Understanding Your Child’s Immune System
Understand the role that vaccines, allergies, and more play in your child’s immune health
Learn more about how immunizations work and why vaccines are one of the most important advances in the history of medicine.
Understanding the Immune Response
A typical immune response begins with your innate immune system. Cells of the innate immune system are “first responders” rapidly sensing molecular features common to many infectious pathogens and/or the damage they inflict. If these features are detected, the innate immune system responds by making inflammatory molecules. This inflammation usually slows the pathogen down and kickstarts cells of the adaptive immune system, which produces antibodies and T cells that are tailored to the pathogen. Once the infection is cleared, the adaptive immune system leaves behind some of its best cells that ‘remember’ the pathogen. This is called immunological memory, and it allows you to clear the infectious pathogen much more quickly the next time you are exposed.
How are vaccines tested and approved?
In addition to knowing how vaccines work, understanding the process of vaccine testing can help alleviate any concerns you might have for your family about immunization and vaccine safety.
Are vaccines safe for children?
Yes, and learning the truth about some common vaccine myths can help you feel even more confident in their safety for your family.
Pediatric immunizations: Separating the facts from fiction with vaccine safety
Vaccines are among the safest, most successful, and most reliable medical interventions, saving countless lives over the years. In fact, childhood vaccination alone prevents 4 million deaths each year. Decades of research show that—when weighed against the risks of actual infection—the benefits of vaccines far outweigh their very small risks. Vaccines have been crucial in preventing and even eradicating many infectious diseases. During disease outbreaks like the COVID-19 pandemic, vaccines have been essential in reducing the disease’s impact on public health. Despite this, misinformation has led some people to question vaccine safety.
Some claims about vaccine risks are false. For instance, the idea that the childhood vaccine against measles, mumps, and rubella (MMR) causes autism is based on a discredited study wrongly linking the MMR vaccine to autism in a small group of children. When it was discovered that the lead scientist manipulated and falsified the data, the findings from this study were retracted. Many studies1,2,3 by other groups found no link between the MMR vaccine and autism. Similarly, the small amounts of Thimerosal, a vaccine preservative that included small amount of mercury, also has no relationship to autism. Rates of autism have continued to rise despite the fact that Thimerosol ceased to be used as a preservative in childhood vaccines decades ago.12
Don’t let these myths or others stop you from safely protecting your child against infectious diseases. If you have any concerns about vaccinations for children, talk to your pediatrician. For more information, visit the CDC’s page on vaccine basics and common questions.
Things to remember…
Recommendations evolve over time: As new scientific evidence and research emerge, doctors refine and optimize vaccination recommendations to provide the best protection against diseases based on the most current information.
Talk to trusted sources for up-to-date recommendations: Find the latest vaccine recommendations for your child’s health needs by talking with trusted sources, like your child’s doctor, who can provide personalized guidance based on their medical history and current guidelines.
Stay informed: Official health agency websites can provide accurate and current information on recommended vaccines for children, ensuring you have access to reliable sources to make informed decisions about your child’s vaccinations. (See a list of recommended websites in the Resources section below.)
Why does my child get seasonal allergies?
The immune system learns to recognize the proteins and molecules produced naturally by the body from those produced by foreign invaders like bacteria and viruses. When it detects the invaders, it activates and responds to clear them out, guided by inflammatory molecules triggered by the infection.
The immune system also ignores harmless materials, like pollen, that don’t usually cause inflammation. But in some people, the immune system can mistakenly attack pollen, treating it like a harmful invader.
Through research, scientists have found key molecules and cells involved in allergies. They’ve identified a specific antibody called immunoglobulin E (IgE) and certain immune cells, like mast cells, that produce inflammatory molecules such as histamine4 and leukotrienes.5 These molecules cause allergic symptoms like sneezing, coughing, and a runny nose.
Why does my child have food allergies?
As with seasonal allergies, food allergies happen when the immune system reacts to certain foods, like peanuts, as if they’re invaders. These reactions can be serious.
Scientists aren’t certain why some children develop food allergies. One reason could be that some young children aren’t exposed to certain foods while their immune systems are still growing and developing. For example, research suggests that early introduction of peanuts could lower the risk of peanut allergies in children.9 This was highlighted in a recent study called Learning Early About Peanuts (LEAP), which found that children who eat peanuts at a young age are less likely to develop a peanut allergy.
It’s like how your body reacts differently if someone comes into your house through the front door versus sneaking in through a window. If peanuts are “invited” in through the mouth, your immune system learns to tolerate them. But if your first encounter with peanut protein is through the skin, for example through skin products with peanut oil (which may be contaminated with peanut proteins) your immune system sees them as intruders and can develop an allergy. For children with uncontrolled atopic dermatitis (also known as eczema), whose skin barrier is disrupted, the chances of developing allergic immune responses to food proteins through the skin is higher than the general population. It’s important to keep in mind that this has not been studied for all allergens (just the peanut so far), and that it is important to partner with your child’s pediatrician before you give your child potentially allergenic foods like a peanut, particularly if there is a higher risk of allergies in your family.
In addition, there is a growing understanding that microbes that live on us and in us in harmony (also known as commensal microbes) interact with our immune system to promote tolerance to food. Immunologists are actively studying whether shifts in these commensal microbes, especially in our gut, may contribute to the development of food allergies and other allergic diseases.
