Skip to content

 More research supports that being exposed to pets during pregnancy or in the first months of life changes the gut bacteria, and in a way that is thought to be beneficial. The researchers found that infants exposed to pets prenatally or after birth (or both) had higher levels of two microbes that are associated with a lower risk of allergies and obesity. The two microbes are Ruminococcus and Oscillospira, but in case you're wondering - they are not (yet) available in probiotics.

And these differences in gut bacteria occurred no matter how the infants were born or fed (C-section, vaginal, breastfed, formula fed), or whether they received antibiotics at birth or not  - it was the pet exposure that was most important. The evidence is building that if one wants to avoid allergies in children - to have them exposed to furry pets in the first  year of life, and according to this study - perhaps before birth also. From Science Daily:

Pet exposure may reduce allergy and obesity

A new University of Alberta study showed that babies from families with pets -- 70 per cent of which were dogs -- showed higher levels of two types of microbes associated with lower risks of allergic disease and obesity.

"There's definitely a critical window of time when gut immunity and microbes co-develop, and when disruptions to the process result in changes to gut immunity," said Anita Kozyrskyj, a U of A pediatric epidemiologist....The latest findings from Kozyrskyj and her team's work on fecal samples collected from infants registered in the Canadian Healthy Infant Longitudinal Development study build on two decades of research that show children who grow up with dogs have lower rates of asthma

Her team of 12, including study co-author and U of A post-doctoral fellow Hein Min Tun, take the science one step closer to understanding the connection by identifying that exposure to pets in the womb or up to three months after birth increases the abundance of two bacteria, Ruminococcus and Oscillospira, which have been linked with reduced childhood allergies and obesity, respectively.

"The abundance of these two bacteria were increased twofold when there was a pet in the house," said Kozyrskyj, adding that the pet exposure was shown to affect the gut microbiome indirectly -- from dog to mother to unborn baby -- during pregnancy as well as during the first three months of the baby's life. In other words, even if the dog had been given away for adoption just before the woman gave birth, the healthy microbiome exchange could still take place.

The study also showed that the immunity-boosting exchange occurred even in three birth scenarios known for reducing immunity, as shown in Kozyrskyj's previous work: C-section versus vaginal delivery, antibiotics during birth and lack of breastfeeding. What's more, Kozyrskyj's study suggested that the presence of pets in the house reduced the likelihood of the transmission of vaginal GBS (group B Strep) during birth, which causes pneumonia in newborns and is prevented by giving mothers antibiotics during delivery. [Original study.]

Image result for maple tree allergies Could this be true? Probiotics for seasonal allergies? A study by Univ. of Florida researchers reported that taking a combination probiotic of Lactobacillus gasseri, Bifidobacterium bifidum, and Bifidobacterium longum (sold as Kyo-Dophilus) for 8 weeks during spring allergy season resulted in an improvement in seasonal allergy symptoms. It must be noted that the people participating had mild seasonal allergies, not severe allergies. While they reported overall allergy symptom improvement, there was no significant improvement with eye symptoms. Too bad, because for those suffering from itchy eyes, it is a symptom that causes anguish during allergy season.

All participants had their stool (fecal) samples tested (with modern genetic sequencing) and it was found that the group taking the probiotic supplements had a beneficial shift in their overall microorganisms in the gut - with some bacteria such as Escherichia coli decreasing and the very beneficial and anti-inflammatory bacteria Faecalibacterium prausnitzii increasing. (See posts here and here on F. prausnitzii.) What was really good about the study was that it was a "double-blind, randomized clinical trial", meaning that people were randomly  assigned to the probiotic treatment or placebo group, and no one knew who was getting a placebo or the probiotic until the end of the study. The researchers say that why the probiotics improved allergy symptoms is s till not clear, but they have some theories. From Science Daily:

Allergies? Probiotic combination may curb your symptoms, new study finds

As we head into allergy season, you may feel less likely to grab a hanky and sneeze. That's because new University of Florida research shows a probiotic combination might help reduce hay fever symptoms, if it's taken during allergy season. Many published studies have shown a probiotic's ability to regulate the body's immune response to allergies, but not all of the probiotics show a benefit, UF researchers say. Scientists already know that the probiotic combination of lactobacilli and bifidobacteria, sold as Kyo-Dophilus in stores, helps maintain digestive health and parts of the immune system. They suspect that probiotics might work by increasing the human body's percentage of regulatory T-cells, which in turn might increase tolerance to hay fever symptoms.

