September is a month of new shoes, new teachers, new routines and, for many families, a familiar cycle of coughs, colds and stomach bugs. Children suddenly move from the relatively small social circles of the summer holidays into classrooms, corridors, lunch halls and playgrounds full of other children. That means a lot more opportunities for viruses and other infections to spread.
The numbers show just how predictable the autumn rise can be. Department for Education data for England found that overall school absence rose from 4.75% in the first week of the 2025/26 autumn term to 8.91% in the final week before Christmas. Much of the later increase was driven by illness. This is not simply a parenting impression: sickness really does rise as the term progresses.
The NHS says children have around five to eight colds a year on average. Young children are still building immunity to the hundreds of viruses that can cause a cold, so repeated infections are a normal part of childhood. But that does not mean there is nothing we can do. We cannot create an impenetrable immune system, and nor would we want to. What we can do is give a developing immune system the conditions it needs to work well.
Increasingly, that conversation leads us somewhere fascinating: the gut.
Why do some children seem to catch everything?
Put thirty children into the same classroom and their exposure may look similar, but their experience of the school term can be very different. One child seems to pick up every cold going. Another catches very little. There is no single explanation. Age, previous exposure, vaccination, underlying health, sleep, stress, nutrition, genetics and chance can all play a part.
The immune system is also not a single switch that is either 'strong' or 'weak'. It is a highly coordinated network of cells, tissues, barriers and chemical signals. A healthy immune response needs to recognise genuine threats, respond appropriately and then settle down again.
One of the places where that immune education happens is the gut. The intestinal lining is in constant contact with food, microbes and microbial metabolites, so the gut microbiome and immune system are in continual conversation. Research increasingly describes early life and childhood as important periods for the development of the microbiome, epithelial barriers and immune function.
The gut and immune system: what is the connection?
You may have seen claims that '70% or 80% of the immune system is in the gut'. This is a memorable statement, but it is also an oversimplification, so we would rather explain what we actually know.
The gut contains a very large collection of immune cells and immune tissue. It is also home to trillions of microorganisms and an enormous surface that separates the outside world from the inside of the body. The microbes living there can interact with immune cells directly and, importantly, through the substances they produce when they metabolise our food.
Dietary fibre is a good example. Certain gut microbes ferment fibres that we cannot digest ourselves, producing short-chain fatty acids such as acetate, propionate and butyrate. These compounds are involved in maintaining the intestinal barrier and in signalling pathways that help regulate immune activity. Reviews in both paediatric nutrition and immunology increasingly point to this diet–microbiome–immune relationship.
This is one reason we think supporting a child's microbiome makes more sense than talking about simply 'boosting' immunity. Immune health is about balance, resilience and appropriate responses, not turning the immune system up as high as possible.
1. Start with diversity on the plate
Variety is one of the simplest places to start. Rather than becoming fixated on a single 'superfood', aim to expose children to a broad range of plant foods across the week: vegetables, fruit, beans, lentils, whole grains, nuts and seeds where age-appropriate and safe.
Different plants contain different fibres and plant compounds, which in turn provide substrates for different members of the gut microbial community. Research in children supports the importance of dietary fibre for the microbiome, gastrointestinal barrier and wider immune and metabolic pathways.
For a lunchbox, this does not have to mean anything elaborate. Think in colours and textures: berries one day, apple the next; carrot sticks, cucumber, peas or sweetcorn; oatcakes or wholegrain bread; hummus or another pulse-based dip. The goal is not dietary perfection but a repeated exposure to variety.
This matters particularly because many children do not eat enough fibre. A 2026 review of paediatric gastrointestinal health concluded that inadequate fibre intake remains widespread, while fibre plays an important role in microbiota composition, gut barrier function and immune and metabolic signalling.
2. Know the difference between prebiotics, probiotics and fermented foods
These words are often bundled together, but they are not interchangeable.
Prebiotics are substrates that are selectively used by microorganisms in a way that confers a health benefit. Many prebiotics are types of fibre. Foods containing fermentable fibres include onions, garlic, leeks, oats, legumes, bananas and a wide range of vegetables.
Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.
Fermented foods are foods transformed by microorganisms. Some contain live microbes at the point we eat them and some do not. Yoghurt with live cultures, kefir, kimchi and unpasteurised fermented vegetables can all add different foods and microbial exposures to the diet.
The evidence around probiotics and respiratory infections is interesting but should be described carefully. A Cochrane review of 23 trials involving 6,950 participants across children and adults found that probiotics may reduce the likelihood and incidence of acute upper respiratory tract infections and may shorten their duration. That means there is some evidence supporting further interest in probiotics to help ward off illness, rather than proving that any specific probiotic will prevent your child catching a cold.
Where microbz kids fits
Microbz kids is our living, liquid fermented probiotic developed specifically for children. It contains a diverse community of 15 probiotic cultures and is fermented with a blend of herbs, juices and minerals, including chamomile, echinacea and carob.
