Asthma rates have been rising over the
past couple of decades in the developed world. There is a leading
theory that explains this phenomenon: the hygiene hypothesis. It
suggests that living conditions in developed countries are a little
too clean, and children aren´t being exposed to microbes that
stimulate the maturation of their immune systems. Hence, this lack of
this immune system training leads to less knowledge about what's
harmful and what's not. When in contact with harmless particles –
such as dust or pollen – the body overreacts and treats them as
deadly threats.
This theory is supported by studies
that show that farmers who are in contact with crops on a daily basis
develop fewer allergic diseases. To add to this, farm animals
increase exposure to germs and endotoxins, which stimulate immune
response.
Although the hygiene hypothesis does a
good job explaining the protective effect of the exposure to microbes
in the prevention of allergies, it fails to explain what's happening
with asthma. Several studies show that respiratory infections in
early childhood may actually be a risk factor for asthma, instead of
preventing it. Contrary to what was expected, asthma rates
skyrocketed in areas that were not particularly “clean”.
In order to prevent and treat it
properly, it is crucial to fully understand the causes and cellular
mechanisms of asthma. It is known that there is an inflamation of the
airway that leads to a bronchoconstriction that difficults breathing.
The subjacent causes of it, though, are still unclear, as there is,
in some cases of asthma, an allergic component, but not in all of
them.
Currently, there is the belief that
the factors proposed by the hygiene hypothesis protect people from
developing allergic asthma, but also are causing them to develop
nonallergic asthma. Thus, the overall increase of asthma rates is at
the expense of the nonallergic type.
In developed countries, it is certain
that several diseases are being prevented by the enhancement of
hygiene, and throughout the years there are less and less cases of
severe respiratory infections, as well as infections in general.
However, modernization can increase inflamation, as kids and overall
population have a sedentary lifestyle that promotes it. Obesity
boosts inflamation all over the body, the lack of exercise affects
lung strength, which prompts respiratoty infections, and smoking and
air polutants irritate the airway.
There are others viewpoints on this
topic: some researchers say microbiota is the one to blame. When
compared to healthy subjects, asmathics possessed higher bacterial
amounts and diversity in the lower airways. This microbiome
composition in asmathics was highly correlated with the degree of
bronchial hyperresponsiveness, which could indicate that these
bacteria potentiate allergic responses. In addition, it was shown
that they could also impact host response to viral infections that
are asthmagenic.
What do you think about this topic?
What comes to your mind?
Do you think we live in a over-hygienic
world?
Do we need more exposure to the outside
world?
What do you think about the widespread
assumption that children should be exposed to as many allergens as
possible in order to prevent asthma?
Here are the articles I used:
Rising Prevalence of Asthma
Respiratory Infections and Asthma
Microbiota in Allergy an Asthma
The Hygiene Hypothesis
Tiago Reis
Hi everyone!
ResponderEliminarI believe that the outlook of this issue has not been really clarified. The fact of not having the real causes despite doing research abundantly makes arise many logical hypotheses without having anything trustworthy. In practice, this means that we do not know what to advise and there is some uncertainty about what is right or wrong. Cleanliness both in excess and defect is harmful, as happens with the microbiota.
In my opinion, I do not think we should expose ourselves to a large number of allergens on purpose or that we should isolate ourselves in a bubble from everything else. As in many fields, everything, taken to the extreme, is bad.
Raquel.
Este comentario ha sido eliminado por el autor.
ResponderEliminarHello everyone!
ResponderEliminarThank you for talking about this item Tiago, because the hygiene hypothesis has always drawn my attention since I heard about it the first time. I suppose that the reason is that I´ve always been surrounded by animals and my family and I never have had serious diseases, neither allergy nor asthma as you comment. So I think I made a kind of popular belief which connected both facts. Thus, for me there are some advantages in a little bit of dirt, like if it made you stronger anyhow.
I don´t know if we live in an over-hygienic world, but what I know is that we live in an more hygienic world than in the past. It seems obvious because we now know about many diseases and its way of transmission and we use to try to protect ourselves of them. In addition, most of the time, cleaning is more comfortable than dirt, so we profit progress in this term.
So yes, in my opinion we must expose ourselves to the outside world. It doesn´t mean we must get crazy and take every risk, but I´ve always believed that what doesn´t kill you makes you stronger and in this context too. I mean, we shouldn´t be so afraid about getting diseases and of course we shouldn´t become obsessed with cleaning.
Having said that, I think my position is very clear. I do think that exposing children to allergens will probably make his immune system stronger, although there are many other factors which affect it and determine the health or the diseases that they´ll suffer.
Hello!
ResponderEliminarIn first place, I want to say that I actually believe in the hygiene hypothesis as there are many studies which show us how the excess of clearance affect us nowadays.
I think that in order to talk about an over-hygienic world we should divide it (unfortunatelly) in both sides: developed countries and developing countries. If we talk about developing countries the answer is easy: no, they are not over-hygienic. Basically because thay can't, they don't even have enough water to drink so they can't use it in showering. Then if we move to deveoped countries I think that it depends as well, but generally it tends to be more over hygienic, maybe due to the busy lifestyle we follow.