UF researchers wanted to know if the components in this combination probiotic would help alleviate allergy symptoms. To do that, they enrolled 173 healthy adults who said they suffered seasonal allergies and randomly split them into two groups: Some took the combination probiotic; others took a placebo. Each week during the eight-week experiment, participants responded to an online survey to convey their discomfort level. Scientists also analyzed DNA from participants' stool samples to determine how their bacteria changed, because probiotics aim to deliver good bacteria to the human's intestinal system.

Participants who took the probiotic reported improvements in quality of life, compared to those taking the placebo, the study showed. For example, participants suffered fewer allergy-related nose symptoms, which meant that they were less troubled during daily activities. Researchers note that this study did not include severe allergy sufferers. But the combination of probiotics showed clinical benefit for those with more mild seasonal allergies, Langkamp-Henken said. [Original study.]

 Earlier posts discussed research that showed that farm and animal (pets such as dogs) exposures in the first year of life is protective against allergies and asthma (lowers the risk of developing them). New research examined this further by looking at Amish and Hutterite groups - looking at not just "farm life", but whether children had much exposure to farm animals. The Amish have close exposure to farm animals (traditional farming methods), but the Hutterites don't (communal highly industrialized farming). Both groups studied had similar lifestyles (drank raw milk, breastfeeding, little exposure to smoking), but both groups did not have indoor pets ("taboos against indoor pets"). Thus farming methods were important for exposures to animals and their microbes.

The researchers said: "The importance of environmental exposures in the development of asthma is most exquisitely illustrated by epidemiologic studies conducted in Central Europe that show significant protection from asthma and allergic disease in children raised on traditional dairy farms. In particular, children’s contact with farm animals and the associated high microbial exposures4,5have been related to the reduced risk." Traditional farming exposed the children to an environment rich in microbes, and these children had very low rates of asthma and "distinct immune profiles that suggest profound effects on innate immunity." Once again, note the importance of microbes in the development of the immune system. From Science Daily:

Growing up on an Amish farm protects children against asthma by reprogramming immune cells

By probing the differences between two farming communities -- the Amish of Indiana and the Hutterites of South Dakota -- an interdisciplinary team of researchers found that specific aspects of the Amish environment are associated with changes to immune cells that appear to protect children from developing asthma. In the Aug. 4, 2016, issue of The New England Journal of Medicine, the researchers showed that substances in the house dust from Amish, but not Hutterite, homes were able to engage and shape the innate immune system (the body's front-line response to most microbes) in young Amish children in ways that may suppress pathologic responses leading to allergic asthma.

The Amish and Hutterite farming communities in the United States, founded by immigrants from Central Europe in the 18th and 19th centuries, respectively, provide textbook opportunities for such comparative studies. The Amish and the Hutterites have similar genetic ancestry. They share similar lifestyles and customs, such as no television and a Germanic farming diet. They have large families, get childhood vaccinations, breastfeed their children, drink raw milk and don't allow indoor pets.

The communities, however, are distinct in two important ways. Although both groups depend on agriculture, their farming practices differ. The Amish have retained traditional methods. They live on single-family dairy farms and rely on horses for fieldwork and transportation. In contrast, the Hutterites live on large communal farms. They use modern, industrialized farm machinery. This distances young Hutterite children from the constant daily exposure to farm animals. The other striking difference is what Ober calls a "whopping disparity in asthma." About 5 percent of Amish schoolchildren aged 6 to 14 have asthma. This is about half of the U.S. average (10.3%) for children aged 5 to 14, and one-fourth of the prevalence (21.3%) among Hutterite children.

To understand this disparity, the researchers studied 30 Amish children 7 to 14 years old, and 30 age-matched Hutterite children. They scrutinized the children's genetic profiles, which confirmed the remarkable similarities between Amish and Hutterite children. They compared the types of immune cells in the children's blood, collected airborne dust from Amish and Hutterite homes and measured the microbial load in homes in both communities.

