The mammalian gastrointestinal tract harbors a complex community of microbes — called the gut microbiome — that is essential for the development of the immune system. Despite its complexity, even the presence or absence of some of the many bacterial species that form this community may lead to a variety of disorders of the immune system, especially childhood allergic diseases.
Results from a study published in 2002 show that exposure to 2 or more dogs or cats in the first year of life may reduce the risk of developing allergic disorders during childhood. In 2010, Susan Lynch and her collaborators carried out a study (Man’s best friend? The effect of pet ownership on house dust microbial communities) to understand how the presence of dogs and cats influences the composition of house dust. The researchers found that dust from households with dogs was significantly richer and more diverse compared with that from households without pets, suggesting that the presence of dogs increases the diversity of house dust — as measured by the introduction of additional types of bacteria.
Now, in a new study recently (January 14, 2014) published in the Proceedings of the National Academy of Sciences (House dust exposure mediates gut microbiome Lactobacillus enrichment and airway immune defense against allergens and virus infection), Lynch and collaborators show that, in mice, dog-associated house dust protects against allergies.
The researchers collected dust samples from a home with a dog and, as control, from a home with no pets, and administered the dust to mice. Mice that ingested the dog dust were less likely to develop allergic reactions to cockroach allergen or ovalbumin (a protein found in egg whites) in comparison to mice that ingested dust from homes without pets or mice not exposed to any dust. Indeed, mice that ingested the dog dust exhibited significant changes in their immune response — these changes were consistent with the observed protection from allergies. Their levels of markers associated with allergic disorders and asthma — Th2 cytokines, activated T cells, and immunoglobulin E (IgE) — were greatly reduced in comparison to the other mice.
In addition, mice that ingested the dog dust exhibited a distinct composition of the gut microbiome, which was highly enriched for Lactobacillus johnsonii. Feeding mice live L. johnsonii reduced the allergic responses triggered by cockroach allergen or infection with the respiratory syncytial virus, which are known risk factors for developing childhood asthma. These results indicate that L. johnsonii or other species of “good” bacteria might be used to alter the gut microbiome to prevent the development of asthma or allergic responses.
The researchers now aim to understand the specific role that dust bacteria play in gut colonization and in the composition of the microbiome. Moreover, they aim to identify other factors associated with the dog dust that may alter the composition of the microbiome.
While reading this article the first paragraph jumped out at me. The article states about the microbial community that lives in our gut. Most people believe that all microbes are bad because they make us sick, but that is not true. There are actually more microbes that either help or do no harm to us. The article even states that this community in our gut actually help with our immune system.
After reading the rest of the article, I can see why a dog in the house can help with prevention of future allergies. At a very young age our immune system is only starting to develop, and to introduce a pet in the house can be beneficial. As a baby you are mostly exposed to the house, but the dog can be the messenger to the outside world. Dogs are always going outside and their fur can carry pollen, dust, and various microbes. The dog then comes in contact with the child and the child is now exposed to outside elements, which then allows the immune system to be prepared for future invasions at an early age.
My big question is what’s in a dog’s fur that make it such a help for children’s immune systems? Is it something in their fur, or are they just the carriers? As I have stated above, I think they are just the carriers that are bringing in pathogens from outside, but who knows there could also be something in their fur that help make this microbe community.
I wanted to respond to your statement regarding pet fur. Animal fur is unique in that they have the ability to carry outside microbes as well as their own pet dander. A large population of individuals find themselves allergic to animals not because of the microbes they may have acquired from the outside world, but from their natural skin and fur shedding abilities. So to attempt to answer one of your questions, I believe the developing child’s immune system is strengthened by both the animal’s natural shedding tendencies and the microbes that animals tend to carry.
This is true, M. Brown. I believe that pet fur (dust) does contain many microbes that does play a role in our immune system (I’m sure it also plays a major component of the dogs/cats immune system).
Sara: More specifically, it states in the article that one of the primary bacterium that is present in the dog “dust” is Lactobacillus johnsonii. This bacterium was fed to mice in an experiment. The results showed a reduction in an immune response. I think the next step in this set of experiments is to test whether L. johnsonii also affects the human immune system.
When it comes to allergies, research shows that one of the factors that affects many children is the lack parasitic worms in the Western world. The parasites effect Immunoglobulin E and T-Helper-2 Cells, which becomes activated when an allergic response occurs. I am assuming that L. johnsonii has a similar effect on the immune system.