I belive that we spent a lot of time sheltered in different closed places: our room, gym, library, classes, office... and we shoud spend more time in contact with nature or maybe just breathing fresh air and be more in contact with the outside world.
Hello classmates!
ResponderEliminarI’m not 100% agree with some of those theories. Obviously they explain part of some asthma cases but even nowadays we don’t know exactly what it causes asthma. About the hygiene hypothesis: maybe part of this disease is due to an allergic reaction that can be explained by this lack of contact with a huge diversity of antigens when we are developing our immune system. But there are much more ambient factors that can also develop asthma.
On one hand, pollution plays an important role too. Air pollution (vehicles’ toxic gases, tobacco components, industry expelled gases...) increase the sensibility of our airways producing a permanent inflammation of our bronchus. Hence, when in determinate situations we need an increase of oxygen volume, like when we are doing exercise or when we have an anxiety reaction and we start to hyperventilate, our bronchus are not functional and they are not able to expand and proportionate the adequate oxygen supply. Then, this works like a vicious cycle because when we feel that we are not able to breathe we have more anxiety and our system tries to increase our breathe rate.
Finally, I also want to make some emphasis in one point. There are no studies that can corroborate that, but I believe that part of the asthma phenomenon is related with having or not having practised exercise during our childhood (when our lungs and airways were growing up) and obviously during the rest of our life. I mean, if we do sport we increase our lung capacity and we are less susceptible of suffering asthma.
30-4-17
Noemí
Hello everyone!
ResponderEliminarThank you for choosing this subject as it is crucial that we know about asthma and its possible causes - in the future, we most likely will have patients who suffer from it.
I find it quite amusing that even without knowing it is called “the hygiene hypothesis” our culture and in my case my family believe that this hypothesis is not a hypothesis at all– it is common knowledge. As a person who was brought up in the countryside myself, surrounded by nature, allergens, soil, and dust I was quite surprised when suddenly I developed allergies later on. It was not until I came here to study that I started with the allergies, so in my own experience, I guess the onset of both allergy and asthma may be related to the environment and your surroundings as well as your natural predisposition to develop it.
I am also aware of the fact that some infections in early childhood can provoke asthma. For instance, in case you have bronchiolitis, which is caused by the respiratory syncytial virus, during the first two years of life, you are at risk of having asthma in the future. Children who were bedridden with bronchiolitis are at significantly heightened risk for both recurrent wheezing and childhood asthma. I have read an article a few months back, from which I learned that the relationship between bronchiolitis and asthma is yet to be established. It was also mentioned that the inner properties of the infectious virus played an important role in the recurrence of infections in children or perhaps in the asthma development itself. (You can read the article here, if you, like me, are interested in learning more about this connection:www.atsjournals.org/doi/full/10.1164/rccm.200603-435PP).
We are on the same wavelength on the hygiene part of the question: we are indeed an over-hygienic and under exercised society. Evidently, we have come a long way on the hygiene side of the equation, but we are very distant from where we need to be when it comes to promoting heathier lifestyles and making healthier choices. “When diseased, the lung is like a cracked bell, muffled in tone and without resonance” – this is a great analogy to explain that it is imperative that we start taking better care of our lungs, by making permanent changes to our lifestyle and by preventing respiratory infections.
Having said all of that, I do believe that we need to expose children to allergens. Living in a bubble, over protected from the outside world may in fact perpetuate this kind of illnesses. I am also of the opinion that more research needs to be carried out on this subject; if asthma rates are rising and we are not sure what causes it nor which pathogens are related with the development of this disease, then we need to keep searching until we find a more accurate hypothesis. It may be that this “hygiene hypothesis” is in fact proven right, but I do believe that more factors need to be taken into account, such as other infections that may attack the lungs as well as incapacitating diseases or paralysis that may contribute to lung disease or lung failure.
Hello!
ResponderEliminarIssues like this are often listened at present. What is better, to endanger your children's health or forbid them to play with mud? Maybe the solution is to let them being dirty with responsability. However, I think the "fashion idea" of expose children to dust and microbes is too much. Hence, I suppose the best is to take them to the mountain, field and beach, teach them to treat with animals, and maybe this way children develop a good health.
Hi everyone again!
ResponderEliminarFirst of all, say that I really agree with few of the comments that you have done, particularly with Raquel. The best would be find the exact point in which the sanitization keep us save of the mortal infections, and at the same time protect us of the allergic reactions, like asthma.
Futhermore, and I don’t know if there are studies thereon, maybe we have to consider that children are increasingly expose to chemical products(paints, plastics). These products, new or modified every year, also could be related with this increase of the asthma rates(as non-natural substances that they are) and the body could “disoriented”.
Regarding the third question, I think that we need going back over our steps and get out of the house, go to park, to country, practice camping, hiking… outdoor activities which zoom in us with our original habitat. Especially these kind of exercises would be useful in kids who live in the cities and have little contact with nature.
Finally, this point could be address from many perspective, and all of them easily reprehensible, because we have not a real solid basis.
Carlos Veiga