The first gee-whiz moment came from the blood studies. These revealed startling differences between the innate immune response from the Amish and Hutterites. "The Amish had more and younger neutrophils, blood cells crucial to fight infections, and fewer eosinophils, blood cells that promote allergic inflammation," said study co-author, immunologist Anne Sperling, PhD, associate professor of medicine at the University of Chicago. Gene expression profiles in blood cells also revealed enhanced activation of key innate immunity genes in Amish children.

The second eureka moment came from experiments using mice. When study co-author, immunologist Donata Vercelli, MD, professor of cellular and molecular medicine and associate director of the Asthma and Airway Disease Research Center at the University of Arizona, exposed mice to house-dust extracts, she found the airways of mice that received Amish dust were protected from asthma-like responses to allergens. In contrast, mice exposed to Hutterite house dust were not protected.

What was different? Dust collected from Amish homes was "much richer in microbial products," the authors note, than dust from Hutterite homes. "Neither the Amish nor the Hutterites have dirty homes," Ober explained. "Both are tidy. The Amish barns, however, are much closer to their homes. Their children run in and out of them, often barefoot, all day long. There's no obvious dirt in the Amish homes, no lapse of cleanliness. It's just in the air, and in the dust."

To better understand how asthma protection was achieved, the researchers used mice that lack MyD88 and Trif, genes crucial for innate immune responses. In these mice, the protective effect of the Amish dust was completely lost. "The results of the mouse experiments conclusively prove that products from the Amish environment are sufficient to confer protection from asthma, and highlight the novel, central role that innate immunity plays in directing this process," Vercelli said.

 Newly published research found that children who are thumb-suckers or nail-biters are less likely to develop atopic sensitization or allergic sensitivities (as measured by positive skin-prick tests to common allergens). And, if they have both 'habits', they are even less likely to be allergic to such things as house dust mites, grass, cats, dogs, horses, wool, or airborne fungi. The finding emerges from a longitudinal study which followed the progress of 1,037 persons born in Dunedin, New Zealand in 1972-1973 from childhood into adulthood. However, the researchers found no relationship to these 2 habits to allergic asthma or "hay fever" - a contradictory finding that the researchers don't have an answer for.

"Our findings are consistent with the hygiene theory that early exposure to dirt or germs reduces the risk of developing allergies," said Professor Sears (one of the researchers).  The researchers were testing the idea that the common childhood habits of thumb-sucking and nail-biting would increase microbial exposures, affecting the immune system and reducing the development of allergic reactions also known as atopic sensitization. 31% of the children were frequent thumb suckers or nail biters.

Among all children at 13 years old, 45% showed atopic sensitization, but among those with no habits 49% had allergic sensitization; and those with one oral habit - 40% had allergic sensitization. Among those with both habits, only 31% had allergic sensitization. This trend continued into adulthood, and showed no difference depending on smoking in the household, ownership of cats or dogs; or exposure to house dust mites.

Excerpts of the study from Pediatrics: Thumb-Sucking, Nail-Biting, and Atopic Sensitization, Asthma, and Hay Fever

The hygiene hypothesis suggests that early-life exposure to microbial organisms reduces the risk of developing allergies. Thumb-sucking and nail-biting are common childhood habits that may increase microbial exposures. We tested the hypothesis that children who suck their thumbs or bite their nails have a lower risk of developing atopy, asthma, and hay fever in a population-based birth cohort followed to adulthood. Parents reported children’s thumb-sucking and nail-biting habits when their children were ages 5, 7, 9, and 11 years. Atopic sensitization was defined as a positive skin-prick test (≥2-mm weal) to ≥1 common allergen at 13 and 32 years. 

Thirty-one percent of children were frequent thumb-suckers or nail-biters at ≥1 of the ages. These children had a lower risk of atopic sensitization at age 13 years  and age 32 years. These associations persisted when adjusted for multiple confounding factors. Children who had both habits had a lower risk of atopic sensitization than those who had only 1. No associations were found for nail-biting, thumb-sucking, and asthma or hay fever at either age.

