Overly Sanitized Environments Lead to Poor Health?

bignickel writes "A recently-released study examined the health implications of living in an overly hygienic environment. According to the 'hygiene hypothesis,' living in such an environment early in life can lead to problems with allergies and autoimmune diseases. The study compared lab rodents with rats and mice living in the wild. Time to stop Lysol-bombing the house?"

No shit Sherlock

[ds_job]

All I had to do was google for "Eat a peck of dirt" and the sixth on the list is a New Scientist [newscientist.com] page from 1998

I was very interested in your article on the possible dangers of excessive hygiene ("Let them eat dirt", 18 July, p 26). As a child I remember being told by my mother that "you have to eat a peck of dirt before you die", a peck being two gallons. Is this another case of scientists catching up with what has been common knowledge for generations?

If you want to fork out for the premium content you can get the full text here. [newscientist.com]
I'm presuming that in eight years time some other publication will 'discover' this again and maybe someone will link to me instead of Susan Taylor...

Re:Farm Workers Without Allergies

[wwest4]

I'm also not a doctor, but I've heard that the human body can also become aware of an allergen after repeated exposure... poison ivy or cat dander, for example. People who were not allergic to these things can apparently develop an allergy to something that didn't elicit a reaction before.

Found the article from '93

[Anonymous Coward]

at Discover Magazine:
http://www.discover.com/issues/sep-93/features/ofp arasitesandpo264/ [discover.com]

Re:Farm Workers Without Allergies

[Ryanwoodings]

The May (2006) issue of National Geographic has an article titled "The Misery of Allergies", which lends a lot of credibility to your story. The article says scientists aren't sure what causes allergies, but there is evidence that shows that growing up in "dirtier" environments leads to fewer allergies.

http://www7.nationalgeographic.com/ngm/0605/featur e4/index.html [nationalgeographic.com]

Re:Polio / Middle-class diseases

[Surt]

A lot of people like to think things are related. That's why we have scientists and statistics. In this particular case, scientists sampling water supplies of the middle/upper classes actually discovered for a fact that polio was less prevalent in the cleaner water supplies of the middle/upper class, and that reduced exposure in early infanthood or through the mother's immune system led to more crippling cases (the greater severity of polio infection after infanthood was also well researched and understood).

Here are a couple of resources:
http://www.amphilsoc.org/library/mole/n/nycpolio.x ml [amphilsoc.org]
http://www.pbs.org/wgbh/rxforsurvival/series/disea ses/polio.html [pbs.org]

So now you don't just have to like to think they were related, you can just say the link was scientifically proven.

Outdoors, animals and allergies

[Hoi Polloi]

I've found that my animal allergies vary from animal to animal (within the same species). My previous cat would sometimes start me sneezing hard. Getting her saliva on me would trigger an especially bad reaction. My current cat however hasn't given me the slightest problem. I know my allergies are still there because they flare up around different cats or at animal shelters.

I have some doubts about the dirt hypothosis beyond just animal allergies. I also grew up playing in the woods and being outdoors a lot. I also camp and hike a lot and drink straight out of (clean) streams. I still get bad reactions to many pollens. Maybe you have to have parasites or repeated infections as a child for this possible effect to show up.

Re:Farm Workers Without Allergies

[timcharper]

Something interesting about allergies is that the tendency to develop allergies is inherited, but which allergies they develop don't appear to be inherited.

I just did a research paper on the subject recently (within the last yeaar). If you can find it, here's a reference to an article about it:
"Allergy Myths: Cleaning the Air." Saturday Evening Post 271.4 (1999): 26-28. EBSCOHost. Online. 13 Oct. 2005.

Re:Too much of a good thing

[Anonymous Coward]

The problem with Lysol bombing the house is that it not only kills the disease ridden bacteria but the "Good" stuff as well. Then IMHO, itsa the continual destruction of this type of bacteria that has more effect on your individual suitability to a particular allergy.

I have travelled the world and visited many places that you would find hard to locate on a map. In general I don't get Delhi Belly, Khartom Kramps or the Tokyo Trots as I try to "Fill up" on the local bacteria ASAP.
On one trip arond 1993 to the Uzbek/Iranian border(Dry Hot Dessert) my american colleague insited in only drinking pre bottled drinks and eating tinned/canned foods or steaks burnt to a frazzle. I ate the local fare (apart from pickled camel). Guess who spent most of the trip on the John. It certainly wan't me. His face went white when I tucked into some of the dishes offered by our hosts in their Yurt. Ok, the place wasn't lysol clean but it was Ok.

One last point.
Many people claim that have an allergy to a particular food. Often this is not an allergy but an intolerance. This is far (in most cases) from an allergy. If a Bee sting can kill you without an ingection of Adrenaline then you have an Alergy. If you get a rash from eating a particular type of seafood then that is an intolerance.
Just my 0.02sum worth.