Amoah AS, Boakye DA, Van Ree R, Yazdanbakhsh M. Parasitic worms and allergies in childhood: insights from population studies 2008–2013. Pediatr Allergy Immunol 2013.
The concept behind having a pet is to introduce a diverse bacterial community to human. This is especially important for babies since their immune systems are still developing and have not exposed much to the environment. The pet, especially the one that constantly moves indoors and outdoors, serve as a middle man to introduce new microbes from air, water, and soil to the babies. Those microbes will prepare the child to develop his/her immune system by making different antibodies for different microbes. Some bacteria from the exposure can help to control the outgrowth of opportunistic bacteria in the air way and GI tract. Because cats tend to stay indoors and are less active than dogs, they bring home a less diverse bacteria community. People nowadays are like cats since we spend most of our time indoors. The bacteria/fungi we encounter everyday mostly come from our household living environment. Not everyone can afford a pet but we can still protect ourselves by being active, by staying close to the nature and exposing to new things. Not only it is fun, it is also beneficial to your health.
The only pet I’ve ever owned was a Cockabird and I always thought that having a dog or cat indoors would expose our family to more bacteria that would most likely harm us. So I was a little surprised with this article, I thought it was unhealthy to have dog-infant interactions since new born immune systems were so weak, and wouldn’t be able to handle dog microbes. Going back to this article, it’s important to note that it does make a difference whether or not the dog is present at the home all day or if the dog spends more time outside and then comes into the home. A study done in 2012 in Finland on the affects of pets on development of children’s respiratory illnesses, observed pets spending less than 6 hours indoors versus pets inside the home at all times. They studied how the exposure to the dust from either scenarios, affects the children’s immunity. It appeared that the dust that the dogs track in, which has much more diverse particles and bacteria from the outdoors, gave stronger benefits to the new borns than dust from pets that stayed indoors. Also, I do wonder if hypoallergenic dogs have the same affect on infant’s immunity or does it matter what kind of dog at all?
Bergroth E, Remes S, Pekkanen J, et al. Respiratory tract illnesses during the first year of life: effect of dog and cat contacts. Pediatrics 2012;130:211–220
This is actually a very interesting question to ask because I have recently read an article that claims that hypoallergenic dogs do not have lower household allergen than other dogs. From what I would think though if they do have lower allergen than it would matter what type of dog it is because hypoallergenic dog are believed to supposedly produce less allergen and shed less than regular animals. They are believed to specifically help those who are already suffering from allergies, to help keep their allergies at a reasonable level of comfort. So if this is true than I believe because they are dogs that carry less allergen they wouldn’t bring as much of a diverse house dust or additional types of bacteria to help children build immunity. Although after reading that article it makes me even question do can a hypoallergenic dog really exist?
It’s important to remember than not all microbes are bad! For example, many of the bacteria found in our gut are beneficial to our health. However, it is important to also realize that in our western-world, we often turn to antibiotics for every little thing, but these kill both the beneficial and harmful bacteria in our systems. I think it’s a really great point to bring up just how much time the dog spends outdoors. This plays a huge role in amount and type of microbes the dog may encounter. But what if we thought about this oppositely? How do we as humans diversify a dog’s immune system?
This article jumped out at me because I have been a pet owner or around pets my entire life. Although there is the saying, “what doesn’t kill you makes you stronger” I was under the impression most people were weary about introducing pets with their infant due to the bacteria possibility. I agree with the post above in relation to exposure. Does the pet need to be indoor all day? How long was the dog even around the mice in the study? I think a time frame could strengthen the results. Are other pathogens noted to have increase in the mice example or just the Lactobacillus? It is interesting to see that being around pets may also cytokine expression. I would be interested to see if the type of animal (cat, dog, ferret, etc) would give similar results or with different pathogens. I think it is a more plausible argument that the animal is a carrier of the pathogen internally, rather than related to fur, but looking at other animals would help. I know this is a recent study, but I would love to see the results with other animals, and see how this progresses.
I actually thought (and so did a few others in the previous comments) that it made more sense for the pathogens to be introduced through the fur of the dog. Dogs like to play outside, run and roll around on the ground, and while doing this, they pick up many different pathogens. And, when the dog comes back inside and rubs up against the baby, or anyone else for that matter, it’s passing on those pathogens. Thus, to answer one of your other questions, it seems to make more sense for the dog to spend a moderate amount of time outdoors to pick up these pathogens, and bring them inside. I believe this would have a more profound effect on the baby’s immune system, than would a dog that stayed at home all day and was not introduced to different pathogens.