What This Study Adds: Children who sucked their thumbs or bit their nails between ages 5 and 11 years were less likely to have atopic sensitization at age 13. This reduced risk persisted until adulthood. There was no association with asthma or hay fever.

The “hygiene hypothesis” was suggested by Strachan1 to explain why children from larger families and those with older siblings are less likely to develop hay fever. Strahan hypothesized that this could be explained if “allergic diseases were prevented by infection in early childhood transmitted by unhygienic contact with older siblings, or acquired prenatally from a mother infected by contact with her older children.” The hypothesis is supported by evidence showing that children who grow up in large families are at greater risk of coming into contact with more infections....The hygiene hypothesis remains controversial, however, as it is unable to fully explain many associations, including the rise of allergies in “unhygienic” inner-city environments, and why probiotics are ineffective at preventing allergic diseases.3

Thumb-sucking and nail-biting are common oral habits among children, although the reported prevalence varies widely, from <1% to 25%.47 These habits have the potential to increase the exposure to environmental microorganisms, and have been associated with the oral carriage of Enterobacteriaceae, such as Escherichia coli and intestinal parasite infections.812 It seems likely that thumb-sucking and nail-biting would introduce a wide variety of microbes into the body, thus increasing the diversity of the child’s microbiome. If the hygiene hypothesis is correct, it is plausible that this would influence the risk for allergies.... 

Of 1013 children providing data, 317 (31%) had ≥1 oral habit: there was no significant sex difference in prevalence of these habits. Of the 724 children who had skin-prick tests at age 13 years, 328 (45%) showed atopic sensitization. The prevalence of sensitization was lower among children who had an oral habit (38%) compared with those who did not (49%) (P = .009). The lower risk of atopic sensitization was similar for thumb-sucking and nail-biting. Children with only 1 habit were less likely to be atopic (40%) than children with no habit at all (49%), but those with both habits had the lowest prevalence of sensitization (31%) .

Labrador Retriever image Other studies have found this same association - that living with a dog or farm animal has health benefits such as lower risk of allergies and asthma. In a Swedish nationwide study looking at over a million children, the association between early exposure to dogs and farm animals and the risk of asthma was evaluated. All children born in Sweden from January 1, 2001, to December 31, 2010 were included. The researchers found that exposure to dogs and farm animals during the first year of life reduces the risk of asthma in children at age 6 years. From Science Daily:

Early contact with dogs linked to lower risk of asthma

A team of Swedish scientists have used national register information in more than one million Swedish children to study the association of early life contact with dogs and subsequent development of asthma. This question has been studied extensively previously, but conclusive findings have been lacking. The new study showed that children who grew up with dogs had about 15 percent less asthma than children without dogs.

A total of more than one million children were included in the researchers' study linking together nine different national data sources, including two dog ownership registers not previously used for medical research...."Earlier studies have shown that growing up on a farm reduces a child's risk of asthma to about half. We wanted to see if this relationship also was true also for children growing up with dogs in their homes. Our results confirmed the farming effect, and we also saw that children who grew up with dogs had about 15 percent less asthma than children without dogs.

"These kind of epidemiological studies look for associations in large populations but do not provide answers on whether and how animals could protect children from developing asthma. We know that children with established allergy to cats or dogs should avoid them, but our results also indicate that children who grow up with dogs have reduced risks of asthma later in life. Thanks to the population-based design, our results are generalizable to the Swedish population, and probably also to other European populations with similar culture regarding pet ownership and farming" says Catarina Almqvist Malmros, senior author on the study, Paediatrician at Astrid Lindgren Children's Hospital and Professor in Clinical epidemiology at Dept of Medical Epidemiology and Biostatistics at Karolinska Institutet, Stockholm.

 Image result for toddlers  An interesting Canadian study that followed young children for 3 years found that young infants may be more likely to develop allergic asthma if they lack four beneficial bacteria in their gut. Children with low levels of Lachnospira, VeillonellaFaecalibacterium, and Rothia bacteria in their gut in their first 3 months were at higher risk for asthma and tended to receive more antibiotics than healthier children before they turned 1 year old.