How has understanding the immune system advanced treatments for food and seasonal allergies?
Scientists are using what they know about allergic reactions to create new treatments for both food allergies and seasonal allergies. For example, from basic research, scientists learned how certain substances contribute to seasonal allergies and have used this knowledge to develop drugs6 that help control allergy symptoms by blocking histamine or leukotrienes.7 Some allergy sufferers can also benefit from immunotherapy,8 like allergy shots, drops or tablets, where the immune system is exposed to small amounts of allergens over time to help modify the body’s allergic response.
For food allergies, research on how eating small amounts of allergenic foods can change how the immune system reacts led to the FDA approving the first oral therapy for peanut allergies in 2020. With this treatment, people gradually eat more peanuts to make their immune system less sensitive to them, reducing allergic reactions. Another treatment recently approved by the FDA blocks IgE, a specific type of antibody involved in allergies, lowering the risk of severe reactions if someone accidentally eats a food they’re allergic to.10,11 While avoiding allergenic foods is still important, these therapies offer extra protection. The use of allergy drops under the tongue is also under active investigation to treat food allergy and is used in some allergy practices to treat food allergy. Unlike with seasonal allergies, there are currently no allergy shots approved to treat food allergies.
If you want to learn more, talk to your healthcare provider.
Looking for more information? Visit these trusted resources to learn more about supporting your child’s health:
Sources
- Jain, A., Marshall, J., Buikema, A., Bancroft, T., Kelly, J. P., & Newschaffer, C. J. (2015). Autism Occurrence by MMR Vaccine Status Among US Children With Older Siblings With and Without Autism. JAMA, 313(15), 1534. https://doi.org/10.1001/jama.2015.3077
- Taylor, B., Miller, E., Farrington, Cp., Petropoulos, M.-C., Favot-Mayaud, I., Li, J., & Waight, P. A. (1999). Autism and measles, mumps, and rubella vaccine: no epidemiological evidence for a causal association. The Lancet, 353(9169), 2026–2029. https://doi.org/10.1016/s0140-6736(99)01239-8
- Madsen, K. M., Hviid, A., Vestergaard, M., Schendel, D., Wohlfahrt, J., Thorsen, P., Olsen, J., & Melbye, M. (2002). A Population-Based Study of Measles, Mumps, and Rubella Vaccination and Autism. New England Journal of Medicine, 347(19), 1477–1482. https://doi.org/10.1056/nejmoa021134
- Dale HH, Laidlaw PP. The physiological action of beta-iminazolylethylamine. J Physiol. 1910 Dec 31;41(5):318-44. doi: 10.1113/jphysiol.1910.sp001406. PMID: 16993030; PMCID: PMC1512903. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1512903/
- Peters-Golden, M., Gleason, M. M., & Togias, A. (2006). Cysteinyl leukotrienes: multi-functional mediators in allergic rhinitis. Allergy, 61(6), 658-668. https://doi.org/10.1111/j.1365-2222.2006.02498.x
- Hore, I., Georgalas, C., & G. Scadding. (2005). Oral antihistamines for the symptom of nasal obstruction in persistent allergic rhinitis – a systematic review of randomized controlled trials. Clinical & Experimental Allergy/Clinical and Experimental Allergy, 35(2), 207–212. https://doi.org/10.1111/j.1365-2222.2005.02159.x
- Donnelly A.L., Glass M., Minkwitz M.C., Casale T.B. (1995) The leukotriene D4-receptor antagonist, ICI 204,219, relieves symptoms of acute seasonal allergic rhinitis. American Journal of Respiratory and Critical Care Medicine. 151(6):1734-9. https://www.atsjournals.org/doi/10.1164/ajrccm.151.6.7767514
- Penagos, M., & Durham, S. R. (2022). Allergen immunotherapy for long-term tolerance and prevention. 149(3), 802–811. https://doi.org/10.1016/j.jaci.2022.01.007
- Du Toit, G., Roberts, G., Sayre, P. H., Bahnson, H. T., Radulovic, S., Santos, A. F., Brough, H. A., Phippard, D., Basting, M., Feeney, M., Turcanu, V., Sever, M. L., Gomez Lorenzo, M., Plaut, M., & Lack, G. (2015). Randomized trial of peanut consumption in infants at risk for peanut allergy. The New England Journal of Medicine, 372(9), 803–813. https://doi.org/10.1056/NEJMoa1414850
- Wood, R. A., Alkis Togias, Sicherer, S. H., Shreffler, W. G., Kim, E. H., Jones, S. M., Donald Y.M. Leung, Vickery, B. P., J. Andrew Bird, Spergel, J. M., Iqbal, A., Olsson, J., Ligueros-Saylan, M., Uddin, A., Calatroni, A., Charmaine Marquis Huckabee, Rogers, N. H., Yovetich, N., Dantzer, J., & Mudd, K. (2024). Omalizumab for the Treatment of Multiple Food Allergies. The New England Journal of Medicine. https://doi.org/10.1056/nejmoa2312382
- Commissioner, O. of the. (2024, February 16). FDA Approves First Medication to Help Reduce Allergic Reactions to Multiple Foods After Accidental Exposure. FDA. https://www.fda.gov/news-events/press-announcements/fda-approves-first-medication-help-reduce-allergic-reactions-multiple-foods-after-accidental
- https://www.cdc.gov/vaccinesafety/concerns/thimerosal/index.html