Skin Cleansing

Hair Structure and Its Care Hair structure The hair consists of an elongated part, which grows from the dermis and protrudes above the surface of the skin, known as the hair shaft Hair grows from a hair follicle —an elongated tubular structure in the skin, which is lined with cells. One or more sebaceous glands open into the hair follicle. A fatty substance called sebum is produced by the sebaceous glands and passes via a short duct from the gland into the hair follicle.

An arrector pili muscle is attached to the hair follicle; when this muscle contracts, it causes the hair to stand up The bottom of the follicle is wider and thicker. The region below the lower end of the follicle is called the papilla . It is also called the dermal or follicular papilla ; it contains blood vessels that nourish the hair follicle..

KerMhous shdt Arre-c•tor pii rnusde matrix papilla Structure of the hair.

At the bottom of the hair follicle are the unique cells that produce the hair itself. These cells have enormous replicating abilities . They divide, and as more and more cells appear, the older ones are “pushed” upward in vertical rows and gradually degenerate . Since the cells degenerate and die as they move up the follicle, the upper part of the hair is made up of dead cells , which remain attached to each other by an intercellular cement-like substance. In other words, the hair that protrudes above the skin is actually made of dead keratinous material..

The only living parts of the hair are the cells at the bottom of the hair at the base of the hair follicle , which constantly divide and determine the hair quality As long as the cells at the bottom of the hair follicle (which form the base of the hair) are healthy and normal, the hair can continue growing. If, for any reason, those cells are destroyed, there will no longer be any hair growing from that follicle..

Hair Color The melanocytes in the hair follicle give the hair its specific color. Different types of melanin, which differ from one person to another according to each one’s genetic characteristics, determine the hair’s final color. Transverse section of the hair shaft The hair shaft is made up of three layers: Medulla : a thin layer in the center of the hair shaft. Cortex : this is the largest layer of the hair shaft it is made up of hair cells that are constantly moving upward, and as they do so, they degenerate and die.

Cuticle: it is a sort of thin outer wrapping. This layer is made up of cells that partially overlap. The cuticle is relatively impermeable, and protects the hair from penetration of foreign materials..

Life cycle of the hair Every hair follicle has a regular life cycle of growth, rest, and falling out. The cycle of any single hair is not dependent on the others. It is normal and natural for up to 100 scalp hairs to be shed daily and approximately 100 other hairs will appear in their place..

Stages in the life cycle of the hair Anagen : The Active Growing Phase : the hair cells at the base of the hair follicle are dividing repeatedly, and the hair grows steadily Catagen : The Transition Phase: This relatively brief phase . It is a transitional phase during which the hair stops growing. Telogen : The Resting Phase: the mechanism responsible for the replication of the cells at the base of the hair, and the subsequent hair growth, are inactive for several months. By the end of telogen , the hair is only loosely attached to the follicle, and can be easily pulled out simply by brushing or washing the hair, etc..

Resumption of Active Growth : a new hair appears from the same follicle during the next anagen (growth) phase. As this new hair grows, it pushes the old one, which is shed from the follicle. Normally, at any given time, approximately 80% to 90% of the hairs on the head are in the anagen (growth) phase, and 10% to 15% are in the telogen (resting) phase..

Life cycle Of a hair (A) Active growth phase (anagen). (B) Transition phase (catagen'..

226 (C) Resting phase (telogen). HANDBOOK OF COSMETIC SKIN CARE (D) Resumption of the growth phase (new anagen phase)..

Hair growth rate Scalp hair grows at a rate of up to 0.4 mm a day. However, Body hair grows at a slower rate than scalp hair, at 0.2 mm/day Factors that may affect hair growth include: pulling or stretching the hair Local Pressure on the Scalp Externally Applied Substances Local Heat.

Hair Care Products 1) Shampoo: Washing hair : The scalp and hair are normally lubricated by sebum, which is secreted from the sebaceous glands. This oily secretion protects the hair and skin against water loss and gives the hair its sheen. On the other hand, there is some disadvantage to the oily layer on the scalp—dust, soot, and other environmental pollutants tend to stick to it..

In order to remove the dust, soot, and other grime, as well as the cells of the keratin layer that have peeled off, the oily layer on the scalp and hair must be removed, since these particles are embedded in it. The same principle that applies to the action of soaps and surfactants for cleansing the skin also applies to shampoos for cleaning the scalp and hair. By rinsing with water. The surfactants, the active ingredients in shampoos, surround and trap tiny droplets of fat (that contain the grime), and these are removed from the scalp and hair.

(A) (B) The principle of action of shampoo is identical to that of soap: (A) A particle of fat and grime adherent to a hair shaft (B) Surfactants trap the fat particle and remove it from the hair..

Shampoos are designed to replace ordinary soap. Why ? Normal soap has a high pH, which may damage skin and hair. The use of normal soap with tap water produces calcium salts that adhere to the hair. This causes the hair to look and feel dull, brittle, and disheveled, making it hard to comb. A shampoo should be adapted to the individual in terms of the following aspects: Hair type (oily, dry,perm,dyed ).

Specific scalp problems (Dandruff) Safety requirements ( irritation) Personal preferences of the user ( consistency and texture , particular fragrance, ease with which it spreads through hair, amount of foam it produces , easy to rinse off , degree to which it makes the hair soft, supple, and shiny and easy to comb and manage the hair after using the shampoo)..

