids have a whitening effect.
By removing dead, hyperpigmented horny scales, AHAs provide a progressive reduction in hyperpigmentation.

WHAT ARE THE PROBLEMS THAT ANA-ACID COSMETICS HAVE TO DO?

Stimulation and cell renewal
Raising skin elasticity
Reducing the depth of wrinkles
Masking skin imperfections
Balance skin color
Moisturizing the skin
Cleaning the skin (destruction of excess sebum and dead cells) in combination with salicylic acid.

The AHA acids can be used for any skin type

The influence of AHA acids depends on many factors, but mainly on the skin type. The beneficial effects of AHA products last for a few days and are gradual: the skin structure and color are improved, the skin feels fresher and softer.

Salicylic acid is a 2-hydroxybenzoic or phenolic acid, C6H4(OH)SON; colorless crystals, well soluble in ethanol, diethyl ether and other polar organic solvents, poorly soluble in water (1.8 g/l at 20°C).
It was isolated from willow bark by Italian chemist Raphael Piria and then synthesized by him.

Main properties of salicylic acid

Deep penetration in the place of application.
Suppression of the activity of sweat and sebaceous glands.
Elimination of the inflammatory process.
Softening of the outer layer of the skin and its gradual discoloration, which leads to an easy separation from the skin surface.
Clearing wounds of purulent secretions and stopping the spread of pathogenic bacteria.
Acceleration of the healing process, due to increased blood flow to this area of the skin.

Effective drug for:

hyperhidrosis and hyperkeratosacne
and postacne;
warts;
corns and calluses;
black spots;
eczema;
infectious skin diseases;
inflammation on the skin.

Contraindications to use:

Hypersensitivity;
very dry skin;
renal insufficiency;
pregnant and lactating;
prohibited for children under 3 years of age.

Citric acid is a natural substance found mainly in all types of citrus fruits.
In its original form, citric acid is very often used to adjust the pH of cosmetic products, mostly skin care products. Adding this ingredient to a cosmetic formula makes the product more acidic, which optimizes its function as well as further preserving the product. However, this is not the only function of this ingredient, although it is the most sought after.

Citric acid is a member of the alpha-oxy acid family of molecules, a class of compounds commonly used in skin care products that are designed to exfoliate (exfoliate) facial skin. When applied to the skin in a sufficiently concentrated dose, citric acid breaks the protein bonds between “dead” and “living” epidermal cells, resulting in old, dead cells being easily removed, leaving skin clean and smooth and glowing. Alpha-hydroxy acids, including citric acid, are also used as active ingredients in home and clinical chemical peels: they are designed to refresh the complexion, remove fine lines, superficial scars and areas of discoloration (hypo- or hyperpigmentation). By removing keratinized cells that often clog pores, citric acid is very useful for people who suffer from acne or enlarged pores. When applied topically to the skin, citric acid also acts as an antioxidant to help reverse the signs of aging.

Benzoic Acid (benzoic acid) is one of the strongest preservatives, it prevents mold fungi, yeast, slows oxidative reactions, and inhibits the activity of enzymes that break down fats and starches. It has antimicrobial and antifungal effects.
For cosmetic purposes C7H6O2 is almost always produced synthetically. The main role of the additive is as a preservative, to inhibit bacterial growth, to increase the shelf life of the product. If we talk about which cosmetic products use benzoic acid, the first thing you should pay attention to are creams, lotions and scrubs for problem skin. Having the property of actively fighting microbes, acid in the composition of these cosmetics will help get rid of pimples and redness on the face and other parts of the body. It is also used to whiten skin, remove age spots and freckles.

