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Skin care

Definition Function Basic skin care formulations

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Definition:

Largest organ of the body

It covers 1.2 2 meter square and wt about 4 kg

Completely exposed to the outside elements.

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Skin function: Barrier function. Temperature regulations. Protection against harmful

effect of UV light through our pigment cells

Sensory organ. production ... vitamin D. Immune function.

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Identification of skin type:

Normal skin : has an equal balance between water and oil, medium sized pores, well hydrated, smooth and firm to touch.

Dry skin : dull, rough to touch, flaky, small pores, lack of hydration.

TEWL: Transepidermal water loss, which kept to a minimum in by NMF, inters cellular lipids, keratinized cells. Alteration in TEWL can cause dry skin and it is affected by factors like central heating, wind , cold, contact with water, nutrition, surfactants.

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3. Oily skin : results from hyper production of sebum, skin looks as orange peel; large hair follicle, slight shine prone to black head, and acne.- Sebum production are controlled and affected by the following factors cause: - Genetic, hormonal, stress, diet .. Etc.- Factors may cause temporarily sebaceous gland activity :

Menstrual cycle, contraceptive, pregnancy.

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- Sebum composed of : triglcerides, free fatty acids, wax esters, cholesterol.- Max secretion at puberty at about 20 years then decreased by 28% after each decade. 4. Combination skin :

Mixture of dry and oily skin.

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Basic skin care:

Skin care forms the largest sector of cosmetics market

Condition of face , neck and hands indicate the general condition of skin

Skin is the body sacrificial organ, the first to show sign of stress

Skin reflect general mental and physical well being.

People spend a lot of money on skin care products.

Skin care should not be for treatment only, it should be priority and daily routine.

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Consumers needs can be roughly divided into Two areas (table 1):

Protection fromRepair of

UVRIRR

WindCentral heating

ChemicalsCold

PollutionInsects

Dry skinSunburns

AcneWrinkles

Puffy eyesCellulite

Skin cancerPigmentation

Age spotsScares

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basic skin care is daily routine of skin care :

This include five steps :1. Precleanse : warm water on cotton ball to soften and loosen oil and dirt.2. Cleans.3. Toners and astringents : to prepare skin to absorb ingredient from moisturizer.4. Moisturizer.5. Sun screen.

Remembers ABCs of sun safety .. :Avoid peak sunlight hours 10 a.m. to 3

p.m.Wear protective clothing (e.g. hat).Use sunscreen with SPF of at least 15.

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Cleansing products

Soaps/synthetic detergent-based productsSoaps (effective, inexpensive,alkaline)

Synthetic detergents includes:Shower gelLiquid hand soap Foam bathFacial cleanser

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Facial cleaners normally contain : Formula 1. Mixture of SAA (anionic , anionic/ amphoteric).2. Thickening agents : NaCl,and other viscosity modifiers: cellulose derivative, PEG esters, poly acrylic acid (carbapol®).3. Refatting agent : usually natural oil.4. Humactants : glycerol, propylenglycol.

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5. Silicon derivatives : increase in popularity because it impart smoothness without stickiness (e.g. quaternary poly dimethyl silicon, dimethicone copolyol).6. Hydrolysed protein.7. Natural oil and extracts.8. Proteolytic enzymes : keratolytic agents.

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Cleansing productsCleansers for oily skinFacial mask and exfoliating lotion rather than facial scrubs.

Formula:Synthetic detergent system

AstringentOil controlling agents and soothing agents (oily controlling cleansers)

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Cleansing productsEmulsion cleansersCleansing creamRinse-off emulsion(foaming cleanser)

Cleansing fluid emulsion (milk/lotion) sebum absorbing material

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- Some skin care ingredients 1. Plant extracts commonly used in skin-care products Their beneficial effects might be due to its moisturizing, antioxidant, anti-inflammatory and photo-protective properties of natural ingredients.

2. Special additive / nutrients: - Vitamins: Vitamin C has been used extensively in cosmetic formulations for their skin lightening activity, free radical scavenger and collagen synthesis anti-aging properties. Ascorbic acid was found to cause epithelium thickening, with cells of larger volume in the granular and spiny layers. Vitamin E protect skin from ultraviolet light, reducing the appearance of fine lines and wrinkles, helps delay ageing and has skin moisturizing properties due to its antioxidant activity.

Special additive / nutrients:

- Proteins.

- Essential fatty acids: Evening primrose, flaxseed or borage oils were found to be beneficial for atopic skin conditions due to their gama lenoleic acid content.

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Alpha- hydroxy acids- AHAs are a group of organic carboxylic compounds. AHAs most

commonly used in cosmetic applications are typically derived from food products including glycolic acid (from sugar cane), lactic acid (from sour milk), malic acid (from apples), citric acid (from citrus fruits) and tartaric acid (from grape wine).

