How to Boost Your Child’s Immune System

Every parent has been there: it’s the third cold this month, the school year has barely started, and you’re wondering if there’s anything you can actually do to help your child get sick less often. The good news is that a child’s immune system develops over time, and everyday habits can genuinely help it work better. Below is a look at what peer-reviewed research says, with a special focus on a well-studied trio of probiotic strains and why chewable formats tend to work better for kids in real life.

Why Kids Get Sick So Often (and Why That’s Normal)

Young children average many more respiratory infections per year than adults simply because their immune systems are still “learning” as they encounter new viruses and bacteria for the very first time. This is especially true once they’re in daycare or school with other kids. This is a normal part of development, not a sign that something is wrong. That said, several everyday factors—gut health, sleep, physical activity, and nutrition—have real, measurable effects on how well a child’s immune system responds to those everyday exposures.

Probiotics: Supporting Immunity Through the Gut

Roughly 70-80 percent of the immune system’s activity originates in the gut, where trillions of bacteria constantly interact with immune cells lining the intestinal wall.¹ This is why researchers have spent the last two decades studying whether adding specific “good” bacteria in the form of probiotics can help train and support that immune response.

Three strains in particular have been studied together in clinical research: Lactobacillus gasseri, Bifidobacterium bifidum, and Bifidobacterium longum.

A randomized, double-blind, placebo-controlled trial involving a group of adults tested a combination of Lactobacillus gasseri KS-13, Bifidobacterium longum G9-1, and Bifidobacterium bifidum MM-2 or a placebo twice daily for three weeks. At the end of the study, the researchers found that those taking the probiotics maintained special T-helper white blood cells called CD4+ lymphocytes. CD4+ stimulates other immune cells (B cells) to protect against pathogens by making proteins called antibodies.²

Although this trial focused on adults, it’s important for understanding how this specific probiotic combination behaves in the body. It also lays a foundation for other research showing how these probiotic strains help keep children healthy. For example, a systematic review in Expert Opinion on Biological Therapy looked specifically at Lactobacillus and Bifidobacterium strains in healthy children, pooling the results from 14 randomized controlled trials. The review concluded that probiotics in healthy children reduced how often upper respiratory infections occurred and how severe symptoms were when they did happen. The researchers noted that even a five to ten percent reduction in infections could have a meaningful impact for families and communities. Importantly, long-term probiotic use also appeared to have a good safety profile in children, with no serious adverse events reported across the studies reviewed.³

More recent research on B. longum specifically adds to this picture. A 2025 randomized trial gave B. longum to 50 children over three months and compared them to 50 children given a placebo. The children who received the probiotic had significantly fewer upper respiratory tract infections than the placebo group, and the supplement was shown to increase levels of protective antibodies in the gut while reducing inflammatory markers.⁴

The takeaway? Research on Lactobacillus and Bifidobacterium strains as a category, including the three strains discussed here, points toward a real benefit for reducing how often kids catch colds and how severe those colds are.

Why Chewable Tablets Matter

Even the best-studied probiotic strain does nothing if a child won’t take it consistently—and taste and texture are consistently the biggest barriers to that. A 2020 study on chewable pediatric medications found that a lack of palatability is a major obstacle to compliance in children—and both parents and pediatricians recognize that taste is one of the most common reasons kids refuse to take a supplement or medication in the first place. What’s more, chewable formulations offer real practical advantages over liquids and hard capsules, including more precise dosing, better stability, and easier storage.

This matters because consistency is everything with probiotics—a strain only has a chance to support gut health if it’s taken regularly over weeks or months. This same study also found that 97 percent of children adhered to a full dose of a chewable formulation, and the large majority of children said they’d be willing to take it again in the future. ⁵

4 Lifestyle Habits That Support Immune Health

Probiotics work best as part of a broader picture. The following everyday habits have solid research behind them too.

1. Prioritize Sleep

Sleep and the immune system are deeply connected. A 2015 review in the Journal of Immunology Research explains that a lack of sleep can weaken immunity and increase the susceptibility to infection.⁶ While that study didn’t focus specifically on children, a more recent analysis of preschoolers from the EDEN birth cohort found that young kids with a pattern of persistently short sleep (less than 10 hours a night) had measurably higher levels of an inflammatory marker (IL-6) in their blood at age five.⁷ Prioritizing a consistent, age-appropriate amount of sleep can play a key role in how well a child’s immune system is regulated.