Azelaic acid is a phyto compound of cereal plants such as wheat, rye and barley. Azelaic acid is formed during lipid metabolism and is found in small amounts in the human body. For cosmetic and pharmaceutical purposes it is obtained biochemically.
Its action on the skin is antioxidant, bactericidal, keratolytic, bleaching, purifying, anti-inflammatory. In cosmetics, azelaic acid is very effective in treating the symptoms of a number of inflammatory skin conditions. In the West, for the most part, azelaic acid is recommended as a cosmetic or medicinal ingredient for treating acne. However, many studies have demonstrated its efficacy in combating hyperpigmentation when used topically.
Effects of azelaic acid

First of all, azelaic acid has a strong antimicrobial effect, so it is also widely used in the treatment of acne. Azelaic acid, once applied, kills propionic bacteria on the skin and thus helps to cleanse it of acne pathogens and prevent the formation of new acne. Azelaic acid is good for mild to moderate acne, but of course it is not very good for non-bacterial acne.

Azelaic acid also acts as an antioxidant in cosmetics, so it has a pronounced anti-inflammatory effect – red spots after acne disappear under its effects. American dermatologists also often prescribe it to reduce the redness that accompanies another inflammatory skin condition, rosacea.

The ability of azelaic acid to lighten skin has been proven by research and years of use, although scientific studies have not been able to show exactly how this ingredient works to lighten age spots of varying natures (melanoderma, chloasma, etc.). Today it is believed that azelaic acid interrupts the biochemical processes that contribute to the synthesis of melanin pigment and thus helps to achieve a skin lightening effect.

Kojic acid is a fermentation byproduct derived from glucose during the fermentation of rice by yeast-like fungi. It is classified as a natural whitening active ingredient and has been used relatively recently in cosmetics since 1989.

How does kojic acid work:

it blocks the tyrosinase enzyme in melanocytes. The main causes of the appearance of age spots:

Impaired metabolism.
Liver disorders.
Changes in hormonal background due to pregnancy, puberty.
Skin diseases, such as seborrhea, acne, etc.
Stress.
Antibiotics.
Ultraviolet light from frequent exposure to the sun or tanning beds.
The aging process.
Disruption of the gastrointestinal tract.

Kojic acid is quite effective for bleaching pigment spots of any etiology.

The properties of kojic acid:

skin whitening, lightening of pigment spots, freckles. Kojic acid as a bleaching agent is effective for all types of pigmentation disorders listed above.
kojic acid is an antioxidant. It blocks the effects of free radicals on skin cells and slows down the aging process.
antibacterial and antifungal. Kojic acid blocks the processes of division of bacteria and fungi, promotes faster healing of inflammations.

Phytic acid in its pure form looks like a white amorphous powder without a distinct smell or taste. It is obtained in the laboratory and in production by treating phytin-containing plant parts. It is found in the germinated grains of cereals, pulses, some vegetables, oil crops, as well as in the brain tissue and kidneys of mammals and humans. In medicine, phytic acid is an intermediate in the synthesis of some drugs that help with diseases of the nervous system and liver.

It has been found that phytic acid, along with its deep and very mild cleansing and exfoliating effect, is capable of inactivating the enzyme tyrosinase, the excessive production of which leads to hyperpigmentation. This is determined by the high antioxidant, brightening and anti-inflammatory properties of phytic acid, which contributes not only to the effective prevention of pigment spots, but also the rapid removal of existing ones. And also phytic acid has a good rejuvenating and lifting action. Among the distinctive features of phytic acid is the fact that even at a high concentration of 50% and a low pH of 1.2 it is not able to cause damage to the deep epidermal layers. This predetermines the rapid effect of this acid on the skin with complete absence of pain and discomfort. Phytic acid molecules are very large, so when treating the skin they do not penetrate deep into the skin, but remain in the stratum corneum. At the same time they are able to retain hydrogen ions, preventing their penetration into the skin. With prolonged (more than 15 minutes) exposure of phytic acid to the skin the process of keratinocytes destruction begins, so this period is the maximum possible exposure.

Preliminary studies conducted by Israeli dermatologists allow to claim that phytic acid preparations have pronounced anticancer properties expressed in:

inhibition of cell division;
in enhancement of apoptosis (cell suicide);
inhibition of vascular growth;
in binding divalent zinc and copper cations, which entails lack of these elements, urgently required for skin health;
in exhibiting pronounced antioxidant properties. Thus, at present, the scientific community speaks of phytic acid as an insufficiently studied substance that exhibits ambiguous biological activity.

What are fruit acids and how are they labeled?