Also, you bring up a good point… how long Were the mice exposed to the dog-dust? Duration could have a significant impact on the effectiveness of exposure.
That is a good point. It does make some more sense if the test is looking at dust as well. I was looking at it from the view that a lot of dogs sniff, lick, eat, or somehow ingest many microbes and pathogens, but the article is not about dogs licking the baby directly, so again, the theory of it being in the fur makes more sense to me now.
The name of the article was very interesting to me because I had never heard of anything like a dog helping to protect with childhood allergies. I thought this was a very interesting topic and when I started reading the article the information made sense to me and from what I had learned in my Immunology and Infectious Disease Class. I know that being exposed to diverse microbes helps the person acquire better immunity because they would have already been exposed to the pathogen at least once before and therefore, have better antibodies that are more abundant and specific for that pathogen. We even talked about getting vaccination that would serve as a primary response to things like the flu or chicken pox; so while reading this article I was quit interested in the subject. However, I know some children have allergies with pets like cats and dogs. I personally have allergies to cats and dogs. If cats and dogs can help reduce childhood allergies than what do allergies to the dogs and cats come from?
When someone is allergic to dogs and cats, that means they’re allergic to the proteins found in pet dander, which are flecks of dead skin cells. It’s also possible to be allergic to the proteins found in the animal’s saliva, feces, and urine. These allergens can become airborne, and if inhaled by someone allergic, it can overstimulate the immune system, resulting in your typical allergy symptoms. It’s also possible that you’re not allergic to the pet itself, but to other allergens the animal can carry. For example, dogs and cats tend to collect mold, pollen, and other allergens on their fur, and these may be the reason behind the allergic reaction. This collecting of antigens is also what the previous comments were saying when they were discussing how pets can help introduce children to different pathogens.
One question that came to mind while reading this post and the thought-provoking comments following it was, would the baby not get the least bit sick the first few times it was exposed to the dog harboring these dust pathogens? As stated previously, the baby’s immune system is quite naive, it has not yet been introduced to many common pathogens. So, the first time the baby is introduced to this dog, isn’t it likely to induce a strong immune response because the baby is being exposed to so many new pathogens at once? Thus, I think it would be wise to moderate the exposure to the dog the first few times. For example, maybe the first day the baby is to be exposed to the dog, the dog should be bathed. The following day, maybe the dog should only be allowed for an hour outside and then introduced to the baby. And the next day, a longer period of time outside, and so on. Would this not be a smart thing to do?
I agree with your comment about not exposing young children to many pathogens in the early few months of birth. Like you stated, when children are born, they don’t have any immunity, the only immunity that they have is what is passed from the mother to the child. The mother can pass soluble IgG via her placenta and IgA via breast milk. The only immunity the child has in its early few months is typically due to these two antibodies that have been passed to it by its mother. Exposing the child to too many pathogens in the early ages would not be a smart idea because the baby is already exposed to enough microbes upon birth. Therefore, it’s a good idea to keep pets away from younger babies until they get some acquired immunity.
One excuse people give for not owning pets (other than financial reasons) is that animals trigger allergic reactions. It is definitely interesting to see a study that claims the opposite; exposure to dogs or cats in the first year of life may reduce subsequent risk of allergic reactions during childhood. Furthermore, researchers in Boston, Massachusetts published a study on January 14, 2014 that found a specific bacteria found in dog dust reduced allergic responses in mice.
The study states that mice that ingested the dog dust had significant changes in their immune system. This sparks an interesting question. Can administering babies dog dust produce similar effects to stimulate gut microbiome growth and reduce subsequent allergic disorders? It seems to be a relatively low-risk and low-cost solution for those that cannot afford or do not prefer owning pets. More studies need to be done to examine the role of microbial components of dog dust in reducing allergies for humans before coming to a conclusion.
After examining dog dust for its microbial components, an alternative would be to develop a probiotic that would stimulate beneficial gut microbiome growth. A study has already been done to examine probiotic supplementation in pregnancy and early life. It found that supplementation might help prevent atopic hypersensitivity during growth, but not relieve asthma or wheezing (1).
