Background
The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs (also called bacteria or microbes) and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection. Within our bodies we have germs. In 1865 it was first proven that germs were the cause of disease. Germs are tiny organisms that cannot be seen by the naked eye. Each germ typically causes only one disease; for instance, a germ that causes scarlet fever cannot cause malaria. There are two types of germ found either on our skin or in our bodies. 'Good' germs which our bodies need to stay healthy and 'bad' germs that make us ill. Modern trends have us not only killing the 'bad' germs but also killing off any trace of the 'good' germs. So what is so bad about the 'bad' germs? The bad news is that sometimes germs cause diseases that sicken or even kill us. Everyday bacteria, protozoa, viruses and fungi are all germs that are needed to enable a child's immune system to mature. The major point of the Hygiene Hypothesis is that the cleanliness of our modern environments does not train the immune system properly, and it ends up malfunctioning.
Depending on the grade level or the prior knowledge of your particular class a brief explanation might be needed for the difference between bacteria, protozoa, viruses and fungi. The primary grade child (K-2) might be happy just knowing that some germs are good and some germs are bad, however, the intermediate children might ask what they all are. Bacteria are single-celled creatures that live just about everywhere on earth. They are so small that you cannot see them without using a microscope; they come in all sizes and shapes and can be good and bad for the human health. Viruses are not made of cells but need a host to survive. While bacteria can grow and reproduce on their own if they have enough food, viruses need to be inside the cell of a living thing. The virus must find a host and then its goal is to reproduce and spread. Most fungi are like plants because they are made up of many cells. Unlike plants fungi cannot makes their own food directly from sunlight, instead, fungi live rely on animals, plants and humans for their nutrients. Fungi love damp warm places like the cracks between your toes. Most fungi are harmless. Protozoa are not as small as bacteria. They are mostly single-celled, and have a nucleus. Some protozoa are parasites, in other words they live off of other things. Some protozoa actually eat bacteria and can be good because they also eat the waste of other organisms. Knowing how and why these germs harm us and how to protect ourselves from the 'bad' germs is the objective of this unit.
The Hygiene Hypothesis is a study that was developed to understand why certain children were at a higher risk to develop asthma. Throughout human life we have lived with dirt and microbes since the moment we were born. Our immune system evolved pathways to protect us. If these pathways are removed (as they are being removed today with all this cleanliness) part of our immune system will backfire. The hypothesis states that exposure to allergens in the environment early in life reduces the risk of developing allergies by boosting immune system activity. Conversely, relatively clean environment in early life would sway the immune system towards allergy-promoting responses. The hypothesis may explain the decrease of allergies in younger children of large families with 3 or more older siblings (due perhaps to repeated exposure to infection from older siblings); and the lower incidence of asthma and wheezing in children who go to daycare centers (where they are exposed to more infections).
Millions of people suffer from the sneezing and wheezing of allergies and asthma, and every year I see more and more of my students with inhalers. Our first thought is that perhaps the pollution is the cause but the Hygiene Hypothesis suggests otherwise. The story behind the hypothesis is in the late 1990s, Dr. Ericka Von Mutius, a health researcher, compared the rates of allergies and asthma in East and West Germany. Her hypothesis, as we all might assume, was that children growing up in the poorer, dirtier, and generally less healthful cities of East Germany would suffer more from allergies and asthma than youngsters in West Germany, with its cleaner and more modern environment. When, in 1999, von Mutius compared the disease rates she found it was exactly the opposite of her hypothesis. Children in the polluted areas of East Germany had lower allergic reactions and fewer cases of asthma than children in the West. What was going on? Von Mutius realized, there are many lifestyle differences between the former two Germanys, including family size and the more prevalent use of daycare for young children in East Germany. According to the Hygiene Hypothesis, the human immune system evolved two types of biological defenses. When one defensive system lacks practice fighting bacteria and viruses, perhaps from an overly sanitary lifestyle, the other system becomes too powerful and overreacts, as an allergic reaction, to harmless substances like pollen.
The Old Friends Hypothesis develops the Hygiene Hypothesis even further, it states that T regulator cells, cells that act to suppress activation of the immune system, only become mature and completely effective if they are stimulated by repeated exposure to microorganisms and parasites. This exposure occurs when coming in contact with a carrier. Living in an almost germ-free environment can make this T regulator cells less effective. T regulators are the generals of the immune system, they determine to a large degree the response of the immune system to various pathogens and antigens.