Other studies have shown that the risk of developing asthma and allergies has been linked with such things as taking antibiotics, cesarean birth, bottle fed with formula, not living on a farm, and not having furry pets in the first year of life.

The researchers wrote: "Our findings indicate that in humans, the first 100 days of life represent an early-life critical window in which gut microbial dysbiosis {the microbial community being out of whack} is linked to the risk of asthma and allergic disease." How do the infants get these microbes? It is thought that infants get exposed to the mother's microbiome (microbial community) via vaginal birth, breast-milk, and mouth contact with the mother's skin.  From NPR News:

Missing Microbes Provide Clues About Asthma Risk

The composition of the microbes living in babies' guts appears to play a role in whether the children develop asthma later on, researchers reported Wednesday. The researchers sampled the microbes living in the digestive tracts of 319 babies, and followed up on the children to see if there was a relationship between their microbes and their risk for the breathing disorder. In the journal Science Translational Medicine, the researchers report Wednesday that those who had low levels of four bacteria were more likely to develop asthma by the time they were 3-years-old.

Specifically, the researchers focused on 22 children who showed early signs of asthma, such as wheezing, when they were 1-year-old. They were much more likely than the other children to have had low levels of the four bacteria when they were 3-months-old. By the time they turned 3, most had developed full-blown asthma."The bottom line is that if you have these four microbes in high levels you have a very low risk of getting asthma," says Brett Finlay, a microbiologist at the University of British Columbia who helped conduct the research. "If you don't have these four microbes or low levels of these microbes you have a much greater chance of asthma."

Asthma is a common and growing problem among children. Evidence has been accumulating that one reason may be a disruption in the healthful microbes children get early in life, Finlay says."There's all these smoking guns like, for example, if you breast-feed versus bottle feed you have less asthma," he says. "If you're born by C-section instead of vaginal birth you have a 20 percent higher rate of asthma. If you get antibiotics in the first year of life you have more asthma." The microbiomes of kids who aren't breast-fed and are born by Caesarean section may miss out on getting helpful bugs. Antibiotics can kill off the good bacteria that seem important for the development of healthy immune systems.

"What's become clear recently is that microbes play a major role in shaping how the immune system develops. And asthma is really an immune allergic-type reaction in the lungs," Finlay says. "And so our best guess is the way these microbes are working is they are influencing how our immune system is shaped really early in life."

To further test their theory, the researchers gave laboratory mice bred to have a condition resembling asthma in humans the four missing microbes. The intervention reduced the signs of levels of inflammation in their lungs, which is a risk factor for developing asthma.

The bacteria are from four genuses: Lachnospira, Veillonella, Faecalibacterium and Rothia. The researchers aren't exactly sure how the microbes may protect against asthma. But babies with few or none of them had low levels of a substance known as acetate, which is believed to be involved with regulating the immune system.

Image result for faecalibacterium prausnitzii  Faecalibacterium prausnitzii - a beneficial gut bacteria. Credit:News Press Agency

  It's official - the medical community has accepted that a key element in preventing allergies and asthma is early childhood exposure to allergens - whether peanuts, dust, or pets. Instead of avoiding the allergens (which was the medical advice for decades) - getting early exposure to them is key to preventing allergies. Apparently growing up on a farm is best (with exposure to farm dirt and dust), especially a dairy farm with animals and raw milk (a number of studies have found that unprocessed raw milk and its microbes also helps health). But if one doesn't live on a farm, then having furry pets in early childhood is also beneficial in reducing the incidence of allergies. The following study shows that microbes are involved - pet microbes were found in the guts of many of those children who did not develop early allergies! From Medscape:

Furry Pets 'Enrich' Gut Bacteria of Infants at Risk for Allergies

In a small, preliminary study, infants in households with furry pets were found to share some of the animals' gut bacteria - possibly explaining why early animal exposure may protect against some allergies, researchers say. The infants' mothers had a history of allergy, so the babies were at increased risk. It was once thought that pets might be a trigger for allergies in such children, the authors pointed out online September 3 in the Journal of Allergy and Clinical Immunology.

