Epidermis

The epidermis is the outermost layer with different thickness at different sites. It is thinnest on the eyelids with only about 0.1mm, and, because of the need to sustain constant friction, is thickest on the soles of the feet and the palms of the hands, with about 0.7mm, which is about 3 –4 sheets of paper.

The epidermis consists of three interwoven types of cells:

  • Keratinocytes, which make the protein keratin;
  • Melanocytes, which produces the sun-tanning pigment melanin (which protects us from ultraviolet radiation and determines your skin color);
  • Langerhans cells, which are part of the immune system and intercept foreign substances that try to pass through the skin.

Growth Cycle of the Keratinocytes

They are the main cells forming the epidermis, accounting for about 80-90% of the cell population. They split at the bottom layer of the epidermis and migrate upwards, mature in the process and die off, forming the outer layer of dead, hard, tough cells that form the hard skin surface called the Stratum Corneum, which shed off at the end.

This process normally happens with sequences. Newly formed keratinocytes will replace those shed off at the top. The whole cycle takes about 40 days, and is particularly important for the healthy skin. Aged skin has a slower growth cycle, and this results in thick and rough skin.

Effective skin care products can normalise this cycle, thereby forming a thin and soft Stratum Corneum.

The keratincytes have different look when they are migrating upwards. They can be divided into 5 layers:

  1. Basal Cell Layer - It produces millions of new cells at the bottom of the epidermis every day.
  2. Stratum Spinosum
  3. Stratum Granulosum
  4. Stratum Lucidum
  5. Stratum Corneum

Stratum Corneum

It consists of piled up flat, dead and tough keratinocytes, basically a protein we call Keratin. Older people have thicker layers with about 17 cells thickness, whereas younger people have about 12. The cells are drier when nearer the surface, and too thick a layer will make the skin look dull. Some skin care products can moisturise this layer and make it thinner again, improving the tone.

The main function of this layer is to withstand damages from constant friction. Between them there is the Intercellular Lipid, which passes through the cells to the surface. It also helps the cells to stick together tightly to act as a barrier as well as prevent water loss. The quantity of this intercellular lipid will affect the water content in the Stratum Corneum. Another factor, the Natural Moisturising Factor, also affect the water holding capacity and therefore the water content.

When the skin ages, these two factors will decrease, and so the water content will drop. Researches show that the water content is about 75% when we are born, 70% when we are children, and only 60% when we are adults.

Connection with the Melanocytes

The melanocytes scattered amount the keratinocyts, mainly in the Basal Layer, at the border of the epidermis and dermis. Inside the melanocytes are structures called the Melanosomes, which are the factories for making Melanin. Melanin is passed through the connections to the surrounding keratinocytes, protecting them from the damages of the ultraviolet light, as well as absorbing and filtering excessive ultraviolet light so that less can penetrate into the deeper level to cause damages. When stimulated by ultraviolet light, its production escalates many folds and results in a darker skin complexion.

The number of melanocytes in different races is actually the same. It is the amount of Melanin that determine the skin colour. In black skin type, the melanosomes are larger and denser, with lager amount of melanin. The opposite holds for the white skin type.

When the melanocytes are not functioning right, many problems such as over pigmentation or uneven skin tone will arise. Sun, skin inflammation, hormonal changes can all interfere with the melanocytes metabolism and function. Some skin care products can effectively correct this by decreasing the production of melanin inside the melanocytes.

The Origin of Skin Allergy

The Langerhans cells act as the guard in the skin’s immune system. They look for foreign materials (Antigen) and pass them over to the lymph cells, which will start a whole cascade of rejection reactions. This is the basis of allergic contact dermatitis.

The trends of skin care products have moved to include different medical ingredients. Many skin care brands develop separate lines in this direction, emphasizing the medical science behind and the superiority of them over the traditional skin care products.

The concept of healthy skin and anti-aging has revolutionized the market and slowly replace the tradition concept of skin care. This is more like a treatment, and aims to target the skin actively and totally from inside out, rather than dealing with just one single skin problem.

These medical ingredients will improve and stimulate the skin cell regeneration, stimulate the production of collagen and elastic fibres, as well as remove harmful free radicals, prevent and reverse the aging process.

These products are very often customized to individual needs, under the care and supervision of the physicians, so that it can maximize the clinical benefits, in people of different age groups, with different skin types and skin problems. Apart from the face, they can be used anywhere else on the body including the neck, chest, backs and hands.

Note: Since there are just too numerous ingredients, it is impossible to list all of them here, but we have tried to include most of the commonly seen ingredients, which you may encounter in your skin care products.

