**6. Algal alginate in the cosmetic industry**

A cosmetic product can be defined as any natural or prepared material that in contact with teeth and mucous membranes of the mouth cavity and external parts of human body (epidermis, hair, nails, lips, and external genitals). These products can be in different forms as cream, lotion and spray. Nowadays, many people use cosmetic products and their ingredients, some for therapeutic purposes and others to enhance their beauty [92]. However, it should be noted that the purpose of using a cosmetic product cannot be to cure any parts of the human body. This kind of products are generally used after different dermatological issues like acne, eczema, and so on [93]. Recently, a new word called "cosmeceutical" has been used to indicate specific cosmetic products, which include active ingredients. These products are not considered drugs or cosmetics, but they show medical or drug-like benefits. The cosmetic/cosmeceutical consumers desire the products that are safe, effective, protective, elastic, and natural with good quality [91, 92].

Recently, cosmetic consumers have begun to pay attention not only to the effects of the product as a whole, but also to the content of the products [94]. With the increase in acquiring knowledge about the ingredients, awareness about the unhealthful side effects of synthetic cosmetic ingredients (irritation, allergic reactions, etc.) is created among the consumers more than before [91, 93, 94]. Additionally, Cosmetics Europe – the community for the cosmetics and personal care industry – has forbidden the use of synthetic solid plastic particles, which cannot be biodegradable by marine organisms for saving aquatic ecosystem in any types of cosmetic products [95]. This situation has contributed to conduct more research on finding new, natural, eco-friendly and biodegradable polymer sources to produce natural ingredients [91, 95]. At this point, algal alginate has drawn attention, thanks to its biological activities as an anticoagulant, antiviral, anticancer, antimicrobial, moisture retention, anti-irritating, antioxidant, anti-inflammatory, and antibacterial matter [17, 78, 90, 91]. As a result of having these aforementioned properties, alginate can be used as an abrasive agent, antioxidant, and thickening and stabilizing agents in the cosmetic industry [17, 90]. From this point of view, algal alginate is a promising candidate as a cosmetic ingredient.

The skin is the biggest organ of the human body and covers all the other organs [74, 91, 96]. It has three layers: epidermis, dermis, and hypodermis. The epidermis is composed of five stratums: basal, spinous, granular, lucid, and corneum. This layer contains melanocytes, langerhans, keratinocytes, granules, and dead keratinocytes [91, 93]. Melanocytes include melanin that determines the skin color and both of the melanocyte, and keratinocyte cells heal the skin damages. The stratum corneum acts like a water diffusion barrier. Thus, it protects the skin from dehydration and irritation and allows the human to live in air [91]. The health situation of the cells on the epidermis layer changes according to the weather conditions and nourishment schedules. Dead cells remain on the skin nearly for two weeks. After that, they through desquamation and recuperation stages and these stages take one month. Peeling products have the ability to remove dead cells and improve skin health without causing any negative effects on the skin. In this way, these products can help to make these processes faster [93]. Researchers have found that the optimum diameter of microparticles which is used in the peeling product formulation is 750 μm. Alginate microparticles are a good candidate as abrasive agents, thanks to their regular and spherical shape. The addition of starch to these microparticles increases the surface unevenness and inequality. This starch-alginate microparticles combination shows the effect on the skin as synthetic balls do. They have a unique potential for replacement with synthetic ones, as they are natural, biodegradable and environmentally friendly compounds [95].

*Algal Alginate in Biotechnology: Biosynthesis and Applications DOI: http://dx.doi.org/10.5772/intechopen.101407*

Naturally the skin has the ability to synthesize antioxidant agents to protect itself from reactive oxygen species (ROS). Also, it has been known that the skin increases ROS production when exposed to UV radiation. Under these circumstances, oxidative stress causes the existence of wrinkles, dehydration, inflammation, melanoma, and skin cancer. For preventing skin aging and other aforementioned cutaneous disorders, the skin has to be supplied by antioxidants via cosmetic products [91, 93]. At this point, algal alginate is a promising candidate as a cosmetic ingredient with significant antioxidant activity [80, 91]. This activity related to its molecular weight, sulfate content and anionic groups [97]. Thus, it can be used as anti-aging, antiwrinkle, and smoothing agents [93, 98]. Additionally, it has the ability to absorb several 100 times more water than its own weight to support the cell and regulate the water distribution in the skin, and thus protect cells from caving in [15, 91, 98]. Considering these properties, it has been inserted in a wide range of products such as hand lotions, ointments, fat-free creams, facial masks, and dental materials to improve nutrients diffusion and absorption [78, 80, 99].

Alginate can be used as thickening agent in shampoos, lotions, or other cosmetic products, which include huge amount of water for instability inhibition purpose [98]. Also, this polymer has ability to stabilize the viscosity to offer good liquidity in cosmetics [79]. This is the major reason of using it in cosmetic formulations [91]. Also, it helps to maintain the organoleptic features (taste, sight, smell, and touch) of cosmetics, thanks to its favorable activities [80, 91].