2. Keep Kids Physically Active

Movement matters as well. A study published in Pediatric Research looked at the relationship between physical activity and respiratory infections in preschool-aged children and found a link between lower amounts of physical activity and a higher frequency of respiratory tract infections in preschoolers. On the flip side, getting plenty of active play on repeat appears to be genuinely protective for children’s respiratory health.⁸

3. Build Meals Around Fruits, Vegetables, and Key Nutrients

What your child eats on a daily basis plays a critical role in how well their immune system functions. One review published by researchers at Johns Hopkins clearly shows how vitamin A, vitamin D, iron, zinc, and selenium help regulate a child’s immune response against pathogens and protect against oxidative stress and inflammation.⁹

A diet filled with minimally-processed fruits and vegetables can help kids get a daily dose of these immune-supporting nutrients. A randomized controlled trial in children with asthma tested whether increasing fruit and vegetable intake changed immune outcomes. Children assigned to a high fruit-and-vegetable diet for six months had significantly fewer asthma attacks than children on their usual, lower-intake diet.¹⁰ While this particular study focused on kids with asthma, it adds to a broader pattern: diets richer in fruits and vegetables are repeatedly linked to better respiratory and immune outcomes in kids.

4. Don’t Overlook the Basics

Handwashing, routine vaccinations, and simply trying to limit close contact when siblings or classmates are sick remain some of the most effective tools for keeping kids healthy.^11,12 Just remember, none of the strategies above, probiotics included, are meant to replace these fundamentals.

Putting It All Together

No single strategy will make a child immune to every cold that goes around a classroom. But the evidence does support a few concrete, low-risk habits: a daily probiotic featuring well-studied strains like Lactobacillus gasseri KS-13, Bifidobacterium bifidum G9-1, and Bifidobacterium longum MM-2 (in a chewable tablet form your child will actually take consistently), reliable sleep, regular active play, and a diet built around fruits and vegetables. Together, these habits give a child’s developing immune system real, evidence-based support.

References

1. Wiertsema SP, van Bergenhenegouwen J, Garssen J, et al. The interplay between the gut microbiome and the immune system in the context of infectious diseases throughout life and the role of nutrition in optimizing treatment strategies. Nutrients. 2021;13(3):886.
2. Spaiser SJ, Culpepper T, Nieves C Jr, et al. Lactobacillus gasseri KS-13, Bifidobacterium bifidum G9-1, and Bifidobacterium longum MM-2 ingestion induces a less inflammatory cytokine profile and a potentially beneficial shift in gut microbiota in older adults: a randomized, double-blind, placebo-controlled, crossover study. Journal of the American College of Nutrition. 2015;34(6):459-69.
3. Ozen M, Kocabas Sandal G, Dinleyici EC. Probiotics for the prevention of pediatric upper respiratory tract infections: a systematic review. Expert Opinion in Biological Therapy. 2015;15(1):9-20.
4. Zhang X, Chen K, Lan H, et al. Effect ofBifidobacterium longum  infantis YLGB-1496 on common diseases in pediatrics: a randomized, blinded, placebo-controlled trial. Frontiers in Nutrition. 2025;12:1585504.
5. Barnett S, Bhatt A. A chewable pediatric preparation of ibuprofen is palatable and acceptable to children. Paediatric and Neonatal Pain. 2020;2(1):2-6.
6. Ibarra-Coronado EG, Pantaleón-Martínez AM, Velazquéz-Moctezuma J, et al. The bidirectional relationship between sleep and immunity against infections. Journal of Immunology Research. 2015;2015:678164.
7. Radmanish M, Khalfallah O, Glaichenhaus N, et al. Sleep duration trajectories associated with levels of specific serum cytokines at age 5: A longitudinal study in preschoolers from the EDEN birth cohort. Brain Behavior & Immunity-Health. 2022;21:100429.
8. Ostrzyżek-Przeździecka K, Panczyk M, Bronikowski M, et AL. Association of low physical activity with higher respiratory tract infections frequency among pre-school children. Pediatric Research. 2023;94(2):594-602.
9. Palmer AC, Bedsaul-Fryer JR, Stephennseb CB. Interactions of nutrition and infection: the role of micronutrient deficiencies in the immune response to pathogens and implications for child health. Annual Review of Nutrition. 2024;44(1):99-124.
10. Hosseini B, Berthon BS, Jensen ME, et al. The effects of increasing fruit and vegetable intake in children with asthma on the modulation of innate immune responses. Nutrients. 2022;14(15):3087.
11. Xun Y, Shi Q, Yang N, et al. Associations of hand washing frequency with the incidence of illness: a systematic review and meta-analysis. Annals of Translational Medicine. 2021;9(5):395.
12. Talbird SE, Carrico J, La EM, et al. Impact of routine childhood immunization in reducing vaccine-preventable diseases in the United States. 2022;150(3):e2021056013.

This article is for informational purposes only. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice.