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Introduction Glossary - Index

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An antioxidant is a substance capable of neutralizing or reducing the damage caused by free radicals, toxic molecules to the body that can accelerate skin ageing.

They are naturally present in the body and can be supplied in the diet. Vitamins A, C and E are among the antioxidants that are often found in the composition of anti-ageing treatments. To learn more about antioxidants, you can consult our report on oxidative stress and our tips to enjoy the anti-ageing properties of food.


Collagen is a fibrous protein that helps give skin its strength. It is produced by fibroblasts cells that represent the largest portion of the connective tissue (liaison and support between different tissues and organs).

Collagen in cosmetics is used to restore volume to the face and thus reduce the signs of skin ageing.


Cortisol is a hormone produced from cholesterol by the adrenal glands. It is involved in the balance of blood glucose and the release of sugar from the body reserves to meet heightened demand for energy, for example during a stressful situation.

Cortisol also has an impact on the regulation of sleep, and consequently, the process of cell regeneration. At its maximum between 6 and 8 am, its secretion decreases until evening.

To learn more about the role of cortisol in ageing skin, you can view our report on stress.


Dermabrasion is a technique to scrape off the surface layers of the skin (epidermis and dermis), which erases scars, wrinkles, tattoos and sometimes performed, under local or general anesthesia, with a rapidly rotating wire brush.

To learn more about this technique, check out our report on dermabrasion.


The dermis is one of the three layers of the skin located between the epidermis (the outermost layer of the skin) and hypodermis (the deepest skin layer). It protects the subcutaneous regions and controls the heat loss from the body. It also provides nutrition to the epidermis.

It comprises:

  • Fibroblasts, which produce the fibers which are destroyed progressively as they age;
  • Collagen, which gives the skin its firmness and strength;
  • Elastin, which gives it its elasticity;
  • Water;
  • Protein;
  • Cells and connective tissue fibers (linking the different tissues and organs).

To learn more about the skin and how it works, you can visit our special report on the structure of the skin.


DNA is the abbreviation used to refer deoxyribonucleic acid, an essential component of chromosomes that contains the hereditary information of each individual.

It is from DNA that cells get the information they need to function properly. This pattern is disrupted when the structure of DNA is altered, for example by sun ultraviolet rays. Mutations can then occur, with consequences ranging, in the most severe cases, from the acceleration of skin ageing to the increase in the risk of developing skin cancer.

To learn more about the action of sun on the skin cells’ DNA, you can consult our report on the effects of sun on the skin. If you are looking for advice to avoid skin alterations by UV rays, you can find our tips to take care of your sun-exposed skin.


Elastin is a protein used in the formation of tissues and organs. Elastin molecules allow the connective tissue to be stronger and more elastic. Over time, the body produces less elastin, making the skin thinner and leading to the acceleration of the appearance of wrinkles.

Free radicals produced by UV rays, by attacking the cells, contribute to the decrease in the production of elastin.

To learn more on this topic, you can read our report on the sun and skin ageing, and our tips to protect yourself from the harmful effects of the sun.


Superficial layer of the skin, the epidermis protects the dermis and the whole body from the outside thanks to its impermeability, strength and flexibility. Whilst the keratin it contains protects us from physical aggressions (wind, sun, humidity and drought ...) and chemical aggressions (such as pollution), Langerhans cells preserve our immunity.

The epidermis itself is composed of several layers where we can find melanocytes in particular, the cells at the origin of tanning. It is crossed by channels of sweat glands (those that produce sweat) and the sebaceous follicles, which contain the root hairs and from where the sebum is drained off.

The superficial layer of the epidermis, very rich in keratin, is called the stratum corneum. This is where the dead skin cells are eliminated, through desquamation.

To learn more about the skin and how it works, visit our special report on the structure of the skin.

Fatty acids

Issued from the degradation by the digestive system of dietary lipids, fatty acids are an essential source of energy for the body. More than 40 different types of fatty acids exist and they are classified into different families according to their chemical composition. We distinguish:

  • Saturated fatty acids, usually solid at room temperature (butter, cheese, meats, palm oil ...)
  • Unsaturated fatty acids, subdivided themselves in monounsaturated fatty acids (olive, canola and peanut, nuts ...) and polyunsaturated fatty acids (fatty fish, vegetable oils, eggs ...).