Ingredients Functions
 
A
Alfalfa Oil Used in sunscreen to prevent sunburn
Alkyl Benzoate Moisturise
Allantoin Soothing effect
Aloe Vera Hold moisture; dissolve dead skin cells; anti-inflammatory; promote cell and wound healing
A|pha Lipoic Acid Anti-oxidant property
A|pha Tocopherol Anti-oxidant property
Aluminum Chlorohydrate Absorb water and keep skin dry, used in anti-perspirant
Apricot Kernel Oil Contain vitamin A & E. Moisturise and soften skin; keep skin firm
Arbutin Block melanin formation, whitening effect
Avocado Oil Contain unsaturated fatty acid, plant cholesterol, vitamin A & E. Moisturise and soften skin
Azelaic Acid Block melanin formation, whitening effect; anti-inflammatory, anti-bacterial, used to treat acne
 
B
Babassuamidopropylamine Foam enhancer
Bees Wax Increase skin softness and elasticity; anti-microbial & increase thickness of skin products
Bentonite Natural earth
Benzalkonium Chloride Anti-microbial, preservative property
Benzophenone Absorb UV radiation, mainly UVA, used in sunscreen, can cause skin allergy
Benzyl Alcohol Anti-microbial, preservative property
Benzoyl Peroxide Anti-microbial, anti-inflammatory
Borage Oil Contain high content of linoleic acid, moisturize & improve roughness
Butyl Methoxydibenzoylmethane Absorb UV radiation, sunscreen
Butylparaben Anti-microbial, preservative property
 
C
Candelilla Wax Increase thickness of skin products
Caprylic / Capric Triglvceride Moisturise & increase smoothness
Carbomer Increase thickness of skin products
Carnuba Increase thickness of skin products
Castor Oil Contain ricinoleic acid, moisturise
Ceresin Emulsifier
Ceryl Alcohol Emulsifier, no special effect, may irritate skin
Ceteareth-12 , ceteareth-20 Emulsifier; moisturise
Cetearyl Alcohol Emulsifier
Cetyl Acetate Increase thickness of skin products
Cetyl Alcohol Emulsifier, no special effect, may irritate skin
Cetyl Dimethicone Moisturise & increase smoothness
Chamomile Anti-microbial, anti-inflammatory
Cholesterol Emulsifier; moisturise
Citric Acid Preservative; balance acidic / alkaline status
Citric Alcohol Emulsifier
Citric Oil Moisturise
Cocamidopropyl Betaine Emulsifier; foam enhance; moisturise
Cocamidopropyl Hydroxy Sultane Surfactant, remove oil
Coconut Diethanolamide Emulsifier; form enhancer
Cyclomethicone Moisturise & increase smoothness
   
D
Dead Sea Salt Extract Anti-aging; whitening effect
Diazolidinyl Urea Preservative
Dimethicone Moisturise & increase smoothness
Dimethicone Copolyol Moisturise & increase smoothness
Dimonium Chloride Phosphate Essential fatty acid, remove oil, emulsifier
Dioxybenzone Absorb UV radiation, used in sunscreen
Disodium EDTA Preservative
Disodium Laureth Sulfosuccinate Surfactant, foam inducer
   
E
Erucamidopropyl Hydroxy Sultane Form enhancer
Evening Promose Oil Contain linoleic acid, moisturize and soften skin
Ethylparaben Preservative
   
F
Fatty Alcohol Ether Sulfates Emulsifier
   
G
Germaben ll Preservative
Glycerin Moisturise & increase smoothness
Glyceryl Ricinoleatec Moisturise & increase smoothness
Glyceryl Stearate Emulsifier
Glyceryl Cocoate Emulsifier
Glycolic Acid A fruit acid, remove dead skin; stimulate collagen; whitening effect
Green Tea Extract Anti-oxidant
   
H
Hyaluronic Acid Absorb and hold moisture
Hybird Safflower Oil Stabliser
Hydrogenated Soy Glyceride Moisturise
Hydrolyzed Whole Wheat Protein Water soluble protein, hold moisture; sooth irritation; anti-aging
Hydroquinone Inhibit melanin formation, decrease pigmentation
Hydroxvpropyl Methylcellulose Preservative
Hydroxybenzoate Moisturise & increase smoothness
   
I
Imidazolidinyl Urea Preservative
Isopropyl Alcohol Emulsifier
Isopropy| Myristate Reduce oiliness of skin product; ingredients blender; moisturise and soften skin
Isopropyl Palmitate Reduce oiliness of skin product; ingredients blender; moisturise and soften skin
Isostearoyl Hydrolyzed Collagen Moisturise
Isostearic Acid Adjust thickness and texture of skin product
Isostearyl Alcohol Emulsifier, no special effect, may irritate skin
   
