How does soap kill germs?

Answer 1

This really depends on what you mean by germs. The most common intent behind the word is bacteria and viruses (virii). Also of concern are spores and fungi (fungal agents). You can search resources like Wikipedia, WebMD.com, or MayoClinic.com for information on these various agents, and on the effectiveness of various soaps, lotions, and wipes. In general most soaps utilize chemicals that break down fats and oils, bind to dirt and other particles, allowing them all to be rinsed away in a flow of water. Surface bacteria and virii tend to be washed away with the dirt and oils, which does not necessarily mean they are killed. "Antibacterial" soaps include one or more of a few common antibacterial agents that either prevent bacterial reproduction or kill bacteria outright. In combination with the more traditional cleaning ingredients in soap they can help eliminate a few (and only a few) more bacteria. They can also remain on the skin to help kill additional/newly-introduced bacteria for a period of time after handwashing. There are several serious concerns about the use of antibacterial agents in soap: 1) People may be less careful about handwashing, missing the critical time-based and mechanical elements of handwashing in the assumption that the antibacterial agent will make up the difference. 2) Though not proven in the case of antibacterial handsoaps by direct evident (yet), the antibacterial agents themselves have been shown to promote the survival of antibacterial-resistant strains of otherwise common bacteria, possibly leading to bacteria that are no longer affected by the antibacterial agents. Worse, they will also be immune to many prescription antibiotic medications, requiring the use of more expensive and sometimes more dangerous antibiotics. 3) Some of the antibacterial agents persist in the environment. They can kill benign organisms that are beneficial to the environment but not dangerous to humans or other animals. Some of the agents can concentrate in tissues of fish and sea mammals, possibly achieving toxic levels, leading to sterility or even death. This same concern applies to many medications that are passed through urine and feces into the environment. 4) Antibacterial agents do not kill viral agents, like the common cold or flu. Coupled with item 1 above this can leave one exposed to remaining viruses that will cling to foods during a meal, then entering the body to do their worst. Soaps are made using a variety of materials, some for cleaning and some for helping to retain moisture on the skin (moisurizers) and some for enhancing the "clean" smell of hands (essentially no scent at all) with a pleasant fragrance. It is usually the cleaning ingredients that promote the removal and death of pathogens along with dirt and oils. Some of the chemicals do interrupt pathogens, either inhibiting reproduction or killing them outright. The effect (stop spread or kill germ) depends on the chemical agent and they pathogen. Some chemicals will kill bacteria but not "viruses"/virii. Other chemicals will kill both. ("Killing" a virus is really a misnomer since a virus is not, by classic biological definitions, a living entity.) In the end what matters most is how you wash your hands. Many sources, from the World Health Organization to several famous research hospitals and universities, provide simple guidelines for handwashing: 1) Use soap and warm water. 2) Wet the hands first, removing any loose dirt. 3) Throughly lather with the soap. 4) Keeping hands outside the water, work the lather around the entire hand, between the finders, around and under the fingernails, and up to the top of the hand (near the wrist). Do this for at least 20 seconds. 5) Throughly rinse hands in water, actively working the hands together to remove the soap. The water and the mechanical action of rubbing the hands will promote greater removal of dirt and oils with the soap. 6) Dry the hands with a clean towel or disposable towel. Again, the mechanical action of drying removes even more remaining dirt, oil, and soap. More than you may have wanted to know, but it is vitally important that you know how, when, and why you should wash your hands. Your health and the health of others depend on it.