"Earlier it was thought that exposure to pets early in childhood was a risk factor for developing allergic disease," coauthor Dr. Merja Nermes, of the University of Turku in Finland, told Reuters Health by email. "Later epidemiologic studies have given contradictory results and even suggested that early exposure to pets may be protective against allergies, though the mechanisms of this protective effect have remained elusive."Adding pet microbes to the infant intestinal biome may strengthen the immune system, she said.

From participants in an ongoing probiotic study of pregnant women with a history of allergies, Nermes and her colleagues selected 51 infants of families with furry pets (dogs, cats or rabbits) in the home and 64 infants with no pet in the home. Fecal samples collected from diapers when the babies were one month of age were tested for the DNA of two types of Bifidobacteria that are found specifically in animal guts: B. thermophilum and B. pseudolongum. One-third of infants from the pet-exposed group had animal-specific bifidobacteria in their fecal samples, compared to 14% of controls. It's not clear where the infants without furry pets at home acquired the bacteria, the authors wrote.

When the babies were six months old they had skin prick tests to assess allergies to cow's milk, egg white, flours, cod, soybeans, birch, grasses, cat, dog, potato, banana, and other allergens. Nineteen infants had reactions to at least one of the allergens tested. None of these infants had B. thermophilum in their fecal samples.

Past research has linked growing up on a farm or exposure to dog dander indoors with protection against airway allergens, the study team wrote. Other studies have found increased "richness and diversity" in the gut microbes of kids exposed to household pets."When infants and furry pets live in close contact in the same household, transfer of microbiota between pets and infants occurs," Nermes said. "Human-specific Bifidobacteria have beneficial health effects, and animal-specific strains may also be beneficial, she said. It is still unclear, however, if exposure to these bacteria protects against allergies later in life, she said. 

Other researchers point out that the dirty farm dust may trigger low level inflammation in the lungs of young children which is somehow protective (and prevents allergies and asthma from happening). Go to the link for more details on the study. From Science Magazine: Dirty farm air may ward off asthma in children

For researchers trying to untangle the roots of the current epidemic of asthma, one observation is especially intriguing: Children who grow up on dairy farms are much less likely than the average child to develop the respiratory disease. Now, a European team studying mice has homed in on a possible explanation: Bits of bacteria found in farm dust trigger an inflammatory response in the animals’ lungs that later protects them from asthma. An enzyme involved in this defense is sometimes disabled in people with asthma, suggesting that treatments inspired by this molecule could ward off the condition in people.

The study, published on page 1106, offers new support for the so-called hygiene hypothesis, a 26-year-old idea that posits that our modern zeal for cleanliness and widespread use of antibiotics have purged the environment of microorganisms that once taught a child’s developing immune system not to overreact to foreign substances.... But others caution that the finding is probably far from the only explanation for why early exposure to microbes can make kids less allergy-prone.

About 20 studies in Europe and elsewhere have found that children raised on farms have relatively low rates of allergies and asthma. Some researchers suspect a key reason is that the kids breathe in air full of molecules from the cell wall of certain bacteria, called lipopolysaccharides for their fat-sugar structure. Also known as endotoxins, these fragments—from dying bacteria in cow manure and fodder—cause a temporary low state of inflammation in the lungs that somehow dampens the immune system’s response to allergens, the thinking goes.

Others who study the hygiene hypothesis caution that the newly uncovered mechanism does not entirely explain the protective effect of dairy farm life. Drinking unprocessed milk also seems to ward off asthma in kids, points out Gary Huffnagle of the University of Michigan, Ann Arbor—and that effect is unlikely to involve the lung epithelium. What’s more, endotoxin levels are not that much higher on farms than in cities, suggesting “it’s too simple an answer,” says asthma genetics researcher William Cookson of Imperial College London, who thinks changes in living microbial communities in the lungs and gut may be just as important.

