Science Fair Project Encyclopedia
Hygiene is the maintenance of healthful practices. In modern terminology, this is usually regarded as a particular reference to cleanliness.
Outward signs of good hygiene include the absence of visible dirt (including dust and stains on clothing) or of bad smells. Since the development of the germ theory of disease, hygiene has come to mean any practice leading to the absence of harmful levels of germs.
Good hygiene is an aid to health, beauty, comfort and social intercourse. Good hygiene directly aids in disease prevention and/or disease isolation. (That is, if you are healthy, good hygiene will help you avoid illness. If you are sick, good hygiene can reduce your contagiousness to others.)
Washing is the most common example of hygienic behavior. Washing is often done with soap or detergent which helps to remove oils and to break up dirt particles so they may be washed away.
Hygienic practices -- such as frequent hand washing or the use of boiled (and thus sterilized) water in medical operations -- have a profound impact on reducing the spread of disease. This is because they kill or remove disease-causing microbes (germs) in the immediate surroundings. For instance, washing one's hands after using the toilet and before handling food reduces the chance of spreading E. coli bacteria and hepatitis A, both of which are spread from fecal contamination of food.
Origin of the term
The word hygiene is derived from the name of the Greek goddess of health known as Hygieia. She was the daughter of Asclepius and sister to Panacea. While her father and sister were connected with the treatment of existing disease Hygeia was regarded as being concerned with the preservation of good health and the prevention of disease.
Commercial and cultural aspects
TV advertising campaigns in many countries have attempted to influence public opinion that only clean and sterile is healthy and safe. While the general advantages of hygienic behavior are undisputed, there are questions about the long-term benefits and dangers of an extreme position.
In particular, the use of antibacterial soap in the home is of doubtful benefit and may actually be harmful. Antibacterial soaps contain a low concentration of a chemical to kill bacteria. These chemicals may be similar to ones used in fighting infection. Their use in everyday cleansers contribute to the evolution of resistance in common bacteria to these chemicals. This would make antibiotics far less useful in combating infections. There are also growing concerns that the overuse of antibacterial soaps create an environment in which a growing child's immune system is understimulated, leaving them more susceptible to disease when they are older. There is evidence that the presence of 'dirt' in children's lives could enhance the development of their immune systems  and there are suggestions that use of some cleaning products can harm the unborn . The question then arises as to how one defines dirt: by the absence now of naturally occurring pathogens and other dangerous substances; or by the build-up and unforseen effects of the chemicals and pharmaceuticals that we use to treat our personal, domestic and wider environments.
The term hygiene has also been used in wider contexts, to include preventative as opposed to motivational initiatives in affecting human behaviour. See the article on Frederick Herzberg in this context.
During the Indian Ocean Tsunami of December 2004 the rapid burial of the dead in mass graves in the mistaken belief that it was hygienic to do so was criticised by some scientists. They described it as unscientific and a misdirection of resources which would be better directed towards the survivors. 
Some hygienic practices
- Daily washing of the body and hair
- More frequent washing of hands and/or face
- Cleaning of the clothes and living area
- General avoidance of bodily fluids
- Holding a hand in front of the mouth when sneezing or coughing
- Suppression of habits such as spitting or nose-picking
- Use of condoms in sexual relations
- Washing hands before eating
- Not licking fingers before picking up sheets of paper
Food preparation and consumption
- Cleaning of food preparation areas and equipment
- Washing of hands after touching uncooked food when preparing meals
- Non-sharing of cutlery when eating
- Refrigeration of foods (and avoidance of certain foods in environments where refrigeration is or was not feasible)
- The labeling of food to indicate when it was produced (or, as food manufacturers prefer, to indicate its best before date)
- Storage of human food so as to prevent contamination by vermin
- Disposal of uneaten food and packaging
- Institutional dish sanitizing
- Use of sterile bandaging and dressing of wounds
- Sterilisation of instruments used in surgical procedures
- Sterilisation of instruments used by hairdressers
- Sterilisation by autoclave of instruments used in body piercing
- Burial or cremation of the dead
- Use of sewerage systems to remove human, industrial and agricultural liquid and suspended solid waste
- Garbage removal
- Protection of health of workers
- dry cleaning
- Hygiene hypothesis
- vacuum cleaner
- washing machine
- five second rule
- Occupational hygiene
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