Paging Jeanne (dogmom) re food introduction/allergies

[COElizabeth]

Jeanne,

Your interesting comments on the vaccination thread (I agree with you on the importance of basing these decisions on good research, and I thought your comments on the Hep B vaccination timing were good food for thought, too, by the way) reminded me that I wanted to ask you about what you had found out re timing of food introduction and allergies. Were you the one who said she was going to try to do some research to find out whether there is any hard evidence that delaying nuts or eggs or whatever until a certain age decreases the risk of allergy? I hear that exposure to dog hair early on, for example, decreases the risk of allergies later, but that avoiding peanuts until 3 or 5 or whenever decreases the risk of allergy. The idea that early exposure contributes to allergy for some substances but prevents it for others seems counterintuitive (though it could certainly be true, and I realize that dog hair isn't eaten in large quantities by most children - though James has certainly had a fair amount!). Did you ever find anything interesting? If you weren't the one who posted, I apologize!

Elizabeth, Mom to James, 9-20-02

[egoldber]

Elizabeth, I can't point to specific research, but I just heard a discussion of this on NPR a week or so ago. The topic was food allergies and there was a pediatrician and an allergist on the program. They were discussing various food allergies and reiterated what I have heard about delaying peanuts and tree buts until age 3. And recommending that pregnant and nursing moms with a family history of allergies shoud avoid peanut and tree nuts as well.

But I agree that it is counterintuitive to the other info out there about early exposure to allergens preventing some allergies and also asthma.

[KathyO]

This subject is a biggie, and it's one of my particular obsessions, so I warn y'all... the following will be long and boring!

The short answer to your question is that most allergic sensitization, particularly for the violent, life-threatening allergies (peanuts, seafood, etc.) happens very early in life. So if you can prevent the system from encountering the allergen during this period, the sensitization cannot take place, or you can at least cut down the severity of the allergy when it DOES take place later on. There is lots of hard evidence showing that delaying the introduction of certain foodstuffs cuts down on the incidence of allergy, and on the incidence of severe allergy in particular.

If a baby is at particular risk for violent allergy (ie. Mom or Dad has a violent allergy), then Mom is often advised to go one step further and not consume any major allergens (nuts, eggs, shellfish, etc.) during pregnancy and nursing, to eliminate the chance that a stray molecule of the substance will sneak across the placenta or into the breastmilk where the infant's system can get exposed to and sensitized to it.

Your question on where dog hair fits in is a good one. Because the immune system (particularly the developing immune system) is so fiendishly complex, science has only been able to decode parts of it. Large chunks are kind of a black box. "We don't know exactly WHY it works this way, but we have consistently shown that THIS factor seems to promote THAT outcome." And the number of factors that seem to be at work mean that there is no one "smoking gun" for causing allergies. There seem to be a whole bunch of smaller contributing factors. As noted above, heredity is one, but only one.

As far as anyone can tell, early exposure to pets seems to roll in with the "Hygiene Hypothesis". In a nutshell, the infant's immune system arrives in the world geared up to fight all comers in what has always been a very germy world. Because we have eliminated many major sources of infection in our culture, the system goes looking for a fight, and basically picks on things which are really not enemies at all (nut proteins, latex, you name it). Presto - an allergy. (Okay, there's more to it than that, but I want you bored - not comatose!!) Supporting this model are a multitude of reputable studies showing lower rates of allergy in children who: are exposed to other kids and their germs in day care, have older siblings to bring the germs home, live on livestock farms, have multiple upper-respiratory infections early in life, are not given broad-spectrum antibiotics early in life, suffer childhood parasitic infections, are exposed to rubella, chickenpox and/or tuberculosis early in life, et cetera. (Note: This is what the data shows. It does NOT mean that I advocate exposing kids to tuberculosis or parasites!!!) Exposure to dogs and cats early in life is thought to come in under the "living with livestock" category. Basically, it broadens the spectrum of germs you get exposed to. And broad germ exposure means a system that is too busy dealing with germs to go looking for trouble.

