People have been using cosmetics since the time period of the ancient civilizations. Women in ancient Egypt have used kohl as eye shadow. Cleopatra allegedly bathed in milk for a whiter and softer skin. Later during the medieval period, Greek women even used toxic lead carbonate to whiten their complexion just to be in the fad. Cosmetics have become an essential part of most people's lives that manufacturers have made a source of living from it. It may be possible that all people, regardless of age, sex and culture must have used any form of cosmetics.
Cosmetics technically refer to substances or products intended to be applied on the external parts of the body including teeth and mouth. Cosmetics are used either to cleanse, to lace a nice smell, to protect and to alter the appearance. As for the chemistry of cosmetics, usual ingredients or materials used in making cosmetics are water, fragrance, emulsifier, color, preservative, pH stabilizers and thickener.
Emulsion is a concept on which most cosmetics are based. It could either be some oil droplets in water or several water droplets in oil. Water and oil never mix with each other, which is why emulsifiers are used in the process of cosmetics making. The emulsifiers prevent water from separating with oil and vice versa, thus a homogenous and evenly textured product is produced.
Preservatives are added to cosmetics so that microorganisms are prevented to grow. Bacterial or fungal growth may spoil the products and cause harm to the user. Commonly used cosmetics preservatives are tetrasodium EDTA, benzyl alcohol and parabens. Polymers are examples of thickeners added to cosmetics to achieve desired consistency. They are either natural (polysaccharides) or synthetic (polyethylene glycol). Polyssacharides are usually obtained from seaweeds in the form of carrageenans which came from red and brown algae.
The pH stabilizers affect the acidity of the cosmetics, color creates an appealing effect and fragrances make the cosmetics smell good. Moisturizers are cosmetic products used for treating dry and scaly skin. They prevent additional loss of water or moisture from the skin (occlusion) and add substances to the skin which make it able to retain moisture (humectants). Occlusive moisturizers contain alcohol and some mineral oil. Humectant moisturizers have glycerine, and fruit acids.
Surfactants added to soaps and shampoos account for the cleaning ability of the cosmetic products. Usual surfactant molecules used in cosmetics manufacturing are lipophilic (fat soluble) and hydrophilic (water soluble). Lipsticks are made with the concept of water solubility. It is made of water insoluble coloring, wax and non-volatile oil. Fake tans are cosmetic products which alter its color once it contacts the skin. Its active ingredient is a colorless dihydroxyacetone which changes colors as a chemical reaction with the amino acids on the top layer of the skin. The color produced is permanent; however the tan is also shed from the skin along with the constantly shedding skin cells.
The use of cosmetics must be done carefully because it may contain ingredients which may be harmful to the skin. Some people are allergic to makeup and other cosmetic products. The chemicals added to the cosmetics like fragrance and preservatives may cause allergic dermatitis. To determine is the skin is prone to allergies; a patch test should first be performed.