The guy in the middle seat coughs and sneezes as you shiver in the icy airplane cabin. Just an allergy he reassures, you won’t catch it.

Still, whether it's an allergy or summer cold, the body’s hard-working respiratory system gets no vacation.

Our microbes figure prominently in shoring up respiratory health, not least by their impact on immunity and inflammation. When faced with an intruder—whether an allergen like summer pollen or an infection from a hacking seatmate—our body does one of two things: fights or tolerates it. Research has shown that crosstalk between gut microbes and innate and adaptive immune response mediates what happens.

All too often though our microbes aren’t up to the task.  Two reasons:

• Dysbiosis in the gut. Unhealthy diets lacking in fiber or fermented foods, strong medications, and a sedentary lifestyle can all lead to this common condition where microbes fail the test.
• Lack of exposure before the threat is severe. Modern life shields us from bacteria and foreign agents and therefore lowers defenses when needed. This hygiene theory advocates for less use of anti-bacterials.

Probiotics and respiration

The chatter between microbes and immunity is bolstered by good bacteria. Probiotics, whether through fermented foods or supplements, have a beneficial role in respiration affronts including colds and allergies.

A body of research has defined the pathways.

• Immune system strengthened to fight infections as reported earlier
• Intestinal permeability for pathogen passage is reduced
• Inflammation reduced

Probiotic benefits in colds

As most parents know, daycare is an incubator for cold infections, presumably because of new exposure.  One small study done in Europe combined probiotics and vitamin C to see if respiratory illness could be prevented.

Fifty-seven preschoolers received probiotics (Lactobacillus and Bifidobacterium) plus 50 mg vitamin C or a placebo daily for 6 months.  The probiotic mixture when compared to placebo reduced upper respiratory tract infection (URTI), number of days with URTI and absence from preschool.

Another experiment tested fermented milk supplemented with Lactobacillus rhamnosus strains with hospital patients. Respiratory tract infections were fewer as well as briefer.

And with a bit more heft to the results, a meta-analysis analyzed 20 randomized controlled trials to see if probiotics impacted duration of respiratory illness in healthy adults and children. The authors concluded that Lactobacillus and Bifidobacterium strains reduced the average duration of illness episodes, the number of days of illness per person and the number of days absent from work or school or day care as opposed to those people treated with placebo.

The microbe-allergy link

Allergies are different obviously in that the pathogen is not an infection. Allergic rhinitis is most akin to a cold; it is caused by an inflammatory reaction. Relief comes with various medications: Antihistamines, bronchodilators, and corticosteroids.  These fixes like most drugs can cause side effects.

What if probiotics—with minimal downsides—could intervene?

Probiotics do exert anti-inflammatory and immune-modulatory activity, maybe sufficient enough to manage allergies.

Probiotics may modulate allergic response by stimulating Th1 pathways and restoring Tregs, both which help control acquired immunity. In addition, probiotics may promote the production of some cytokines, including IL-10, TGF-β, IL-12, and IFN-γ, which regulate the immune response and dampen allergic inflammation.

Bearing that out, in past studies, probiotic supplementation with both Lactobacilli and Bifidobacteria showed positive outcomes.

One 2017 study conducted at the Second University of Naples asked whether a mixture of three Bifidobacteria species would impact nasal symptoms and quality of life (QoL) in children.

Forty children with a mean age of 9 were treated to probiotic or placebo for 4 weeks. Results showed that the children treated with probiotic mixture realized an improvement of symptoms (nasal itching, sneezing, rhinorrhea, nasal obstruction, and itchy eyes) and QoL yet the placebo group actually had worsening of symptoms and QoL.

Fewer questions were asked in one recent clinical trial; the mini Rhinoconjunctivitis Quality of Life (mRQLQ) questionnaire revealed that 25 of 40 participants responded well after 8 weeks of consuming a probiotic supplement twice daily.  Symptoms subsided enough for some to cut down on allergy medications in the final four weeks.

And in further backing from a body of evidence, a 2015 meta-analysis found a role for probiotics in the management of allergic rhinitis.

Take-away

Try to avoid those summer colds and allergies by eating more fermented foods including yogurt, kimchi and kefir. Include lots of fruits and vegetables from the summer harvest to keep those good microbes colonizing.

A supplement for good measure is also suggested. But importantly, know that each strain acts differently. The mechanisms described are bacterial strain or metabolite specific and should not be extrapolated to other probiotics or prebiotics.

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Author Clare Fleishman MS RD bridges the gap between science and health across most platforms: major newspapers, magazines, books, workshops, social media and websites. In 2010, she launched www.ProbioticsNow.com to share the cascade of new discovery in the microbiome. Always amazed at this “forgotten organ,” Fleishman also creates white papers, blogs, videos and social media for the International Probiotics Association.

The International Probiotics Association (IPA) is a global non-profit organization bringing together through its membership, the probiotic sector’s stakeholders including but not limited to academia, scientists, health care professionals, consumers, industry and regulators. The IPA’s mission is to promote the safe and efficacious use of probiotics throughout the world. Holding NGO status before Codex Alimentarius, the IPA is also recognized as the unified “Global Voice of Probiotics®” around the world.