The Old Friends Hypothesis proposes that appropriate immune response is learned by repeated training of the T regulators through repeated exposure to microorganisms and parasites. The development of vaccines, hygienic practices, waste disposal, sewers, antibiotics and effective medical care have diminished or eliminated the prevalence and impact of many dangerous organisms, as well as relatively benign ones. This has been of obvious benefit and hundreds of millions of lives have been saved. However, our exposure to benign and apparently beneficial parasites and organisms has also been reduced as well. The central thrust of the theory is, therefore, that correct development of T regulator cells in individuals may depend on exposure to organisms such as helminths, which are parasitic worms. For this reason, helminths are used for worm therapy. Worm therapy emerged from the Hygiene Hypothesis. The idea is that because we are exposed to reduced immune-system stimuli, particularly growing up when our immune systems are developing, our immune systems do not develop properly. This parasitic infestation makes the T regulator cells more effective, therefore the helminths take a protective role in immunological disease development. Lack of exposure to sufficient benign organisms, particularly during childhood, is now accepted as the cause for the increase in immunological diseases and diseases for which chronic inflammation is a major component in the relatively sterile industrialized world.
The theory is that in today's society decreased family size has led to more cases of allergies and asthma. Families are getting smaller, children are not sharing bedrooms with other siblings, and they are staying inside most of the day. This results in the decreased contact between children and older siblings. Children are no longer exposed to natural microbes and infections at an early age so their immune systems are not prepared to fight off the infections later. In the past younger children were in contact with their unhygienic older siblings. It used to be that if one child had chicken pox, neighbors' children were brought in to be exposed to it. When one child had a contagious disease they could be sure of plenty of company. Now we keep our children away from the contagious diseases. The reverse of what our parents did. If a family has 5 or 6 children and the older siblings bring home viruses and infections the younger children are building their immunity. Imagine if the eldest of 5 children brought home a virus that gave exposure to his five younger siblings, strengthening their immune system. When the younger children began school and were exposed to the same virus they would have already built a resistance to it. With families getting smaller and cleaner the immune system suffers. That is why in the classroom today if one child get sick and shares the germs through personal contact or airborne germs there are some children that are more susceptible to being infected. If you look at the children that get sick after the first infection it is usually ones that are the oldest child in their family or the child who has no brothers or sisters. Using the sanitizer may stop the spread of the germ but then what happens to the younger siblings of the classmates? They do not get the immunity needed to protect them in later life.
The same theory can be associated with children that attend daycare or preschool at an early age. Many people think that a daycare is a breeding ground for viruses and disease which, in most instances, is true. Daycares today take pride in the clean, sterile, sanitized enriched environment. But this may be doing some harm to the immune system of a young child. Even though children who attend day care may appear to get sick more often than those who don't, this early exposure to illness seems to provide immunity and proper immune function for the future. While daycare children do tend to contract more infections early on, they also seem to build up their immunity by the time they start school, while children who were not in daycare tend to get sick often during the first few years of school. For the ever shrinking family it might be the place to build the resistance needed for later life.
Teaching in a school that is 99.6% African American I was intrigued to read the following information about African American children. As I read it I realized how true it was because many of the children in my building use inhalers with improper technique, many of which also have poor or incorrect personal hygiene.
The hygiene hypothesis, however, cannot explain the higher rates of allergic asthma among poor African Americans in the inner city areas. Even with equal access to health care, black and Hispanic children are more likely than white children to have asthma and their outcomes are often worse, a U.S. study has found. 2 The study found a number of racial and ethnic differences. Compared to whites, black and Hispanic children were more likely to be diagnosed with asthma at all ages, and black children of all ages and Hispanic children aged 5 to 10 were more likely to have potentially avoidable asthma-related hospitalizations or emergency department visits. "Our findings with regard to treatment patterns were mixed," wrote Kate A. Stewart, of Mathematica Policy Research in Chicago, and colleagues. "Black children, who at all ages were more likely to have a diagnosis of asthma and to have poorer outcomes than white children, were also more likely to receive recommended asthma medications, and especially inhaled corticosteroids." The researchers also found that black children were less likely to be treated by an asthma specialist, who would be more likely to follow treatment guidelines, including proper use of asthma control medications. 3
Viewed through the lens of the hygiene hypothesis the modern obsession or preoccupation with sterility, equating it with cleanliness and goodness, is revealed for what it is. It may not be beneficial to have a germ free environment.
