Seasonal allergies and the microbiome
Seasonal allergies… if you don’t suffer from this, you know someone who does. The sneezing, itchy eyes, asthma triggers. ...Such fun. Other names you might have heard are hay fever and allergic rhinitis. For some it is just an occasional annoyance, but for others, these allergic reactions create a true interruption in life, limiting their options and quality of life.
Explain seasonal allergies to me like I’m a kid…
Seasonal allergy symptoms such as sneezing, coughing, runny nose, itchy eyes, congestion, and more, happen when the body overreacts to normal environmental factors like pollen and mold. Depending on where you live and the time of year, the air you breathe can be extra-full of pollen, dust, mold, and more, and even though it’s natural and not necessarily harmful to humans, the body decides to treat it like a war! The immune system interprets the particles in the air as dangerous invaders when they reach our mucous membranes such as nose, eyes, throat, and lungs.
What does it have to do with our microbiome?
“It is well established that the microbiome can modulate the immune response, from cellular development to organ and tissue formation exerting its effects through multiple interactions with both the innate and acquired branches of the immune system” (Pascal et. al, 2018). To put it plainly, our immune system receives much of its training from our microbiome, specifically our gut-bacteria. The immune system learns what is threatening and what is not, and generally remembers this forever, but it can only learn from what it’s exposed to.
Since allergies and asthma are on the rise, some scientists look to the hygiene-hypothesis as a possible explanation. Introduced in 1989, Dr. David Strachan shared his theory that as our overall cleanliness increases, allergies and asthma have and will continue to increase due to the lack of training opportunities for our immune system that are afforded by environmental/microbial diversity.
If you suffer from seasonal allergies, you are likely to have a less-diverse population of gut bacteria. “American adults with allergies, especially to nuts and seasonal pollen, have low diversity, reduced Clostridiales, and increased Bacteroidales in their gut microbiota. This dysbiosis might be targeted to improve treatment or prevention of allergy.” (Hua, Goeder, Pu, Yu, Shi, 2016)
The condition of our microbiome can affect how we respond to allergens. For example:
In the nasopharynx (where your nose and throat connect), predominance of three specific species (Moraxella, Streptococcus, and Haemophilus) during the first few months of life predicted development of childhood asthma.
Among adolescents in Finland, sensitivity to respiratory allergens was associated with low diversity of Gammaproteobacteria on the skin.
In two studies, infants who had a higher fecal abundance of Clostridium difficile and Escherichia coli, respectively, had an increased risk of developing an allergy in the future.
In a very small Swedish study, low fecal microbial diversity at age 1 month predicted atopic eczema by age 2 years, as well as asthma, by age 7 years. (Hua, Goeder, Pu, Yu, Shi, 2016)
What can I do to help with seasonal allergy symptoms?
Exposure to allergens as a child has been shown to help reduce future allergic reactions, perhaps by training the immune system early on to handle them in an efficient and appropriate way. For example, living on a farm, growing up with a big family, or having cats or dogs as pets has been shown to reduce future allergy struggles! These relate to Dr. Strachan’s hygiene hypothesis.
Many double-blind, placebo-controlled trials have shown that probiotics can be an effective treatment for seasonal allergies. Some specific bacteria that have been studied include Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus casei, Lactobacillus rhamnosus, Bifidobacterium longum, Lactobacillus johnsonii EM1, Lactobacillus gasseri, Bacillus clausii, Escherichia coli Nissle (EcN) 1917. This doesn’t mean that a product with one of these names on the label can cure your annoying allergies. The probiotic market is still generally unregulated and many more studies and specific applications need to be done before recommending a specific probiotic. The general takeaway here is that caring for your microbiome in general, with the information we know for now, is a solid strategy. When we know more, we will adapt! That’s science, baby.
In addition to supporting a diverse microbiome, as discussed earlier, we can take some practical steps to reducing allergy symptoms. When you get home, change your clothes and take a shower- even washing the pollen and such out of your hair. Keep wearing your mask outside, and check your local weather source for pollen levels and air quality status. If your doctor approves, try an occasional sinus rinse, and discuss antihistamines or over-the-counter allergy medications with them or with your pharmacist.
TLDR: Seasonal allergies symptoms result from an overreacting immune response. Overall microbiome diversity, exposure to allergens at a young age, and probiotics can have an effect on allergy symptoms, but this area of study still has a long way to go before we know how to really help.
Sources and helpful info:
Hua, X, Goeder, J. J., Pu, A., Yu, G., Shi, J (2016, January). Allergy associations with the adult fecal microbiota: Analysis of the American Gut Project. EBioMedicine, 3, 172-179. https://www.sciencedirect.com/science/article/pii/S2352396415302218
Pascal, M., Perez-Gordo, M., Caballero, T., Escribese, M. M., Lopez Longo, M. N., Luengo, O., Manso, L., Matheu, V., Seoane, E., Zamorano, M., Labrador, M., & Mayorga, C. (2018). Microbiome and Allergic Diseases. Frontiers in immunology, 9, 1584.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6056614/
Yang, G., Liu, Z. Q., & Yang, P. C. (2013). Treatment of allergic rhinitis with probiotics: an alternative approach. North American journal of medical sciences, 5(8), 465–468.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3784923/