Some lipids contain several kinds of fatty acids. Rapeseed oil for example includes both monounsaturated fatty acids and polyunsaturated fatty acids.

To find out which of these fatty acids are recommended to preserve your skin’s youthful appearance, you can read our report on Nutrition and our tips to take care of your skin thanks to diet.


Cells in the form of rockets or stars, known as fibroblasts come from the connective tissue cells of the skin (connective tissue cells form the filling and supporting tissues of the body). They produce collagen and elastin, two substances that provide skin strength and suppleness and play an important role in repairing cutaneous lesions.

Free radicals

Chemically unstable molecules produced by the body, free radicals are toxic for living beings.

Free radicals come from radiations that produce energy (like UV rays) and are mainly synthesized in the cells during biochemical reactions with oxygen.

To understand the process behind the formation of free radicals, you can check our report on oxidative stress. Our report Understanding skin ageing also contains many explanations of this phenomenon. Finally, find our advice to fight against free radicals in our section Beauty Coaching.


As a chemical reaction taking place in the heart of the dermis, glycation, is triggered when there is a high concentration of sugar in the blood: glucose molecules from the diet react with protein molecular structures and in result a disruption of the dermis.

This phenomenon causes damage to the cells, tissues and blood vessels- resulting in accelerated skin ageing.

To learn how to limit it, do not hesitate to consult our dossier explaining the link between nutrition and skin ageing.


Substance produced by a so-called endocrine gland, a hormone is released into the blood and acts specifically on a targeted organ or tissue in order to modify its functioning.

Transmitter of chemical messages, the hormone stimulates or inhibits the functioning of its receptor.

To find out which hormones are involved in skin aging, check out our reports Stress and ageing and Sleep and ageing.

Hyaluronic acid

Hyaluronic acid is a molecule consisting of a combination of sugars. It occurs naturally in the body, particularly in the connective tissue and other biological fluids to which it provides viscosity.

In the skin, the hyaluronic acid fills the intercellular space and contributes to the hydration and to the cohesion of the tissues. It is used in cosmetics for its moisturizing properties and as a filler treatment in aesthetic medicine.

For more information, check out our complementary information on hyaluronic acid and our report on hyaluronic acid injections.


The deepest layer of the skin, the hypodermis is mainly composed of fatty tissues.

The hypodermis is traversed by blood vessels and contains sweat glands, and the roots of the longer bristles.

To learn more about the skin and how it works, you can read our report on the structure of the skin.


Keratin is a protein whose main qualities are its strength and its suppleness. Produced by cells called keratinocytes, it is found in the hair, eyelashes, hair and nails, but also in the superficial layer of the epidermis it protects against external aggressions and to whom it gives logically resistance and suppleness.

For further reading, you can consult our reports on skin structure and on the sun spots. Indeed, some spots are sometimes keratosis due to excessive sun exposure.


Although “laser” is used as a noun, it is an acronym for Light Amplification by Stimulated Emission of Radiation. During a laser procedure, a device produces a narrow beam of light radiation able to alter the structure of the skin target on which it is projected. It can thus alter a very specific area, leaving the surrounding tissue intact. It is used in aesthetic medicine for hair removal, treatment of wrinkles and skin imperfections.

You can read more about it by visiting our page dedicated to laser procedures in aesthetic dermatology.


Melanin is a dark pigment produced by cells called melanocytes.

They are found in the skin, hair and the membranes of the eye. Its role is to protect the skin against the sun’s ultraviolet radiation that accelerates skin ageing and increase the risk of developing skin cancer.

These are heredity and hormonal stimulation of melanocytes that determine the amount of melanin present for an individual.

For more information, consult our reports on the effects of sun on the skin’s melanin production and sun spots.


Melanocytes are cells which are found mainly in the epidermis and dermis. Their role is to synthesize melanin, a pigment that gives color to the skin, hair and eyes, and protects us (in part) against the harmful effects of ultraviolet rays. This phenomenon is called melanogenesis.

To learn more about the effects of the sun melanocytes and melanin production, take a look at our page dedicated to sun spots.


Natural hormone produced by the pineal gland, melatonin helps to control to the rhythms asleep /awaken stages. It's called “sleep hormone” because it is indeed this hormone that pushes us to fall asleep.

Its secretion increases shortly after nightfall. The level of melatonin peaks between 2am and 4am and then decreases.