Many people have a bottle of hand sanitizer in their car, on their desk, or in their home. We use it to clean our hands and kill the germs that could make us sick. But, what many don't know is that they might not want their hands to be too clean. Hand hygiene is one of the primary methods used to reduce the transmission of infectious agents. However, conflicting hand hygiene recommendations for different settings are causing confusion among the general public as to what is the best practice to follow or what products should be used for daily hand-washing and hand hygiene. Many people have the misconception that their immediate environment must be germ free. Well, this is only possible in a true germ-free chamber in a lab or in certain hospital settings. We live in a natural world that is full of microorganisms, living things that cannot be seen by our bare eyes. While some of the microorganisms can cause illness or diseases, others can be essential to our environment and wellbeing. Without good bacteria, we would be without our favorite yogurt, sauerkraut, or certain medicines! And without good bacteria or fungi, our earth would be full of biological debris. Furthermore, we should not forget that our normal, healthy body has various external barriers and internal mechanisms (immune system) to fight germs, as long as their numbers are not overwhelming. We also have bacteria living in and on our bodies that help protect us from the bad bacteria. So, understanding and learning how to control or deal with both the good and the bad microorganisms on our body and in our environment can help us make good use of those microbes, and at the same time, limit the spread of communicable diseases. The goal is to reduce the number of bad microbes to a level low enough for the body to reasonably fight off with its existing immune system.
The body parts of healthy humans and animals are host to a variety of microbes known as resident microbes. But through contact with other objects, the body also picks up other microbes known as transient microbes. A typical person's hand can carry 10,000 to 10 million bacteria, some resident and some transient. When humans or animals are sick or infected with specific microbes the number of microbes may increase. Many microbes are also present in the intestinal tracts of humans and animals; these are known as fecal microorganisms. A person's hands, arms, or fingers may become contaminated with fecal microorganisms after using the toilet. These must be removed by the mechanical friction of washing with soap and water or destroyed by the use of antiseptic solutions. The microorganisms from human and animal sources can be transmitted to hands, other people, foods, and anything else that the hand comes in contact with and vice versa. This is why good hand washing is important for reducing harmful microorganisms on our hands and for reducing the risk of transferring harmful microorganisms to others. An important key factor in the effectiveness of soap is the length of time it is left on the skin and the concentration of the product.
The burning question is can hand sanitizer replace hand washing? The majority of alcohol-based sanitizers in the United States contain ethanol or isopropanol or a combination of these two products. Most brands also contain a moisturizer to minimize irritation to the skin. Alcohol works immediately and effectively to kill bacteria and most viruses. Alcohol solutions containing 60-95% alcohol are the most effective. Alcohol gels work by stripping away the outer layer of oil on the skin, thereby destroying any "transient" microorganisms present on the surface of the hands. After use, re-growth of bacteria on the skin tends to occur slowly, thereby effectively keeping "residual" microbes that reside in deeper layers of skin from coming to the surface. To be most effective, a dime-size dollop of alcohol gel should be rubbed into the hands for 30 seconds. If hands are dry after only 10-15 seconds, it is likely that not enough sanitizer was used. Hand sanitizers should primarily be used only as an optional follow-up to traditional hand washing with soap and water, except in situations where soap and water are not available. In those instances, use of an alcohol gel is certainly better than nothing at all. Experts suggest that you can't rely solely on alcohol-based hand sanitizers. Alcohol can kill bacteria but not necessarily clean your hands. That is, it does not remove dirt, which includes organic material such as blood or feces. Soap and water must be the first choice in restrooms. 4
We all know the benefits of having the hand sanitizer sitting on our desk but I was surprised to learn that there are some negative effects of using too much sanitizer on the hands. First, exposing hands frequently to alcoholic hand sanitizer can have toxic effects on your body, in case they are ingested. Children are more vulnerable, as they love the strong smell and bright colors used in hand sanitizers, and I think about how many of my students still put their thumb or fingers into their mouth at an alarming rate. Now when I am supervising my children during the use of hand sanitizers I will make sure I tell them about the poisonous effects it has when their hands are put into their mouth. They will also be instructed as to how to use it correctly. The researched recommendation is that they should always use only a drop of sanitizer, rub it on their palms, back of hands, between the fingers, fingertips, and under the nails. I will try to buy hand sanitizers that have a foaming formula, due to the fact it dries faster.
Improper usage of the sanitizers can lead to more skin problems. The children should know to avoid hand sanitizer overuse if they have unhealed wounds or cuts on their hands. It might cause further skin irritation leading to itching, burning sensation, and skin rash. Hand sanitizers are flammable because of their alcoholic content, so always store them in a cool, dry place and keep them away from heat. A hand sanitizer also has a potential for abuse as an inhaler and regular sniffing of it gives a high. Considering these dangers of hand sanitizer overuse, it is wise to use them moderately.
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