-.Glycolic acid, having the smallest molecular size, is the AHA with greatest bioavailability and penetrates the skin most easily; this largely accounts for the popularity of this product in cosmetic applications.

Alpha- hydroxy acids

- Epidermal effect AHAs have a profound effect on keratinization; which is

clinically detectable by the formation of a new stratum corneum. It appears that AHAs modulate this formation through diminished cellular cohesion between corneocytes at the lowest levels of the stratum corneum.

- Dermal effects AHAs with greater bioavailability appear to have deeper

dermal effects. Glycolic acid, lactic acid and citric acid, on topical application to photodamaged skin, have been shown to produce increased amounts of mucopolysaccharides and collagen and increased skin thickness without detectable inflammation, as monitored by skin biopsies.

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The active component is astringent.

Material with astringent properties can be classified as a. Short chain alcohol e.g. ethanol.b. Organic acid with low molecular wt e.g. lactic acid.c. Metal salt of organic or inorganic acid e.g. Al sulfate.

d. Vegetable extracts containing tannins e.g. Witch hazel.

TONERS

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TYPES OF TONERS

Astringent lotions ( very oily & acne prone skin )high Ethanol % ( Astringent , Antiseptic , Smooth sensation )

Antimicrobial ( Benzalkonium Cl )

Keratolytic ( salicylic acid ) Toners & Fresheners

low% of Ethanol , Menthol

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Skin Barrier Function Moisturizing Agents Humectants, emulsifiers and commercially available

moisturizers have been found to influence the barrier function in normal skin. In damaged skin, topically applied substances can both accelerate and retard normalization of the barrier function to water. Furthermore, skin susceptibility to irritants is influenced by certain moisturizers, which clearly indicates that ingredients are not as inert to the skin as previously considered. This opens up new possibilities to treat more efficiently various skin abnormalities and different body areas, and to understand various requirements among consumers.

Before going through moisturizers and their types and applications, we will briefly discuss the structure of the skin and types of human skin.

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Structure of the skin:

A vertical section of the skin reveals three distinct layers, namely the outermost epidermis, the dermis and finally the hypodermis or subcutaneous layer (Fig.1).

a) Epidermis: The epidermis is a cellular structure, made up of many

layers of cells. The special structure of the epidermis is classified as stratified squamous epithelium and is typical of vertebrate animals.

It is responsible for producing the main barrier known as the horny layer or stratum corneum, which forms the outermost part of the epidermis. The horny layer is made up of water-resistant dead cells, called corneocytes, which are cemented together with a complex lipid material.

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Fig.1: Structure of the skin

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Fig.1: Structure of the skin

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Epidermis

The epidermis varies in thickness from 75 to 150 micrometers (µm) in most areas to 6 mm on the palms of the hands and the soles of the feet.

In terms of cells the epidermis consists of about 35 cell layers of which 15-20 layers make up the horny layer.

The lower living layers of the epidermis can also be subdivided as follows:

the germinative or basal layer; the stratum spinosum or prickle cell layer; the stratum granulosum or granular layer, which is

characterized by the presence of distinctive keratohyalin granules.

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Epidermis

The function of the epidermis is to produce and maintain an efficient barrier called the stratum corneum (horny layer).

Skin is continuously losing moisture to the atmosphere by diffusion of water vapour through the stratum corneum and the sweat glands. The keratinized cells, NMF and intercellular lipid keep this transepidermal water loss (TEWL) to an acceptable minimum.

Epidermis renews itself once every 2 months.

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Moisturizing factor (NMF) The NMF acts as a water reservoir in the horny

layer which keeps the latter pliable and feeling soft.

The composition of the NMF is : Components %

Free amino acids 40Lactate 122-Pyrrolidone carboxylic acid 14Urea 4Mineral Salts 16Sugar, organic acids, peptides 11Urocanic acids 3

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The dermis

The dermis functions as a supporting frame to the epidermis, supplying it with nutrients via the blood capillaries. It also supports the sensory nervous system, secretary glands and hair follicles.

Unlike the epidermis, which is a cellular structure, the underlying dermis consists of connective tissue. Other examples of connective tissue in the body include bone, cartilage and loose areolar tissue.

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The dermis - collagen

The dermis consists of connective tissue, which consists of a fairly dense network of protein fibers (such as collagen and elastin, collagen forms the major constituent of the fibrous protein which gives the skin its tensile strength) embedded in a hydrophilic viscoelastic gel called the ground substance.

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The dermis – ground substance Ground substance.The dermal ground

substance consists of salt, water and glycosaminoglycans. The latter form complexes with protein molecules known as proteoglycans. The best-known examples of 'glycosaminoglycans' are hyaluronic acid and chondroitin sulfate. Hyaluronic acid is known to play a vital role in the hydration of tissues since it carries with it a large volume of water.