To find out how melatonin can be considered as an anti-ageing hormone, do not hesitate to consult our report on sleep and skin ageing.


Mesotherapy is a technique that involves injecting substances into the skin or drugs at small doses. This mode of administration helps strengthen and prolong the action of these substances.

Injections, performed using a syringe, are for example used in aesthetic medicine.


The term microcirculation refers to the blood flow of vessels of less than 50 microns in diameter. Organized under an independent and larger network of blood vessels, they irrigate more particularly the skin, the mucous membranes and the soft tissues (adipose tissue, connective tissue, muscles).

Microcirculation is fundamental because it brings blood to the cells, and therefore the necessary nutrients and oxygen cells need so as to function properly.

More active at night, it then allows the acceleration of cell renewal. Therefore, lack of sleep limits cell renewal with a visible immediate effect: a dull complexion.


Nutrients are food compounds that come from food and that are used by the body to function.

One distinguishes nutrients that provide energy (proteins, carbohydrates, lipids and alcohol) of those which ensure a constructive or protective role (minerals, vitamins, water, but also proteins).

To learn more about the role of nutrients in skin’s health and youthfulness, check out our special report on nutrition and its effects on the skin. To find all our recommendations, you can read our coaching section on anti-ageing nutrition.


Polyunsaturated fatty acids play a role in the structure of the nervous system. Omega-3 fatty acids are essential because the body cannot synthesize them. It is therefore important to provide it through food. Foods containing omega-3 are mainly fatty fishes (tuna, mackerel, sardines, herring ...) but also rapeseed, soybean, flaxseed and walnut oils.

For more information, find our report on nutrition and its effects on the skin.


A poly-unsaturated fatty acid that has a preventive role in inflammatory processes. Like Omega-3, Omega-6 fatty acids are essential because the body does not know how to synthesize them alone: they are found in oleaginous fruits and vegetable oils (rapeseed, sunflower, nuts, corn, grape seed, borage, evening primrose).

For more information, find our report on nutrition and its effects on the skin.


Peeling is a technique in aesthetic medicine to regenerate facial skin using a chemical process of destruction of the superficial layers of the skin.

Substances used to achieve exfoliation determine the type of peel, which can be superficial, medium or deep. This process helps to reduce the appearance of acne marks or reduce the appearance of signs of ageing such as fine lines.


Also known as "vitamin A", retinol is a fat soluble vitamin which plays an important role in vision (more particularly in night vision). It contributes to the growth of bone, to regulate the immune system, to reproduction, but also to the health of the skin and of the mucous membranes. It seems that vitamin A also protects the cell metabolism against oxidation. These two effects explain why it is used in many anti-ageing cosmetics.

We can find vitamin A in certain foodstuffs of animal origin (liver, eggs, oily fish, milk and milk products not skim) but also in fruits and vegetables containing carotenoids, recognizable by their green, yellow or orange colors.


Sebum is a mixture of fatty substances specific to human beings and produced by the sebaceous glands. Sebum contains lipids, fatty acids mixed together with skin and hair detritus, as well as waxes (such as cerumen). Mingled with sweat and skin debris, it forms a hydro-lipid film that covers the epidermis, the most superficial layer of the skin, and protects it from external aggressions (bacteria, mushrooms, humidity, drought ...) whilst maintaining it suppleness.

When sebum is produced excessively, the skin is called "oily". Find all our tips and explanations in our report dedicated to oily skin.

Ultraviolet rays  

Electromagnetic radiation invisible to the human eye, ultraviolet rays, or UV rays, come in particular from the sun.

Ultraviolet rays get their name from their position: just after the purple band of the visible spectrum of light.

There are:

  • Ultraviolet A (UVA), of long wavelength, responsible for tanning and synthesis of vitamin D, but also for skin ageing and the formation of degenerative skin lesions.
  • Ultraviolet B (UVB), of medium wavelength, causing sunburn and burns during unprotected sun exposure.

Vitamin D   

Vitamin D is a vitamin that we need to absorb calcium and fix the bones. It also takes part in other biological phenomena like immunity.

The body synthesizes vitamin D thanks to UV radiation, by transforming cholesterol. Vitamin D can also be provided by food (plant and animal products).

Take Your Skin Diagnostic

Take Your Skin Diagnostic

Adopt a new lifestyle

Adopt a new lifestyle