Medicines and cosmetics hold a significant position amongst the man-made materials. Disinfectants are chemicals that kill or stop the growth of bacteria. They are of two types.
1. Germicides.
These are strong chemicals and cannot be used on the skin or other body tissues, for example, phenol. Sodium hypochlorite (NaOCl) and bleaching powder [Ca(OCl)2] are germicides. Bleaching powder is used in swimming pools as a disinfectant. These compounds are poisonous and should be handled with care.
2. Antiseptics.
Disinfectants that can stop the growth of bacterial and can also be used on the body are called antiseptics. In many cases antiseptics are dilute solutions of germicides. Some common antiseptics are tincture of iodine used for minor cuts and 3% solution of hydrogen peroxide.
Most of the medicines today are prepared in large chemical laboratories. Drugs used to relieve pain are called analgesics. Drugs which prevent the growth of bacterial are called antibiotics.
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Cosmetics are materials applied to make the body more attractive. Facial creams, Nail polishes, lipsticks and many kinds of lotions are common cosmetics made up of chemicals obtained mainly from petroleum.