Since DS was 12 weeks early, spent enough time on oxygen to be diagnosed with chronic lung disease, and came home just in time for the start of the cold & flu season, we were ruthless about isolating him the first six months we had him at home.  No contact with anyone sick (we wore masks the one time we had colds), no contact with anyone who had kids or was around kids, jugs of Purell, no public excursions.  It worked; he didn't get sick all winter.

It was our ped's thought that if DS got sick now, it might not be so bad because he needed to build immunity.  So we stopped being careful about who he saw, stopped wiping everything he could touch with antibacterial cloths, didn't get too concerned the times he licked the bottom of a shoe.  Oh, and I'm not the most dedicated housekeeper.  I give him a bath about three times a week because he doesn't sweat or get very dirty.

He's 19 months now and has barely had a cold.  He's never had an ear infection.  He's around other kids, and granted, most of them are not in daycare, but we've been sick. My SIL, for example, makes her kids change clothes if they've been at a playground. She wipes off anything another kid might have touched before her kids can get to it. She scrubs her house, bathes her kids every night, and has gotten them into the habit of reaching for Purell when they're in public.  They are four and 20 months, and are each on their second or third set of ear tubes and are on & off antibiotics continuously. So I'm not sure what to think, but my observation so far has been maybe I've accidentally strengthened DS's immune system by letting him get exposed to stuff. I'm still knocking on wood though for his good health.

I have celiac disease, or at least, I'm pretty sure that if I had health insurance and could afford to prove that I had celiac disease, I would be shown to have it.

Anyway, yeah I would happily test out the worm theory, if it meant I could go near simple grains again without getting violently ill.  But I really don't know about the hygiene hypothesis.  For one thing, I am not exactly the goddess of domesticity.  My mother kept a very clean house, but I spent my early childhood running around outside, eating sand, trying out raw bird eggs, and generally doing every disgusting thing that a young child could think of.  Our house was pretty old and while it was kept very clean, we had pets and the sort of dust that just accumulates in old houses no matter what you do.

I don't know if I'm buying it, on the individual level, because the people I know who are prone to allergies aren't necessarily the people I know who live in the cleanest houses.  Sometimes quite the opposite.  I think it must be more complicated than that.

The beauty of the immune system is that it is designed to create a highly specific response to just about anything, no matter what it looks like.  The only thing it never expected was to see nothing at all.  So it's not programmed to handle that - it keeps looking for a hidden enemy that must be around.  And attacks it's best guesses.

Some suggest it is the timing of exposures relative to the stage of development that is important here.  The immune system is very immature at birth are undergoes a great deal of development during the first year.  By protecting babies from germs until they're 'old enough' to deal with illnesses, it may be that we're actually missing the window of opportunity for training the immune system.  Of course the infant immune system continues to develop with or without challenge, but it was never designed for a germ free environment.

I was never very good at immunology even back when I remembered what I studied, but I think the immune system is relatively mature by the end of the first (or was it second?) year.  So once our kids are past toddlerhood our hygiene practices may not matter all that much.  I'm sure there must be studies on this going on somewhere.

is the role of our intestinal flora in our health and welfare.

Just to start, you actually have more cells of bacteria - non-human DNA - in your gut than you have human cells in your whole body.

So doesn't it then seem likely that the particular ratios of different species inside your gut would make a difference in your digestion, which then might be part of your overall health? After all, if you can't absorb, say, B-12, you're going to be deficient. Those bacteria are critical for digesting certain molecules, and so, it seems extremely plausible that a calorie is not the same for all humans - some people will get more energy from the same exact food than another person will, because of the intestinal flora.

So worms sound nasty - and who knows exactly how they work - but if they do, it would be great.

and my folks always had at least a dog and a cat (usually more) and I was raised without air conditioning in Florida! Mildew, mold, dust all in the house.

My Best Friend also has terrible (nearly life threatening) allergies to dust, cats, stuff and he was raised on a farm in New Hampshire.

If they can isolate what it is exacly in n let my the environment that he and I somehow missed I would yake in in a flat minute. I can't even let my little girl have a cat because I'd have to move out! Sigh.

I get the hygiene hypothesis, but I'm a bigger believer that immune diseases have some sort of genetic basis, however complicated.  

On exposing babies in their first year, I really don't get that.  They will get exposed just by being around any people.  On the flip side, RSV can be so dangerous to an infant, so keeping infants away from sick people seems wise.