Lactic acid is the most widely occurring acid in nature. In the form of lactate it is a normal ...
Lactic acid, in the form of lactate, is an important intermediate product of the human metabolic process, for instance as a product of the breakdown of sugar as a result of lactic acid fermentation.
In view of their optical chirality, D-(–)-lactic acid [alternatively, (R) lactic acid] is referred to as levorotatory lactic acid, and L – (+) – lactic acid [alternatively, (S) lactic acid] as dextrorotatory lactic acid.
L-(+)-lactic acid is present in sweat, in blood in muscular serum and the kidneys, as well as bile and saliva. The racemic mixture (i.e., a 1:1 mixture of D and L-forms of lactic acid), occurs in dairy products, tomato juice and beer. Fungi also produce lactic acid.
A range of foodstuffs is produced as a direct result of lactic acid fermentation. These include dairy products such as curdled milk, yoghurt, kefir and buttermilk. Other products include lacto-fermented vegetables, such as sauerkraut, borscht and kimchi, as well as sourdough and sourdough products. Silage, which is fresh animal feed preserved through fermentation, is produced as a result of the presence of lactic acid.
When used as a dietary supplement, lactic acid is designated as E270. It is used widely throughout the food and beverage industries, including in the production of baked goods and confectionery, and occasionally in soft drinks. Changing the pH of a foodstuff to a value of 4 or similar causes the food to be preserved as colonization by other microorganisms is largely prevented.
Physician, Dr. Dieter Thierbach, refers to the dextrorotatory form of lactic acid as a natural intermediate product of metabolism. It is quickly and comprehensively broken down in the body by a specific enzyme, L-lactate dehydrogenase.
In a physiological context, dextrorotatory S and L-(+)-lactic acid is formed in sufficient quantities as a result of the presence of glucose in all healthy muscles, organs and erythrocytes. Every human heart is dependent on the constant presence and supply of dextrorotatory (S)-lactic acid to regulate cardiac and circulatory functions. Lactic acid can be broken down in the liver, and around 60% of all lactic acid expended in daily life is converted back in to glucose and glycogen there.
Pharmaceutical technology makes use of lactic acid to convert water insoluble drugs into salts of lactic acids (lactates), which then dissolve more effectively in water.
In the cosmetic industry, lactic acid is used in skin creams and other products used in treating acne. 8%-lactic acid is referred to as Natural Moisturizing Factor (NMF): this creates a hydroscopic film over the epidermis, which has a moisturizing effect on the stratum corneum. Lactic acid also regulates the skin’s physiological pH value as a component of the skin’s own protective acidic layer and thus prevents bacterial colonization of the skin. In low doses, lactic acid reduces the cohesion of the corneocytes of the stratum corneum (the uppermost layer of the epidermis in humans), loosening intercellular connections and thus regulating keratinization. This causes the stratum corneum to become thinner and more flexible, which assists in treating skin conditions such as blemishes, acne, psoriasis and ichthyosis.
Occasionally, the question is raised as to whether lactic acid acts is caustic, or whether it is an irritant.
A substance is caustic if it destroys living tissue upon contact, while it is an irritant if it can cause inflammation as a result of short-term, longer-term or repeated contact with the skin or mucous membranes without having a corrosive effect.
In a study carried out by the Ministry of Labor, Integration and Social Affairs of the German Federal State of North Rhine-Westphalia, investigating the question of when lactic acid should be categorized as caustic or an irritant. At Skinial, we received a response dated November 16th, 2011 to the effect that, according to the GESTIS Materials Database of the relevant professional bodies, lactic acid can cause severe damage to the eyes and can irritate the skin. However, it was not assessed as caustic or corrosive.
In order to place the word “irritant” into a more realistic context, the document “Basic environmental knowledge for vocational schooling around everyday chemistry,” the following everyday products are given the following assessments:
Skinial uses a weak solution of dextrorotatory lactic acid, as found in the human body, as a tattoo removal product in quantities of 0.04 ml per dot (covering a maximum area of 0.5 cm × 0.8 cm). The quantity used is the equivalent of a small droplet, and the concentration is reduced further by bodily fluids before it reaches the active area of the skin. It is precisely the extremely small quantity in which the active ingredient is used that distinguishes Skinial from other cosmetic applications of lactic acid.
Additionally, it can be asserted that lactic acid is a substance present in human physiology that is required for human life, and which the body continually makes and then breaks down again. It impossible to conceive a more natural substance to be used in the tattoo removal process.
There are, however, significantly different substances available that are seen as wholly unremarkable by the cosmetics industry as a whole and which, in an appropriate dose, help patients achieve a younger appearance even though a dose of just one to two micrograms can be fatal to adults. That product is the botulinum toxin, also known as Botox. It is produced by bacterial cultures that grow in spoiled, canned foods that are poisonous when ingested and, in fact, it is the most dangerous neurotoxin in the world.
However, as Paracelsus himself said as far back as 1585: “Nothing is free of poison. The only thing that stops anything from being a poison, is the dosage.”