To Head Off Allergies, Expose Your Kids to Pets and Dirt Early

[Guest guest]

To Head Off Allergies, Expose Your Kids to Pets and Dirt Early. Really.

www.intelihealth.com/IH/ihtIH/EMIHC251/333/21343/455934.html?d=dmtICNNews

(USA TODAY) -- Here's the conventional wisdom: Pets promote allergy,

kids shouldn't eat peanuts until they're at least 3, and intestinal worms

are nothing more than an icky reminder of life before flush toilets.

Here's the new wisdom: Early exposure to pets, peanuts and intestinal

worms might actually be good for you, because they program the developing

immune system to know the difference between real threats, such as germs,

and Aunt Millie's cat.

Evidence to support this view has been mounting for more than a

decade. But now, for the first time, researchers are beginning to test

remedies based on these theories in patients. Other doctors are trying to

make use of novel approaches to retrain the immune system once it's too late

and allergies set in.

" What we've learned is that it may, in fact, be important to be

exposed early on to a sufficient quantity of allergy-causing substances to

train the immune system that they are not a threat, " says Andy Saxon of the

University of California-Los Angeles. " And, in people who already have

allergies, we see for the first time where the problems lie, and we have new

opportunities to tweak the system. "

Scientists base this radical new thinking about human allergies on a

deeper understanding of how the immune system works. They have begun to

exploit fresh insights to attack allergies and other immune diseases in

unexpected ways. No longer content just to treat allergy symptoms, they hope

to outwit the immune system and stop allergic responses before they start.

" When you're born, Day Zero, your immune system is like a new

computer. It's not programmed. You have to add software, " says

Weinstock of Tufts New England Medical Center. " Between the ages of zero and

12, you're learning to read, you're learning to write, and your immune syste

m is learning to react to things. Part of that is learning to limit

reactivity. "

If the new approaches work, millions might benefit. More than

50million people have allergic diseases, which are the sixth-leading cause

of chronic illness in the USA, according to the National Institute of

Allergy and Infectious Diseases (NIAID), costing the health system $18

billion a year.

Asthma alone accounts for 500,000 hospitalizations a year, including 2

million admissions to the emergency room, says a study in the May 2005

Journal of Allergy and Clinical Immunology. Since 1980, adult asthma cases

have risen by 75% and childhood asthma by 160%, the Centers for Disease

Control and Prevention reports.

To test whether high-dose exposure breeds tolerance, researchers led

by Gideon Lack at Imperial College in London are preparing to launch a

counterintuitive -- and some would say risky -- seven-year, U.S.-financed

study that will expose infants to peanuts. It's based on research showing

that children who eat peanuts at an early age are less likely to develop

peanut allergies.

The study is risky because children with unrecognized peanut allergies

might suffer anaphylactic shock, a deadly drop in blood pressure often

combined with asthma, if they're exposed to peanuts.

A second team of researchers, led by Holt of the University of

Western Australia in Perth, will conduct a similar study in which children

who are already allergic to other substances will be exposed to airborne

allergens such as ragweed to see whether it will block the development of

other allergies.

Other studies suggest that short-lived infections with a benign

parasite might relieve allergies and possibly autoimmune illnesses such as

Crohn's disease and Type I diabetes by restoring the immune system's natural

balance. Major human trials in the USA and Europe are set to begin this

year.

Although trying to link allergies to autoimmune diseases such as

Crohn's might seem like a stretch, scientists say both types of ailments

result from an immune system run amok. In allergies, the immune system goes

on alert when ragweed or some other allergy-causing protein wafts through

the air, settles on the skin or tickles the tongue. In autoimmune diseases,

the immune system can no longer distinguish between the self and foreign

proteins. Mistaking the self for those proteins, the immune system attacks

the bowel in Crohn's disease or insulin-producing cells in Type 1 diabetes.

Early intervention

If educating the immune system is tough, re-educating it after

allergies set in appears to be tougher. Allergy shots work, but they're

costly and often must be continued for years, and the protection fades over

time. Higher-tech approaches rely heavily on 21st-century molecular medicine

to engineer proteins that block allergies.

One strategy, pioneered by researchers at Dynavax Technologies in

Berkeley, Calif., involves disguising a key ragweed protein with DNA from a

bacterium. The goal: to create a new short course of allergy shots that

tricks the immune system into permanently thinking that ragweed is a

bacterium, so it will attack it like a germ and not mount an allergic

response. The approach has appeared to work in early trials at s Hopkins

University.

A second strategy, now being developed by Saxon and his colleagues at

UCLA and licensed to the biotech firm Biogen Idec, involves fusing a cat

allergen with a snippet of a powerful antibody called IgG. This IgG snippet

turns off cells that make histamine, the chemical responsible for scratchy

throats, watery eyes, runny noses and asthma. Researchers hope the combo

will lock histamine-producing cells in the off position, and, in time,

retrain the immune system to accept that Aunt Millie's cat is harmless.

Hypothetically speaking

The new approach to allergy prevention and treatment arises from a

paradox. Known as the hygiene hypothesis, it suggests that growing up in

cities and suburbs, away from fields and farm animals, leaves people more

susceptible to a host of immune disorders, including allergies and asthma.