So, does that answer anything or have I muddied the issue further? If you are REALLY in a masochistic mood, ask me about colonization with the correct gut bacteria early in life... this is a whole realm of research that is showing some fascinating connections to development of early food allergies. Well, fascinating to me...:P

Cheers,

KathyO

Obsessive-compulsive-for-hire

[Rachels]

Me too!!! Tell me, tell me!

-Rachel
Mom to Abigail Rose
5/18/02

[COElizabeth]

Oh, yes, I AM interested in the gut bacteria topic, too! :)

I don't really want to bring parasites into the house, but I have been sort of hoping that just plain dirt might help build his immune system. At least, that's what I say to justify delaying mopping another day!

Elizabeth, Mom to James, 9-20-02

[KMommie]

Thanks for the good info! Very interesting and fascinating...I'll be printing out your explanation to give to my DH and ILs to help them understand WHY I'm being so careful with Kiki.

Jeannie
mommy to Kiki 4/18/03

[stillplayswithbarbies]

I was looking up something else and came across this article, which touches on this subject about how exposing baby to certain foods too early can cause allergies:

http://www.kellymom.com/nutrition/solids/delay-solids.html

It's partway down, where it talks about the "open gut".

...Karen
Jacob Nathaniel Feb 91
Logan Elizabeth Mar 03

[KathyO]

Hi again - apologies to anyone I've kept waiting... my sister is the Infection Control Practitioner for the local hospital, and needed help on a whack of last-minute presentations for all staff on the top infection control issues for the upcoming year. Fun fun fun. On the bright side, though, I have learned from this that the World Health Organization has concluded that SARS is not really an issue for children; out of some 8,400 cases worldwide, only TWO involved children contracting SARS from an adult, and there were NONE where a child got it from another child, or from its infected mother while in utero. So - even if it returns this year, it will not be rampaging through the schools. Current theories suggest that children are not immune to SARS; it just shows up as a transitory low-level cold that comes and goes without being remarked on.

Anyway, back to allergies! Just to lay a bit of background... consider the intestines. You may think of your skin as being the main barrier that protects you from the hostile germs and such in your world. And it does. But the surface area of the adult gut is close to that of a full-size tennis court, and unlike the skin, it has to do more than just repel invaders. It has to constantly pass nutrients INTO the bloodstream/system, wastes OUT of the bloodstream/system, and it has to simultaneously prevent bad microbes from crossing in via that same border that the nutrients come in through. Your immune system has evolved a host of incredibly complex interacting mechanisms to distinguish good stuff from bad stuff, and to bring in the good stuff while killing/repelling the bad stuff. Imagine a gigantic border/customs/immigration clearinghouse, with inspectors, record-keepers, guards, porters, soldiers, and traffic controllers all doing their separate jobs simultaneously.

Okay. This is where things get a bit fuzzy, because science is only just beginning to unravel how this all gets set up. But they DO know that one critical element to the whole system is the beneficial bacteria that live in your gut - various strains of Lactobaccillus and Bifidobacterium. They do lots of things that we know about, and many that we don't. They help stimulate the maturation of the appropriate ratios of immune cells and mechanisms in the gut. This is critical, because allergies are fundamentally an IMBALANCE in the makeup your immune system, with one type of T cells strongly dominant over the others. These bacteria also pre-digest many proteins, so that they cannot enter your bloodstream whole, where they can be recognized as an allergen and reacted to. They engineer physically observable differences in the gut environment, so that if they get flushed out by diarrhea (or antibiotics), the environment is more hospitable to THEM returning, than to other organisms.

How do they get in there in the first place? Breastmilk helps as a "prebiotic", by filling the gut with substances conducive to the growth of the right germs. If your mom's gut is colonized with the correct bugs, you'll pick them up from her skin, and from her milk and even her birth canal (which makes use of the same germs as part of its defence system). Later in life, consumption of live-culture yogurts has a measurable effect on encouraging correct colonization, as do certain other foodstuffs (like unpasteurized milk... although this carries a whole separate set of risks as well, which we won't go into right now.)