1) Elazab, N.; Mendy, A.; Gasana, J.; Vieira, E. R.; Quizon, A.; Forno, E. (2013). “Probiotic Administration in Early Life, Atopy, and Asthma: A Meta-analysis of Clinical Trials”. Pediatrics 132 (3): e666–76. doi:10.1542/peds.2013-0246
The article relates to me very well. I never had a pet when I was a kid, but whenever I come over to my best friend’s house who has a dog, I would immediately have a mild allergic reaction. I also remember that I usually have an allergic reaction to basically any new environment that I encountered for the first time, but my friend never have such symptoms. I always wonder why my friend would never have any allergic reaction and I think this article explains the reason why that is so. I feel that the exposure to many microbes at a younger age helps mediate the gut microbiome and reduced allergy reactions because the exposure to the many microorganisms were introduced at an early age. The exposure at a young age allows many microbes (good and bad) to reside in the gut at an early stage, which helps stimulate the immune system. Kids are usually vulnerable, so our immune system works best during this time, in order to protect and prevent infections. It also helps desensitize the immune system from harmless allergens, thus explaining why kids who are more exposed outside or have pets do not usually have allergic reactions. Having a dog around the child, further facilitate the exposure of many microbes because, which only means that the normal flora will be established faster in the child.
This is an interesting article that informs the world that household pets like dogs and cats aid in preventing allergic symptoms. The article explains that dogs help mainly infants with respiratory disorders like respiratory syncytial virus (RSV) and infants that have an increased chance of developing asthma.
I will disagree with the article due to my personal experience. I developed asthma at the age of 2 and still have it now that I am 23 years. Every time that I came into contact with dogs or cats my asthma symptoms develop. The article says that dogs or cats help allergic symptoms then why do I have allergic symptoms when I came into contact with dogs or cats?
I understand where you’re coming from, but it’s important to note that it’s saying children have to be exposed to dogs and cats when they are very young, usually the first year of their lives to be able to develop immunity against allergies. That’s the time it benefits them most since they’re just building up their immunity. In your case, were you exposed to pets before you reached 2 years of age? You would definitely develop allergic reactions to them now because you might not have been introduced to them earlier than 2 years. It just wouldn’t help right now for you to overcome the allergies when you’re in contact with these pets, it can only happen very early in life. Of course there are other factors that might have cause your asthma and allergies, genetic and even environmental.
The reason I disagree is that they need to perform more experiments before conforming that dogs and cats help in preventing allergies. I was exposed to dogs at the age of one but they did not assist in preventing me from getting asthma when I become two years old.
Many scientists have discovered a link between helminths and the lack of allergies in humans. This claim explains how exposure to parasitic organisms is capable of reducing an immune response to allergins. Some speculate that a mutual symbiotic relationship occurs between the parasite and the human. While the parasite is able to survive inside of a host, the parasite induces an immune response preventing many allergins. In fact, some scientists are wondering how long it will take the medical world to adopt the use of helminths to reduce allergies.
Figueiredo CA, Cooper P, Barreto M, Alcântara-Neves NM, Barnes K. “Conference scene: Parasites to treat immune-mediated diseases?”. Future Medicine. Vol. 4, No. 6, (2012) Pages 573-575 . PubMed. Web. 2/13/2014
In reading this article I found the method of using dogs to aid in preventing allergy very intriguing because not only are dogs are being use to help children with their immune system but they are also being use to help in detecting cancer in adults. Researchers have found that dogs have an ability to ‘smell in color” and are being use more and more to aid in finding cancer that generally cannot be found until its grown to a size that can be diagnosed. So in reading that dogs are also useful in helping to build immunity is really amazing to hear and makes me question what is it about them that makes them so unique to do this such things?
In reading another article about breast milk and maternal antibodies I also realize how the composition of the gut mircobiome truly plays an important factor in our immune system and health. In an article written by Roberta Attanasio, one of things she talks about is the importance of breast milk and how it secretes Iga, which is an antibody that helps babies to obtain a healthy gut microbiota. The article also talks about how research was done in rats to see the difference between those who had Iga and those who didn’t and found that those who didn’t were more at risk to get an intestinal inflammatory disease. They were also found to have a different composition of the gut mircobiome. So in reading this article and how “good” bacteria are being used to alter the gut mircobiome to help prevent asthma, I realize how it lines up with the breast feeding article and showing how changing the gut composition can truly make an impact on a person health. It seems to me that the gut mircobiome have so much interesting factors to it that should be study more. I even read in another article how it might even be connect to obesity and weight loss. It makes me even question if in changing the gut mircobiome could it also help in cure diseases too?