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The hypodermis

Below the epidermis is a layer of fatty or adipose tissue called the hypodermis. The cells in this layer synthesize and store fat as an energy reserve. This is to help insulate the body from low external temperatures and to act as a buffer against trauma. On a more familiar note, the hypodermis provides the body with its contours, whether they are attractive curves or unwelcome bulges.

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Skin permeability

In normal intact skin it has been established that the keratinized corneocytes and the largely non-polar lipid intercellular cement of the horny layer are the major factors involved in the maintenance of an efficient barrier.

The function is lost if the stratum corneum is removed by tape-stripping techniques but is re-established again after a few days when the stratum corneum grows back.

In addition, dietary deficiency of essential fatty acids such as linoleic acid results in skin with poor barrier properties. The vast number of products and chemicals that come into contact with the human skin make it of vital importance that the horny layer is well looked after.

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Skin permeability Many raw materials which are commonly found in cosmetic

and toiletry products permeate into and through the stratum corneum; some can also act as penetration enhancers for other specific materials. Examples of penetrants include water, glycerol, ethanol, phenol, urea, aluminum salts and essential oils.

Common penetration enhancers include water, organic solvents such as propylene glycol, surfactants and dimethyl sulfoxide (DMSO). Occlusive dressings are often used to increase the hydration of the stratum corneum. This is used to promote the penetration of topically applied steroids. Permeation tends to occur through the intercellular matrix, but hair follicles, sebaceous glands and the sweat ducts have been shown to provide a faster alternative route for transport of highly polar molecules.

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Skin permeability

Damage to the skin may be caused by: mechanical stress, chemicals, light and micro-organisms (bacteria, yeasts, moulds and viruses).

To the cosmetics manufacturer, chemicals and light-induced damage are the most important considerations.

Appropriate safety tests ensure that the potential for a product or its component raw materials to cause adverse reactions is reduced to a minimum.

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Skin permeability

Adverse reactions include skin irritation and sensitization which results in varying degrees of inflammation of the skin. Inflammation of the skin is known as dermatitis, of which there are many types.

Inflammation involves all the changes which take place in an injured living tissue, provided that the injury does not immediately kill the cells or destroy the tissue structure. The visual signs of this activity, known as the triple response, are:

- erythema ; redness - oedema ; swelling - flare ; more extensive reddening and swelling. Each stage of the triple response can be measured

objectively, but these changes are accompanied by subjective manifestations (burning, itching, and stinging) which must also be taken into consideration.

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Types of skin:

Skin is often classified into four types according to the activity of the oil producing sebaceous glands. This classification is commonly used for facial skin because the skin type can vary in the individual depending on age, body site, season and state of health.

1. Dry skin.

2. Oily skin.

3. Normal skin is not particularly oily or dry. It is smooth and firm to touch and the skin pores are barely noticeable.

4. Combination: this type of skin has a tendency to be greasy in the central T-zone of the forehead, nose, central cheeks and chin. The skin on the other areas is normal or dry.

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Dry skin It has been established that water keeps the

horny layer supple and ensures neutralization of acids and alkalis. A water content of 10-20% in the stratum corneum is said to be required to keep it soft and pliable.

An alteration of the barrier (by repeated exposure to surfactants for instance) can cause an increase in TEWL to the extent that water is lost faster than it can be replaced from the underlying tissues. This results in the horny layer drying out, precipitating dry skin conditions.

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Dry skin

Dry skin feels taut, rough and itchy. Closer observation reveals the presence of very fine wrinkles and, at a more advanced stage, large scales.

The surface of severe dry skin is cracked and is reddened (erythema) as a result of the dilated peripheral blood capillaries in the dermis. Environmental factors, sunlight and ageing, plus numerous skin diseases and dietary deficiencies, all produce dry skin.

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Oily skin

Oily skin results from, the excessive activity of sebaceous glands which produce the lipid secretions known as sebum.

There are several factors which can cause and/or contribute to oily or greasy skin; genetic inheritance, hormonal changes, diet, stress and external agents (chemicals, ultraviolet light). Changes in hormone levels which occur during puberty, the menstrual cycle, use of oral contra ceptives and pregnancy tend to influence the activity of the sebaceous glands which can result in a flare-up of oily skin.

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Basic components of moisturizing products

A good moisturizing formulation is non-irritant, easy to spread over the skin, easy to rub in without ‘soaping up’, able to leave the skin feeling soft rather than sticky, and pleasantly perfumed. If the product is to be unperfumed there should be no fatty base odor. The basic components of a moisturizing product include moisturizer, emulsifier system, water, preservative and antioxidants if necessary.

Moisturizing preparations can be classified into five groups.1. Day preparations.2. Night preparations.3. Hand and body lotions.4. All-purpose products.5. Barrier creams.