How does allergy enter into it? Well, it has been shown that when less-desirable microbes (staphylococcus and enterococci, among others) elbow their way into the infant gut first, and crowd out the ones you really want, particularly in the first year or so of life, there is a significantly higher risk of allergy and asthma later in life, because the good critters are not in their doing their job of breaking down allergens and encouraging properly balanced immune system development. One research project found that all subjects they studied who had severe allergies had observable differences in their gut microbe populations from non-allergic people, who had the right mix of "good bugs".

The same researchers went further, and took a large cohort of mothers who were at high risk of having allergic babies. The mothers were given daily doses of Lactobacillus rhamnosus GG (a big player in the good-bug gang) for six weeks before due date, to get their systems properly colonized. After birth, moms with breastfed babies continued taking the supplement for a period; bottlefeeding moms put a baby-sized supplement of the same stuff in the bottles for the same period. Result: half the rate of allergic disease in the Lactobacillus group babies as in the control group babies.

So, what factors can interfere with the correct colonization taking place? Several well-designed studies have shown that infants who receive antibiotics in the first six months of life are at significantly increased risk of allergy and ashthma. The antibiotics wipe out the good bugs along with the bad ones (as those of you who have ever gotten a post-antibiotic yeast infection already know), and screw up the re-establishment of the good ones. Give the child broad-spectrum antibiotics in this period and the risk jumps even higher. I personally have wondered if the practice of giving antibiotics to moms who have Group B Strep may be contributing to the same effect, but I have no data to back that up.

C-section infants have been shown to be at a slightly higher risk; the theory is that they don't get exposed to mom's vaginal flora during birth, and frequently don't get to spend close time with mom right away; this increases the chance of the bad bugs getting in there first and establishing a foothold.

Breastmilk seems to have a positive effect, both by favouring the development of "good bugs" and providing a broad spectrum of antibodies to the bad ones, plus the food it provides has already been "filtered" by mom's mature gut, but the studies have been exasperatingly inconclusive, because so few have tried to control for all the other known factors, let alone the as-yet-unknown ones.

Where does delayed food-introduction fit in here? Well, the older you are when you receive the food, the more likely your gut microbes are well established and able to do their jobs. And the more likely that your own digestive system is properly established and able to distinguish true enemies from false ones.

And I should emphasize again, as before -- the immune system is so full of switches and levers that there appears to be no one single cause for allergic disease. So there will be children exposed to all the risk factors listed above who still don't develop allergies, and children with none of the known risks who DO. There's a whole mess of factors at work -- and that's just the ones we currently KNOW about!!

Rats - someone is awake and wailing upstairs... I may come back and modify this later, but I hope it'll do the job in the meantime. Apologies to the folks I have doubtless bored the pants off of!!

KathyO

P.S. - I get my data from obsessively reading publications like The Lancet and New England Journal of Medicine. If you're curious about a particular point, let me know and I can probably point you to the source studies pretty promptly, but if I've given birth in the meantime all bets are off!

[Karenn]

Wow. That was so thorough! I'm impressed. Thanks so much for taking the time to explain all that! I, for one, found it very interesting and not boring at all. I think I might even know more about allergies than my pediatrician at this point! It's interesting to me that I introduced milk and wheat to Colin shortly after he finished his first ever round of antibiotics. Those are the two foods he seems to have trouble with. The wheels are now turning in my head. Thanks!

[KMommie]

Wow! Thanks so much for taking the time to write out all this info! Now, I'm really wondering about that ped who told me to start solids when we were starting our second round of antibiotics to "help" DD with her diarrhea. And, I'm so glad that I didn't listen to him!

Thanks for sharing your knowledge...

Jeannie
mommy to Kiki 4/18/03

[KathyO]

Good call -'m not sure I would have made the right decision without all this reading. But, just an item of interest that works in with all the stuff above... one of the studies I read, which has now been translated into standard practice at the hospital involved, is to give probiotics ("good bugs", but I don't remember exactly which strains at the moment) to infants suffering from antibiotic-related diarrhea, or clostridium difficile (a "bad bug")-related diarrhea. The treatment consistently eliminated the diarrhea, and had the unexpected side benefit of reducing diarrhea-related diaper rash in these kids as well.

So much more to find out...

Cheers,

KathyO