Components of shampoo 1- A mixture of several surfactants 2-Moisturizers :( someone with dry hair requires a shampoo with a less vigorous, gentler cleaning effect, and an added moisturizer). 3- Conditioners ( to make the hair soft, shiny, and easier to comb and manage). A shampoo that contains conditioner has to fulfill several functions, the chief being cleansing the hair. Such a shampoo cannot achieve the efficiency of a pure conditioner used independently after washing and cleaning the hair..

4- Foaming Agents: ( there is no need for an extensive lather to clean effectively: the effectiveness of a shampoo is mainly determined by how the hair looks and how the user feels after washing the hair, and not by how much lather it produces). 5- Water Softeners (Chelating or Sequestering Agents): Water softeners bind (“ chelate ”) calcium and magnesium ions present in water, and thereby prevent their attachment to fatty acids, which would create salts that are not easily soluble. Without the addition of water softeners, the salts that form would affect the cleansing ability by coating the hair. Leading to loss of its luster..

6- Thickeners: These make the shampoo thicker. Thickeners have nothing to do with the cleansing properties of the shampoo. However, they make the shampoo look more attractive. Also, a thicker shampoo is less likely to dribble down and get into the user’s eyes 7- Dyes and Fragrances: it is preferable not to use shampoos that incorporate synthetic dyes or perfumes that are particularly strong. 8- Preservatives.

Special Ingredients in Shampoo various vitamins (e.g., vitamins B and E), plant extracts, egg, honey, jojoba, aloe vera , and others. The use of these ingredients may have significant effects on sales. Applying such substances to the external hair can affect its appearance (but not its growth!). The hair will look shinier and “silkier,” and will be easier to comb and manage.

Gentle shampoos Gentle shampoos are shampoos for people with delicate skin or, more particularly, for babies. They also are designed not to cause stinging of the eyes, which results from certain ingredients in shampoos getting into the eyes They are not supposed to contain ingredients that may cause irritation, particularly perfumes and certain preservatives. Many contain a relatively higher concentration of amphoteric surfactants ..

Hair Conditioners The cuticle is the outer layer of the hair shaft. Its integrity and health determine the appearance of scalp hair. The properties of hair, such as its softness, luster, and pliability, are determined mainly by what happens on its surface. Hair conditioners treat the external surface of the hair..

A normal, healthy cuticle looks like the arrangement of roof tiles. Should the cuticle be damaged, the surface of the hair shaft becomes irregular and disorganized, and the hair becomes rougher and coarser. The hair becomes more brittle, and the ends tend to fray and split..

Hair can be damaged by: washing the hair too frequently, too frequent combing and brushing, overuse of a hair dryer, perming, dyeing with permanent dyes, bleaching and exposure to certain environmental conditions, such as the sun’s radiation, wind, and swimming pool water. If the external surface of the hair is damaged, the hair shaft develops negative electrostatic charges along its length. As a result of the electrical charge, the hairs repel each other, which make it very difficult to comb or manage the hair..

The main functions of a hair conditioner are: To create a coating that covers the outer, rough layer of the hair—this coating gives the hair its smooth, uniform look. To neutralize the electric charges on the surface of the hair. By doing this, the hair does not look so unruly, and becomes much easier to comb and style.

The active ingredients in conditioners affect only the surface of the hair. They do not penetrate the interior of the hair, and certainly do not affect the hair follicle. Their effect is only temporary and is lost within a few days. Types of hair conditioners: cationic surfactants Since cationic surfactants carry a positive electric charge, they are attracted to these negative charges and become attached to the surface of the hair. Thus, the outer surface of the hair acquires a uniform coating..

Since cationic surfactants contain long fatty chains, they produce a fatty layer on the surface of the hair that gives it a soft, smooth feeling, and a shiny appearance . The more the outer surface of the hair is damaged, the more negative electric charges its surface carries and the stronger the bond with the conditioner . The cationic surfactant is therefore attached most strongly to those areas of hair that are the most severely damaged (as a result of dyeing, bleaching, or perming), so the end result is that the surface of the hair develops a smooth, uniform look..

Cationic polymers . The cationic polymers that are used in hair conditioners contain substances such as: silicones, polyamides, polyamines, and substances based on cellulose They become attached to the surface of the hair as long units of polymer chains. Cationic polymers fill in the defects in the hair shaft, thus allowing light to be reflected more completely from the hair, since the hair surface is now smooth..

These products are also cations (i.e., they carry a positive electric charge), so they also reduce the negative static electric charge on the surface of the hair. Protein conditioners The protein in these conditioners is extracted from animal tissues (such as keratin, collagen, casein, and others) or from other sources, such as certain plant proteins..

In preparing conditioners for the hair, the proteins are chemically broken down into smaller components. In that form (peptides or amino acids), they can attach themselves to the hair and fill in the cracks and gaps. This strengthens the hair shaft and repairs the split ends. When the hair is washed, these substances are washed out of the hair shaft..

Frequency of use of a hair conditioner: The frequency with which a hair conditioner is used varies in accordance with the user’s personal preference People with healthy hair do not necessarily need a conditioner . If the hair has been damaged as a result of bleaching, perming, or exposure to dry weather, then a conditioner is helpful Conditioners should not be used too much, since if an excessive amount settles on the hair, the hair tends to lose its shine..