**5. Conclusions**

*Surfactants and Detergents*

sequence is as follows:

*4.2.2 Surfactants in hair care*

although low pH is a potent defense against microorganisms, it helps the synthesis of key enzymes that act as a skin barrier [13–16]. High pH in the absence of surfactants was seen to cause SC swelling and lipid rigidity resulting in skin irritation and feeling of discomfort that explains the feeling of tightness and dryness of the skin on using soap. Synthetic detergents (syndets), namely, sodium cocylisethionate (SCI) and sodium isethionate, on the other hand did not induce such feelings. Detailed studies

Other mild nonirritating cleansers frequently used are sodium salts of lauryl ether sulfates (SLES) containing 1–3 moles of ethylene oxide (EO). It is an excellent degreasing and foaming agent without the harshness of its parent sodium lauryl sulfate (SLS). Detailed studies have demonstrated that addition of EO groups in the main chain reduced detergency and skin irritation. Although SLES (1EO) is extensively used in body washes and shampoos, SLES (3EO) being milder is used in baby products as baby skin is thinner and prone to irritation. Cocoamidopropylbetaine (CAPB), sulfosuccinates, and alkylpolyglucosides (APG) are even milder than SLES. In fact in a scale of 1 to 100 where 1 is the mildest and 100 is the harshest, the

[13, 15] revealed that syndets had pH in the range 5–7 soaps had pH >10.

Water < APG < SLES+CAPB (2:1) < syndet < SCI < soap < SLS [13].

CAPB has therefore been used successfully in tearless shampoos, and often mixtures of SLES:CAPB (2:1) are used in baby shampoos. Very high-end mild products are formulated with CAPB and APG's mixtures containing glycerin as humectant.

The human hair consists of the outermost layer called the cuticle which consists of dead and overlapping hard scalelike structures. The inner layer is the cortex that imparts strength and color to hair, and the innermost layer is the medulla which is present in thick hair but often absent in thin and fine hair. Detailed studies [12] have revealed distinct differences between Caucasian, African, and Asian hair. Not only the cross sections are distinctly different, but the very structures and strengths are different. While the African hair is fine and tends to be kinky, Asian hair is straight, thick, and strong. Sebum secreted from the scalp acts as an emollient that coats the hair shaft making it soft, shiny, and manageable. Atmospheric dust and aerosols present in the environment is readily captured by hair owing to its large surface area making it appear greasy, and because colonies of bacteria flourish due to sebum, it gives rise to an unpleasant odor which may be highly embarrassing. Although the mechanisms of cleaning remain the same as discussed in an earlier section, for skin, extra caution is necessary while designing a cleanser for hair as harsh chemicals and unfavorable pH may make hair dry and brittle [9]. Very clean hair is unattractive and may appear to be dry, lifeless, without shine or gloss, difficult to comb, and unmanageable as it tends to tangle. It is the presence of moisture and oil, natural or otherwise, that imparts a smooth, silky appearance that makes hair manageable and looks beautiful. Therefore, ingredients in shampoos need to be carefully selected such that balance of oil and moisture is maintained for hair to appear attractive and lively. Because hair washing practices vary from country to country and the quality of hair is very different, shampoo formulations used in different countries are different although the same ingredients may be used. For oily hair, sodium lauryl sulfate (SLS) or triethanolamine dodecylbenzene sulfonate (TEA-DBS) is used solo being an excellent degreaser and foaming agent or often as a mixture with its milder counterpart SLES (1EO). A conditioner is usually not added in the formulations for oily hair. However, for normal and dry hair, a milder surfactant like ammonium lauryl sulfate (ALS) with a conditioner like fatty alcohols or fatty esters, vegetable and mineral oils, and humectants (glycerin) is

**8**

In this chapter, we have briefly reviewed various surfactants commonly used in household and personal care industry. The mechanisms at the heart of the cleaning processes whether it be for skin, fabrics, or hair has been discussed. Because local conditions like water hardness, temperature, food habits, nature of food stains, extent of atmospheric pollution, nature of soil, and most importantly cleaning habits differ from country to country, surfactants need to be chosen judiciously so as to optimize performance under those local conditions. Mild surfactants suitable for skin and hair care for people with sensitive skin and babies have been discussed in some detail.

## **Author details**

Ashim Kumar Dutta India Glycols Limited, Kashipur, Uttarakhand, India

\*Address all correspondence to: askdu1@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