The key finding in this research (they studied mice, but this process would also happen in humans) is that: the presence of microbes specifically blocks the immune cells responsible for triggering allergies. Once again we see the importance of a healthy and diverse microbiota (the community of microbes within us), and the need to nurture it from birth. Studies have shown the importance of the first year of life in establishing a healthy microbiome and the development of the immune system. A number of studies have shown that the presence of pets or animals (e.g., living on a farm) reduces the incidence of allergies in children.From Science Daily:

Role of microbiota in preventing allergies

The human body is inhabited by billions of symbiotic bacteria, carrying a diversity that is unique to each individual. The microbiota is involved in many mechanisms, including digestion, vitamin synthesis and host defense. It is well established that a loss of bacterial symbionts promotes the development of allergies. Scientists at the Institut Pasteur have succeeded in explaining this phenomenon, and demonstrate how the microbiota acts on the balance of the immune system: the presence of microbes specifically blocks the immune cells responsible for triggering allergies. 

The hygiene hypothesis suggests a link between the decline in infectious diseases and the increase in allergic diseases in industrialized countries. Improvements in hygiene levels necessarily lead to reduced contact with microbes that is paralleled by an increased incidence in allergic and autoimmune diseases, such as type 1 diabetes.

Epidemiological studies have substantiated this hypothesis, by showing that children living in contact with farm animals -- and therefore with more microbial agents -- develop fewer allergies during their lifetime. Conversely, experimental studies have shown that administering antibiotics to mice within the first days of life results in a loss of microbiota, and subsequently, in an increased incidence in allergy.

However, until now, the biological mechanisms underlying this phenomenon remained unclear. In this study published in Science, the team led by Gérard Eberl (head of the Microenvironment and Immunity Unit at the Institut Pasteur) shows that, in mice, symbiotic intestinal microbes act on the immune system by blocking allergic reactions.

Several types of immune response can be generated in order to defend the organism. The presence of bacterial or fungal microbes provokes a response from immune cells known as type 3 cells. These immune cells coordinate the phagocytosis and killing of the microbes. However, in the case of infection by pathogenic agents that are too large to be handled by type 3 cells (such as parasitic worms and certain allergens), the cells that organize the elimination of the pathogen, but also allergic reactions, are known as type 2 cells.

In this study, scientists at the Institut Pasteur have shown that type 3 cells activated during a microbial aggression act directly on type 2 cells and block their activity. Type 2 cells are consequently unable to generate allergic immune responses. This work demonstrates that the microbiota indirectly regulates type 2 immune responses by inducing type 3 cells.

These results explain how an imbalance in microbiota triggers an exaggerated type 2 immune response normally used to fight large parasites, but that also leads to allergic responses....In terms of allergy treatment, a hitherto unexplored therapeutic approach consists therefore in stimulating type 3 cells by mimicking a microbial antigen in order to block allergy-causing type 2 cells.

The researchers were interested in lifestyle factors that are associated with lower rates of allergies.  Prior research has shown that such lifestyle factors are : living on a farm, introducing fish into the child’s diet at an early age, having pets early in life, parental cleaning of the child’s pacifier by sucking it, crowded living conditions, early daycare attendance, and having siblings. This study found that in households washing dishes by hand, rather than in a dishwasher, there are lower rates of allergies and eczema in children. In addition, the study found that consuming fermented or farm-bought food could decrease the likelihood of allergies further. It is thought that early exposure to microbes stimulates the immune system in beneficial ways. Dishwashers leave fewer bacteria behind on dishes than hand washing dishes. Living in a household that hand-washes means family members are eating off of plates and cutlery that have more bacteria, and therefore they are getting more microbial exposure. There could also be more bacteria in the air when dishes are hand washed or even some other lifestyle factor that these households have in common.From NPR:

Kids, Allergies And A Possible Downside To Squeaky Clean Dishes

Could using a dishwashing machine increase the chances your child will develop allergies? That's what some provocative new research suggests — but don't tear out your machine just yet.The study involved 1,029 Swedish children (ages 7 or 8) and found that those whose parents said they mostly wash the family's dishes by hand were significantly less likely to develop eczema, and somewhat less likely to develop allergic asthma and hay fever.

The findings are the latest to support the "hygiene hypothesis," a still-evolving proposition that's been gaining momentum in recent years. The hypothesis basically suggests that people in developed countries are growing up way too clean because of a variety of trends, including the use of hand sanitizers and detergents, and spending too little time around animals.As a result, children don't tend to be exposed to as many bacteria and other microorganisms, and maybe that deprives their immune system of the chance to be trained to recognize microbial friend from foe.That may make the immune system more likely to misfire and overreact in a way that leads to allergies, eczema and asthma, Hesselmar says.

