From doctors and public health experts to our mothers, it seems that everyone is telling us to wash our hands. Hand washing is one of the best deterrents to the spread of illness. To remove dirt and germs from our bodies, soap relies on the same basic chemistry that keeps oil and water from mixing.
To understand the process, we are going to have to go back to high school chemistry. Soap and detergent molecules have two ends. And just like the opposite ends of a magnet, both sides are attracted to different substances.
Although we refer to anything we use for washing as soap, most of the products we use today would be classified as detergents. The difference is found in the materials used to make them. Soaps are made by the chemical reaction of animal fats or plant oil with an alkaline substance like lye. Petroleum-based products, rather than plant oil or animal fats, are used in the manufacture of detergents. The mechanism with which they remove dirt from our bodies, however, is the same.
The first end of the soap molecule is the hydrophilic end. This is the combination of two Greek roots: hydro, meaning "water," and philic, meaning "loving." In other words, water loving. Just like its name, it loves water, so that end clings to water easily.
The other end of the soap molecule is the hydrophobic, or "water-fearing" end. The Greek word phobic probably does not need much explanation. This end of the soap molecule is repelled by water, but it is attracted to the grease, dirt and oil on our skin.
When dirt, soap and water are mixed together with agitation, such as when you rub your hands together, one end of the soap molecule is attracted to the dirt, and the other end is attracted to the water. As the soap is rinsed away, it takes the dirt and grime down the drain with it.
In the middle of the 1990s, manufacturers began touting the advantages of antibacterial soaps over regular soap. Most of these products contain triclosan, a biocide (or bacterial-killing) agent. A study published in the September 2007 journal "Clinical Infectious Diseases" states that antibacterial soaps are no better than regular soaps at removing germs from the skin. Since bacteria are known for developing resistance to agents that kill them, researchers also fear that widespread use of these products could lead to further antibiotic resistance.
When hand washing is not possible, people often turn to hand sanitizers. While hand sanitizer use in schools reduces absenteeism, studies show that hand washing with plain soap and warm water removes more bacteria from the hands than hand sanitizers. Hand sanitizers are better than nothing, but a good hand washing with soap and warm water is the best way to remove germs from your hands, and in turn prevent illness.
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