Soap and Syndet

 CLEANSING

The removal of dirt, sweat, oil, bacteria, etc., from the skin by using a cleanser and water is called the cleansing of the skin. 

WHAT IS A SOAP

Soap is a salt of fatty acid. Soap is mainly used as a surfactant for washing, bathing, and cleaning. They are manufactured by a process called saponification.

 "Soaps for cleansing are obtained by treating vegetable oils and animal oils and fats with a strongly alakaline solution. The alkaline solution, often called lye, brings about a chemical reaction known as saponification".

Water and oil don't mix, so water is not enough if we try to clean an oily stain from a cloth or the skin. We need soap. 

Many substances are applied to human skin for hygenic, cosmetic, and other purposes. Soaps are probably used more frequently and on human beings than any other single preparation.

Wide use of soaps and ease of application to more or less large skin areas during washing, bathing, and showering has frequently lead to the idea that they could serve not only for their basic purpose of cleansing but also as vehicles for "active" therapeutic ingredients.

In more recent years, probably the most frequently added "active" ingredient in soaps is anti-infectives which have been shown to have a strong effect against several infectious and "normal skin" micro-organisms.

Hydrophilic and Hydrophobic

Molecules form soap with a "head" that likes water (hydrophilic) and a long chain that hates it(hydrophobic).

Working of soap: 

When soap is added to the water, the hydrophilic heads of its molecules stay in the water (they like it), while the long hydrophobic chains join the oil particles and remain inwards(escaping from water). In that way, they form circular groups named micelles, with the oily material absorbed inside and trapped. 

The surfactant used by soap is very aggressive and harsh to the skin. They contain chain lengths from C10 to C14. This harsh surfactant is responsible for common cutaneous problems like Erythema, Xerosia, and Pruritus. 

the pH of soap:

The pH of the soaps ranges from 9.5 to 11, which is highly alkaline, and if this alkalinity can lead to further damage.

Effect of soap on the skin: 

During cleaning, Stratum Corneum is exposed to a relatively high concentration of surfactants (5%-20%). At these concentrations, Surfactants:

Damage stratum corneum proteins

Damage stratum corneum lipids

Increase Leaching / Removal of NMFs

The extent of damage depends upon the nature of surfactant and Cleansing conditions (Water temperature & hardness etc.)

1). EFFECT ON PROTEINS:-

Water absorbed by the Stratum Corneum during cleansing results in protein swelling. The harsh surfactant o soaps and the alkaline pH increase the swelling further. Due to this, the corneocyte envelope gets damaged, and thus NMF's gets lost as TEWL(transepidermal water loss).

2). EFFECT ON LIPIDS:

The high pH of soaps induces a charge in the lipid bilayer. Due to this, the bilayer structure gets altered, eventually leading to the breakup of the barrier. Thus there is a loss of lipids. 

Formation of Skin Barrier: 

The formation of the barrier depends upon three enzymes, which are called lipid processing enzymes. They are: 

A) Acid lipase 

B) Beta glucocerebroaidase

C) Spningomyelinase

The enzyme which breaks the corneo desmosomes or which takes part in the desquamation process is Serine Protease.

When the skin pH increases:

When the pH of skin is increased, these two activities result in a Disturbed Skin Barrier.

1). There is reduced activity of Lipid Processing Enzyme; improper lipid metabolism and organization result in loss of mortar.

2). Increased activity of serine protease; this leads to premature loss of corneocytes/bricks.

Due to change in pH:

1). Dry skin 

2). TEWL increases

3). Susceptibility to infections with bacteria, viruses, and fungi.

4). Entry of allergens and irritants

5). Various cutaneous disorders, as lack of defense of the skin.

Almost all the cleansing products are based on surfactants. These molecules have a special construction that makes them compatible with both oils and water. Since oil and water do not usually mix, you need surfactants to remove oils from skin and hair. Soaps and syndets are all surfactants. Detergent is just a synonym for surfactant.

 Repeated use of Soaps:

Due to the repeated use of soaps, the pH of the skin becomes alkaline. In an alkaline environment, the skin barrier is more prone to damage. 

SYNDET: 

Syndet are called Synthetic detergents. Syndets are produced from fatty alcohols, which are derived from natural oils. Syndets are made by esterification, ethoxylation, or sulphonation of oils, fats. 

Commonly included surfactants in syndets are Alkyl Glyceryl Ether sulfonate, Alpha Olefin Sulfonates, Betaines, Sulfosuccinates, Sodium cocoyl Monoglyceride Sulfate, Sodium Cocoyl Isethionate.

Syndets have an acidic ph which is like that of the skin.

The surfactant used by syndets is alkyl isethionate, which is very mild and gentle on the skin. 

WHERE ALL SYNDETS CAN BE USEFUL:

Skin pharmacology and physiology 2006 confirms that syndet is useful in preventing and treating skin diseases like irritant contact dermatitis, atopic dermatitis, ichthyosis, acne vulgaris, and Candida albicans infections. 

The benefit of syndet:

Syndet reduces the severity of atopic lesions, dryness, erythema, and improved hydration and skin texture in 28 days.

DIFFERENCE BETWEEN SOAPS AND SYNDETS:

There are many differences between soap and syndet. some of given in the table.

SOAP	SYNDET
Soaps are highly alkaline	Syndets are 100% soap free alkali free with a mild acidic pH
Soap destroys the acid mantle/skin barrier	Syndets protects the acid mantle/skin barrier
Soap dries the skin	Syndet prevent TEWL and does not dry the skin
Soap does not protect the skin	Syndet protects skin against pathogens
Soap clogs pores	Syndet clears pores
Soap irritates sensitive skin	Syndet suitable for all types of skin
Soap causes TEWL	Syndet prevents TEWL
Soap damages the skin	Syndet protects the skin

TEWL = Trans Epidermal Water Loss