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Day preparations

Day moisturizing products tend to be light, oil-in-water emulsions which are designed to spread easily and rub into the skin quickly.

They have evolved from the traditional vanishing cream system which is an oil-in-water emulsion that is based on high-quality stearic acid as the oil phase. Commercial triple-pressed stearic acid consists of a mixture of stearic and palmitic acid with a tiny amount of oleic acid.

Partial neutralization of the fatty acid (16-20%) with a base such as triethanolamine or potassium hydroxide produces a soap which constitutes the emulsifier system.

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Day preparations

These soap-based oil / water creams give a wet feel on the skin when first applied. They do not rub in well and appear soapy and white.

Secondary emulsifiers such as self-emulsifying glyceryl monostearate and other nonionic surfactants such as polyethylene glycol esters and fatty alcohol ethers can be used to prevent any skin dryness which may result from use of the alkali-stearate soaps.

Other emulsion stabilizers include the carbomers and fatty alcohols such as cetyl alcohol. Cationic surfactants, such as stearalkonium chloride, are used to a lesser extent as emulsifiers. Because of their substantivity to the skin, they may be used to give an additional smooth skin feel after application.

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Night preparations

Products which are supposed to be left on the skin overnight serve to provide vital nutrients to the skin which may have been lost during the day. These products, like massage creams, tend to be water-in-oil emulsions which are available as creams and viscous lotions. Water-in-oil emulsions tend to be less cosmetically elegant than the oil-in-water types because of the difficulty of rubbing them in; in addition they are apt to leave a feeling of stickiness on the skin.

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Night preparations

One of the advantages, that water-in-oil systems have over their oil-in-water counter parts, is that the continuous oil phase has direct contact with the skin and forms a protective film immediately without any detergent action.

In this way the dispersed water particles are trapped in the oil, by the water-in-oil emulsifiers and the product is more resistant to being washed off. Therefore such products have remained popular with people with dry skin.

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Night preparations

Traditional night creams were originally based on the beeswax, borax and mineral oil systems.

Today other waxes, vegetable oils and silicone oils (instead of mineral oil) can be used as emollients and co-emulsifiers such as quaternary ammonium salts or the volatile silicones such as cyclomethicone.

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Night preparations

A new range of silicone emulsifiers such as lauryl methicone copolyol and cetyl dimethicone copolyol have recently become available. These can be used to produce stable water-in-oil formulations with up to 74% water with little or no waxes. Therefore the resulting formulations exhibit excellent moisturizing properties combined with improved aesthetics.

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Hand and body lotions

Products for use on the hands and body tend to be similar in formulation to the day moisturizers. They are usually lotions and sometimes aerosol mousses rather than creams, for ease of application. This can be achieved by increasing the viscosity of the water phase with agents such as the carbomers and cellulose derivatives.

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All-purpose products

As their name suggests, all-purpose creams and lotions can be used as a moisturizer or a cleansing cream on the face, hands and body.

A simple, all-purpose cream can be formulated with polypropylene glycol (PPG) stearyl ether as the emollient and stabilized with stearyl alcohol and nonionic emulsifiers.

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Protective products

(a)Simple hand lotions Hand preparations are available as creams, lotions and

gels. The skin on the hands, like that of the face, is continuously exposed to the environment as well as constant immersion in hot detergent solutions. If adequate protective measures are not taken then the hands can become extremely scaly, dry and inflamed, resulting in an increased TEWL and impaired barrier properties. Hand-care products are applied to re-hydrate, smooth and leave a residual non-tacky protective film on the skin.

In addition to emollients, they can incorporate a healing or soothing agent, such as allantoin, urea and lanolin which confers some barrier properties to the product.

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Protective products

(b) Barrier creams Barrier creams, like hand creams, are

protective products. In addition, however, to acting as moisturizers, they prevent external materials from permeating the skin, such as water, defatting solvents, soil and dirt.

The formulation of barrier creams will be determined by the type of external materials from which the end-user requires protection.

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Protective products

Protection from water Formulations which exhibit water repellency

may be based on petroleum jelly , lanolin and silicones.

An aerosol mousse, as an alternative, offers a product which is hygienic and easy to apply. Kaolin may be included as a skin protectant. Glyceryl monostearate (self-emulsifying grade) allows the product to be easily washed off after use.

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Protective products

(c) Protection from soil and oils Non-oil soluble film formers such as gum acacia and

tragacanth or sodium alginate can be used to provide oil repellency. Glycerin helps to plasticize the gum film.

(d) Deep engrained dirt on hands A vanishing cream-type formula can be used to

prevent the hands becoming ingrained with dust and dirt. The effect is achieved by rubbing the soap into the pores, which ultimately helps in the removal of soil when the hands are washed.