J
Jojoba Oil Moisturise, non-greasy
   
K
Kojic Acid Inhibit melanin formation, whitening effect; anti-microbial
Kukui Nut Oil Non-greasy, penetrate well, moisturise and soften skin
   
L
Lactic Acid A fruit acid, remove dead skin; stimulate collagen; whitening effect
Lanolin Alcohol Emulsifier
Lauryl Betaine Surfactant, strong foam inducer
Lauryl Diethanolamide Surfactant, foam inducer
L-Ascorbic acid Active form of vitamin C
Linoleamidopropyl PG- Essential fatty acid, moisturise
Linoleic Acid Unsaturated fatty acid, prevent moisture loss; soften skin; help skin regeneration
Liquid Paraffin Moisturise & increase smoothness
   
M
Macadamia Nut Oil Contain palmitoletic acid, protect cell wall; moiturise
Malic Acid Apple acid, remove dead skin; stimulate collagen; whitening effect
Magnesium Aluminum Silicate Increase thickness of skin products
Menaquinones Prevent and dissolve bruises
Methyl Anthranilate Absorb UV radiation, mainly UVA, used in sunscreen
Methyl Hydroxybenzoate Moisturise & increase smoothness
Methylparaben Preservative
Mineral Oil Moisturise & increase smoothness
Myricyl Alcohol Emulsifier, no special effect, may irritate skin
   
O
Octyl dimethy PABA Absorb UV radiation, used in sunscreen, may cause allergy and cancers, now banned
Octyl Methoxycinnamate Absorb UV radiation, used in sunscreen
Octyl Salicylate Absorb UV radiation, used in sunscreen
Oleic Acid Unsaturated fatty acid, prevent moisture loss; low irritation; used as base in sunscreens
Olive Oil Unsaturated fatty acid, prevent moisture loss; soften skin; help skin regeneration
Oxybenzone A fruit acid, remove dead skin; stimulate collagen; whitening effect
Ozokerile Increase thickness of skin products
   
P
Palmitoleic Acid Unsaturated fatty acid, prevent moisture loss; soften skin; help skin regeneration
Para Amino Benzoic Acid (PABA) Absorb UV radiation, used in sunscreen, may cause allergy and cancers, now banned
Paraffin Increase thickness of skin products
Petroleum Moisturise & increase smoothness
Polybutene Increase thickness of skin product
PPG-11 Steryl Ether Moisturise & increase smoothness
Propyl allate Preservative
Propyl Hydroxybenzoate Moisturise & increase smoothness
Propylene Glycol Absorb moisture; help to blend ingredients; preservative
Propylparaben Preservative
   
R
Retinoids Vitamin A derivative, normalise keratinocytes growth; reduce pimples; anti-aging
Retinyl Palmitate Vitamin A derivative, normalise keratinocytes growth; reduce pimples; anti-aging
Rose Hips Contain high content of vitamin C, anti-oxidant
   
S
Safflower Oil Moisturize & increase smoothness
Salicylic Acid Soften surface dead cells; remove roughness; stimulate collagen
Sasame Oil Smoothen texture of skin product
Silica Reflect UV radiation, used in sunscreen
Silk Amino Acid Moisturise
Sodium Ascorbate Vitamin C derivative, anti-oxidant
Sodium Cocoate Surfactant
Sodium Cocoyl Sarcosinate Surfactant
Sodium Citrate Emulsifier
Sodium Hydroxymethylglycinate Emulsifier
Sodium Lauryl Sulfate Surfactant; emulsifier; strong foam inducer
Sorbic Acid Preservative
Sorbitan Oleate Moisturize & increase smoothness
Sorbitol Absorb and hold moisture
Soy Protein Water soluable protein, moisturize and sooth irritation; anti-aging
Squalene Enhance skin cell metabolism
Stearic Acid Saturated fatty acid, adjust thickness and texture of skin product
Stearyl Alcohol Emulsifier, no special, may irritate skin
Stearyldimonium Hydroxypropyl Oxyethyl Cellulose Highly effective moisturiser
   
T
Tetrasodium EDTA Preservative
Titanium Dioxide Reflect UV radiation, used in sunscreen
Tocopheryl Acetate Active form of Vitamin E, anti-oxidant
Trideceth-7 Carboxylic Acid Foam enhancer
Triethanolamine Adjust acidic / alkaline balance
   
U
Urea Moisturise & increase smoothness
   
V
Vitamin E Acetate Anti-aging, anti-oxidant
   
W
Wax Esters Moisturise & increase smoothness
Wheat Germ Oil Moisturise & increase smoothness
Wheat Protein Water soluable protein, moisturize and sooth irritation; anti-aging
Wool Fat Moisturise & increase smoothness
   
X
Xylitol Moisturise & increase smoothness
   
Z
Zinc Oxide Reflect UV radiation, used in sunscreen

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