"The hypothesis was that these different dishwashing methods ... are not equally good in reducing bacteria from eating utensils and so on," Hesselmar says. "So we thought that perhaps hand dishwashing was less effective, so that you are exposed to more bacteria" in a way that's helpful.

In a study released Monday in the online version of the journal Pediatrics, the researchers report what they found: In families who said they mostly wash dishes by hand, significantly fewer children had eczema, and somewhat fewer had either asthma or hay fever, compared to kids from families who let machines wash their dishes.

Still, there are other possible explanations, Hesselmar and Mahr both caution. Though the researchers took economic status into account in the study, it could be that people who don't have dishwashers are alike in some other way that reduces their tendency to get allergies. Interestingly, for example, certain other lifestyle characteristics — eating fermented foods regularly, and tending to buy some foods straight from the farm — seemed to strengthen the "protective" effect in families without dishwashers.

This research supports the growing evidence for the importance of microbes in the health of young children. From Science Daily:

Pediatric allergology: Fresh milk keeps infections at bay

A study by researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich shows that infants fed on fresh rather than UHT (ultra-pasteurized) cow's milk are less prone to infection. 

A pan-European study, led by Professor Erika von Mutius, Professor of Pediatric Allergology at LMU and Head of the Asthma and Allergy Department at Dr. von Hauner's Children's Hospital, reports that fresh cow's milk protects young children from respiratory infections, febrile illness and inflammation of the middle earAs untreated cow's milk may itself contain pathogenic microorganisms and could pose a health risk, the researchers argue for the use of processing methods that preserve the protective agents present in raw milk.

The findings are the latest to emerge from the long-term PASTURE study, which is exploring the role of dietary and environmental factors in the development of allergic illness. The study initially recruited 1000 pregnant women who were asked to document their children's diet and state of health at weekly intervals during the first year of life. "Among children who were fed on fresh, unprocessed cow's milk the incidence of head colds and other respiratory infections, febrile and middle-ear inflammation was found to be significantly lower than in the group whose milk ration consisted of the commercially processed ultra-pasteurized product," says Dr. Georg Loss.Ingestion of farm milk reduced the risk of developing these conditions by up to 30%, and the effect was diminished if the milk was heated at home before consumption. Conventionally pasteurized milk retained the ability to reduce the risk of febrile illness, while exposure to the higher temperatures used in UHT processing eliminated the effect altogether. 

"The effects of diverse milk treatments are presumably attributable to differentially heat-resistant components present in fresh milk. Compounds that are sensitive to heating seem to play a particularly important role in protection against respiratory-tract and ear infections," says Loss.

At the end of the first year of life, blood samples were obtained from the children enrolled in the study, and tested for biochemical indicators of immunological function. Infants fed on unprocessed milk were found to have lower levels of the C-reactive protein, which is a measure of inflammation status. "Other studies have shown that higher levels of inflammation are related to the subsequent emergence of chronic conditions such as asthma and obesity. Consumption of unprocessed milk may therefore reduce the risk of developing asthma," Loss explains.

Industrial processing of milk involves short-term heating of the raw product. Conventionally pasteurized milk has been exposed to temperatures of 72-75°C for 15 seconds, while ultra-pasteurized milk undergoes heating at around 135°C for a few seconds. The latter is also homogenized to disperse the milk fats, which prevents the formation of cream. 

In addition to fats and carbohydrates, cow's milk contains proteins that can modulate the function of the immune system. "In many respects, the composition of cow's milk is similar to that of human milk," says Loss. It has long been known that breast-feeding protects infants from infection, although how milk actually affects the early immune function remains unclear. It is possible that some of the factors involved interact directly with viruses or that they promote the development of a healthy immune system by altering the composition of the gut microflora.

That living in the country has positive effects on the immune system has been demonstrated in several previous studies. Together these investigations show, as Erika von Mutius notes, that "children who grow up on traditional dairy farms are least likely to develop allergies.