Re:Outdoors, animals and allergies

[rk2z]

That would be because most people who are allergic to cats are actually allergic to cat saliva and because cats clean themselves by licking, their dander causes allergies by proxy.

Re:The future

[Lord Ender]

Your friend probably has colitis. This is a disease that is quite common in the Western world, but does not exist at all in the "developing" world. The theory is that if your immune system is never exposed to parasites, it forgets what it is supposed to be attacking and goes after your large intestine. This will cause constant internal bleeding, mucus, and diarrhea. If it gets bad enough, you will die of malnutrition and dehydration. It usually starts happening, right out of nowhere, when you are in your 20s.

Because nobody likes to talk about digestion, there have been very few studies of colitis or attempts to find cures. People love to raise awareness and money to fight cancer and other disease, but ignore this one because intestine problems are not polite to discuss. It's a damn shame.

Be careful...

[LunaticTippy]

I don't react to poison whatever either. My brother was the same way for years and years, but eventually developed a sensitivity to it. His doctor said that erratic large exposure to allergens can eventually produce sensitivity.
So don't seek it out and show off like I did.

Re:Farm Workers Without Allergies

[binarybum]

With all allergies there must be one or more exposures before the body develops the characteristic over-response, attacking harmless substances as though they really were a threat. You cannot be allergic to anything until you are exposed at least once.

Incorrect. Cross-reactivity can make you allergic to things you've never been exposed to. Here is a lay article, [about.com]

Re:Predisposition

[hr raattgift]

So, here's an interesting theory

"Hypothesis", not "theory".

Pregnant women who are around allergens sometimes pass those allergens through to the developing embryo, which spontaneously aborts if it can't handle it

It's unlikely.

The developing embryo takes a few days from fertilization to implantation. This sometimes leads to light bleeding or minor cramping, and is often read as a pregnancy marker. Before this time, there is little contact between the developing embryo and the mother. Moreover, there is essentially no active/adaptive immune system in the embryo, as there is little cell differentiation. An allergic response requires mast cells or basophils.

After implantation, a placenta is formed. The placental barrier is selectively permeable, and uses active transport to move large molecules across the barrier. The molecules involved in active transport are very protein-specific, even to the point of rejecting similar immunoglobins, most notably IgE which activates the allergic response in mast cells and basophils.

(Rhesus incompatibility is a much more common problem and does more or less what you suggest: there can be a leakage of blood in the foetus->mother direction (ONLY!) that given an Rh+ foetus and an Rh- mother, can lead to an IgG response; immunoglobin G can cross the placental barrier and attack the Rh sites on the surfaces of foetal blood cells. Result: anaemia, jaundice, and possibly death of the foetus. Rhesus haemolytic disease was commonplace, but since the 70s an injection of passive antibodies (Rh immune globulin) into an Rh- mother quickly and throughly destroys Rh+ foetal blood cells before they can elicit an IgG response. Standard western postnatal care also involves administering RhIG to Rh- mothers after the birth of a child, to eliminate the risk of training her adaptive immune system with spillover blood from her baby (and the placenta. It is worth noting that the vast majority of sensitizing events in Rh haemolytic disease generally occur after the 28th week of pregnancy, and that the dangerous allergic response is that of the mother. So this does not really fit your hypothesis well at all.)

Some small molecules (like ethanol) cross the barrier via diffusion; some viral particles (like CMV) actively "tunnel" through the barrier in a variety of ways. These can be dangerous to even a young foetus.

Spontaneous abortions are sadly commonplace, and some studies using very sensitive early pregnancy tests show an incidence of 25% of fertilizations resulting in miscarriage before the 6th week.

A great deal of study has gone into early spontaneous abortions, and about half of the embryos studied have shown chromosomal aberrations including outright misarrangements. These are thought to be caused by a fertilization involving one or two damaged gametes, rather than a structural, repeatable genetic defect in either parent. These embryos stop developing on their own most of the time, and are sometimes called "blighted ova".

Obesity, use of NSAIDs, alcohol consumption and high caffeine intake are also associated with higher than average miscarriage rates.

It is certainly plausible that a response to an allergen by the mother could lead to an early spontaneous abortion. This has been seen in Rh haemolytic syndrome, and other allergic repsonses could similarly attack an implanted embryo with the mother's antibodies.

However, your hypothesis that young embryos might self-terminate in the face of an allergen is unlikely, largely because young embryos lack an active/adaptive immune system. Moreover, most of the allergens in question are highly unlikely to reach a young embryo at all because of physical disconnectedness or the filtering done by the placenta (and the rest of the mother's body too, which is an imposing physical barrier armed with its own immune system).

Finally, as noted, misc