Weinstock says the divide between developed and undeveloped countries

is still evident today. " Hay fever is the most common allergy in the

developed world, " he says. " Yet, there are some countries in the world where

doctors don't know what hay fever is. "

What about urban life is triggering a rash of allergies and autoimmune

diseases? It's a good question, and not an easy one to answer. The immune

system isn't palpable as are the heart and lungs; you can't listen to it or

feel its pulse. Yet the immune system is our most sensitive link to the

environment, on alert for threats of all kinds, most of the time running in

the background like computer anti-virus software.

To accelerate the research, the National Institutes of Health and the

Juvenile Diabetes Research Foundation in 1999 set up a seven-year, $144

million international consortium called the Immune Tolerance Network, says

Marshall Plaut of NIAID. Already, research is turning up surprising results.

Dennis Ownby of the Medical College of Georgia followed 474 infants in

the Detroit area from birth to age 7, hoping to identify clues about why

some would pick up allergies and others would not. Ownby, then at Henry Ford

Hospital, says he was unprepared for what he found.

Ownby's team compared 184 children who were exposed to two or more

dogs or cats in their first year of life with 220 who didn't have pets. To

their surprise, the scientists found that children raised with pets were 45%

less likely to test positive for allergies than other kids. The study

appeared in the Aug. 28, 2002 Journal of the American Medical Association.

" We've been taught for at least a couple of decades that early

exposure to an allergen increases the risk of becoming allergic later in

life, " Ownby says. " So when we first examined our data, we were very afraid

that something had gone wrong. It's the opposite of what we would have

predicted. "

The challenge now, Ownby says, is to figure out what's happening. One

possible explanation is that dogs and cats shed a substance called

endotoxin, from bacteria. A study by Andy Liu of National Jewish Medical and

Research Center in Denver reported in 2000 that infants with the most

endotoxin exposure were the least likely to have allergies, indicating that

what researchers call the Pigpen Effect, the invisible cloud of dust and

dirt surrounding us all, might not be a bad thing.

Or consider the peanut paradox. In the past 10 years, peanut allergies

have doubled in the USA, United Kingdom and other countries that advise

against exposing unborn children to peanuts (through their mothers' diet)

and during infancy, Imperial College's Lack says. He believes children

become allergic to peanuts not by eating them but by coming into contact

with peanut oil in their mothers' skin lotions, according to a study

published in the March 2003 New England Journal of Medicine. Studies of

rodents suggest eating peanuts conditions the immune system to tolerate

them.

Infants in regions of Africa and Asia who are exposed to peanuts

rarely develop the allergy, Lack says, in contrast to countries such as the

USA and UK, where the prevalence of peanut allergies might be more than 10

times higher.

To test whether eating peanut products can protect children from

peanut allergies, Lack plans to launch a dramatic seven-year study in which

parents will regularly feed high doses of peanuts to about 200 children who

have egg allergies or eczema, conditions that put them at high risk of

developing other allergies. Parents of another 200 children will follow the

government's advice and try to completely avoid peanuts.

One key message, Lack says, is don't try this at home, without the

safeguards of a carefully controlled trial. " Feeding babies peanuts can be

extremely dangerous, " he says.

As high-risk as the trial is, it might be extremely rewarding, doctors

say. Each year in the USA, about 15,000 people suffer severe allergic

reactions from eating peanuts, and about 100 die.

" It's the first large-scale trial of what we consider a very dangerous

allergic food, " Ownby says.

To the squeamish, it might not matter that intestinal worms are less

risky than foods that promote allergy. But some doctors say worms might do

something that allergy-causing substances won't do -- broadly reset the

immune system so that it no longer reacts to allergy-causing substances or

attacks the body's tissues, as it does in Crohn's disease and Type I

diabetes. " This is an exciting new area with potential for opening new

therapeutic avenues for diseases that are hard to control and treat, " says

Weinstock of Tufts New England Medical Center.

Worms captured Weinstock's imagination and that of his collaborator,

Elliott of the University of Iowa, because worm infections appear to

regulate the immune system so that it functions normally. The allergic

response -- itchy, watery eyes, a runny nose and constriction of smooth

muscles -- evolved to flush out intestinal worms. " The immune system didn't

evolve for allergy, " Weinstock says. " Why in a hundred billion years of

evolution would we evolve a response for allergy? "

In fact, says Coffman, vice president of the biotech firm

Dynavax Technologies, the immune system developed two sets of responses: one

for bacteria and viruses and one for worms. Called Th1 for germs and Th2 for

worms, they work in opposition. When Th1 is active, Th2 takes a break. When

Th2 is active, it's Th1's turn. All of the symptoms people link with allergy

are part of the Th2 response.

The worm turns

Weinstock, Elliott and other researchers believe that a low-grade

infection with intestinal worms -- pig whipworms because they can't

reproduce in people -- can restore the immune system's natural balance. A

small-scale study in which 29 people with Crohn's disease drank whipworm

eggs in Gatorade found that 23 responded to treatment and 21 of the 23

experienced complete remission.

Although worms haven't been directly tested in allergic patients,

researchers point to a study by Yazdanbakhsh of Leiden University in

the Netherlands, which found that treating schoolchildren in Gabon for

worms, so that the worms were expelled from their bodies, doubled their risk

of becoming allergic to house dust mites, a common allergen.

Weinstock argues that it is exposure to the worms in the environment

that confers protection against allergies. " That's one possibility, " he

says. " Whether it's due to worms, endotoxin, lifestyle, smoking or other

factors that we haven't identified -- that's the fun of it. But environment

clearly plays a part. "