This article provides a bold statement, especially when the CDC states that food allergies have increased 50% between 1971 and 2011. 50%?! That number is astronomical. We all hear it on the news every day about more and more children developing not just a single allergy, but numerous allergies. Allergies are simply very specific, reproducible immune system responses that are typically unwanted and unpleasant. The UCLA Food and Allergy Care Center suggests the reasoning behind allergies is the “Hygiene Hypothesis,” (http://fooddrugallergy.ucla.edu/body.cfm?id=40). Basically, it claims an increase in allergic occurrences is due to over-cleanliness. Some ideas they ask you to consider include having siblings, putting children in daycare centers, and simply spending time outdoors. All three of these events in the early years of childhood provide exposure, and through exposure protection, because naive/resting lymphocytes can mature through recognition and activate the proliferation on antibodies. Therefore, in future exposures, the lag phase of recognition may be surpassed, and clonal selection may be started right away. It’s almost like having a little army of antibodies waiting on the sidelines that will recognize every little microbe we encounter. Kind of cool, right? And dogs are just another example of this. They bring more than joy and happiness to our lives, but an abundance of microbes that make our world diverse in more ways than one! However, in our modern world, there are many people that refuse to have dogs as pets, they have only one child, and that nurture that child at home and possible even homeschool that child, and just to top it off, they’re probably germ-a-phobes and clean every inch the child will ever touch. This scenario is just asking for a slew of allergies and complications later in life. There comes a point where attempting to protect has gone too far, and people need to become aware of this. So, have a dog, play in some dirt, hey even play in some dirt WITH a dog! In the end, you’ll have a good time and will be doing yourself a favor without even knowing it.
I also wanted to add on how the microbiome gut seem to play a huge role in our immune system and how we do not seem to hear much about it. It seems that scientist our recognizing it more and more how much of an impact it has on our immune system when its composition changes. Now my question is would the microbiome be part of the innate immune system, adaptive immune system, both, neither, or is it its own thing?
The microbiome in human systems that benefit humans is not part of the immune system. The micobiomes that live in our gut live in a symbiotic relationship with us, where we, humans, mostly benefit. If we killed these microbiomes that would be detrimental to our health, so these microbiomes have created a system. The flora in our gut establish a “cross-talk” with our immune system, so the immune system does not attack these microorganisms that benefit and are needed for our system. When the immune system starts to attack our natural flora, an autoimmune disease can occur. This can conclude that our natural flora is not part of the immune system because we have millions of bacteria that make up our gut flora.
Thanks for the information! As a matter of fact I found it fascinating how they mention in the article,how it is important for the flora in our gut to maintain that ” cross-talk” with our immune system or auto-inflammatory disease may occur because in another article by Roberta Attanasio, one of the major points she talks about is the importance secretory IgA in breast milk. She explains how researchers have done a study where they had found that IgA can help in protecting against harmful microbes and how they found that the mice they use that lack IgA, had a different gut microbioma that exhibited altered genes, which in humans is associated with intestinal inflammatory disease. It’s cool to see how all this kind of connects.
In reading several of the comments by other individuals, I’ve noticed a focus on the concept of developing an immune response to allergins, when exposed to dogs and cats at a young age. Why is it that adults don’t develop this immune response later on in life? In other words, if the immune system of children is capable of adapting to produce an immune response, why does the immune response of adults incapable of also adapting to an allergic response? Maybe it’s because at a certain age in childhood, the parts of the immune system, such as IgE, stop evolving and adapting to its surroundings. Also, what is this cut-off age in which a human will no longer produce an effective response to allergins, and will instead begin to develop the dreaded allergic reactions that many of us suffer throughout our lives?
Reading both the article and several of the responses it is clear that immunity is greatly influenced at a young age. Though like many have stated before I think moderately exposing a child is the best way to generate a healthy immune response, how much is just enough versus “too much”. I have a friend that is highly allergic to dogs and cats but does this mean that if he was exposed to them at a younger age that he would have reduced the severity or simply developed this allergy at all? From this article the bacteria harbored in the gut that helps to prevent allergic reactions is Lactobacillus johnsonii. As many companies have already started developing and advertising the advantages of probiotics, could incorporating this particular bacteria into formulas or as a infant supplement be an option for the future? As the hair from dog causes increased production of this bacteria in the gut, what about the families that can’t have pets? Are their children doomed with a life full of allergic reactions? I am especially interested in seeing A) if this particular allergen blocking bacteria could be synthetically introduced and B) if exposure to animals (particularly dogs) could reduce the chances of a child being allergic to them at an older age.