We see it as one part of a bigger picture: alongside a varied diet, plenty of fibre, good sleep, outdoor movement and the everyday hygiene measures that reduce the spread of infection. It is not a medicine and we would not describe it as a guarantee against school bugs but we do have a growing number of parents who are thanking us because their children are no longer ill and off school.
If you choose to use a probiotic supplement for your child, follow the product directions and speak to an appropriate healthcare professional if your child has a medical condition, is immunocompromised or you have any concerns about supplementation. You can also send an email to our nutritionist here and she will provide free advice.
3. Do not forget vitamin D
Vitamin D has important roles in normal immune function as well as bone and muscle health. In the UK, sunlight is our main natural source, which becomes a problem as the days shorten.
Current NHS guidance says children aged one to four should have a daily supplement containing 10 micrograms of vitamin D. Government guidance also advises people aged four and over to consider a daily 10 microgram vitamin D supplement during autumn and winter. Babies have separate guidance depending on breastfeeding and the amount of infant formula they consume.
Food sources include oily fish, egg yolks and fortified foods, but it can be difficult to obtain enough vitamin D from food alone. Check age-specific NHS advice or ask a pharmacist, health visitor or GP if you are unsure.
4. Vitamin C matters, but food comes first
Vitamin C contributes to normal immune function and also helps the body absorb iron. The good news is that it is readily available in everyday foods including peppers, strawberries, kiwi fruit, oranges, broccoli and tomatoes.
Rather than reaching automatically for high-dose supplements, build vitamin C-rich foods into normal meals and snacks. A strawberry-and-oat breakfast, pepper strips in a lunchbox or broccoli with dinner all count. Again, variety wins.
5. Protect sleep as the school routine returns
The first weeks back at school can be exhausting. Earlier mornings, new social situations, after-school activities and the abrupt end of summer routines all change sleep.
Sleep is not dead time for the immune system. Research has linked shorter sleep with a greater likelihood of upper respiratory tract infections, although much of the evidence is observational and cannot prove that sleep alone causes or prevents infection. More broadly, adequate sleep is consistently associated with better physical, emotional and cognitive health in children.
The practical point is simple: bring bedtime back gradually before term begins if it has drifted over the holidays. Keep the routine predictable, reduce stimulating screens close to bedtime and give children enough opportunity to sleep for their age.
6. Get outside and move
Walking or cycling to school, playing outside after school or simply spending time in the garden can support physical health, sleep and wellbeing. Regular physical activity is part of a healthy childhood and does not need to look like organised exercise.
There is another reason we like this one. Childhood should include contact with the living world. Our relationship with microbes is not limited to a probiotic bottle or even to the gut. We encounter microbial communities through food, other people, animals and the natural environment. Research into how these environmental exposures influence the developing microbiome and immune system is still evolving, but it is an exciting area of science.
7. Keep the boring things that work
Microbiome science is fascinating, but it should not distract us from basic infection control. Hand washing with soap and water remains important, particularly before eating and after using the toilet. Children should learn to cover coughs and sneezes and to dispose of tissues. If they are unwell, follow current NHS and school guidance about when they should stay at home.
Norovirus is a useful reminder that 'antibacterial' is not the same as 'anti-infective'. Norovirus spreads extremely easily, and soap-and-water handwashing is particularly important. Good hygiene does not require trying to sterilise every surface or eradicate every microbe from a child's environment.
A famous study from Finland replaced sterile pavement, gravel and rubber yards in urban daycares with forest floor, soil, and plants. After just 28 days, Children aged 3 - 5 showed dramatically increased microbial diversity on their skin and guts and alongside better regulated immune markers.
Back to school is an immune-system workout, not a failure
There is a temptation to see every cold as evidence that a child's immune system needs 'boosting'. But children are meeting viruses they have not encountered before. The NHS notes that young children gradually build immunity and tend to get fewer colds as they get older.
Rather than asking yourself 'how do I stop my child ever getting ill?' try 'how do I support the foundations of health while their immune system is learning?'
That means nourishing the gut microbiome with a varied, fibre-rich diet, paying attention to vitamin D, protecting sleep, encouraging movement and time outside, practising sensible hygiene and, if you choose to use one, thinking of a probiotic as one part of that wider ecosystem rather than a magic shield.
At microbz, that word ecosystem matters to us. Human health does not happen in isolation. We are communities of human cells and microbial life, constantly responding to our food, our environment and each other. Back-to-school season makes that relationship particularly visible.
Thirty children may walk into the same classroom in September. They will not all respond in exactly the same way. We cannot control every virus they meet, but we can help create the conditions in which their growing bodies, microbiomes and immune systems are well supported for the term ahead.
A note for parents
This article is for general information and is not a substitute for medical advice. If your child is repeatedly or unusually unwell, has symptoms that concern you, has an underlying health condition, or you are unsure about supplements, speak to your GP, pharmacist or another qualified healthcare professional.
References
Cochrane Acute Respiratory Infections Group (2022) ‘Probiotics for preventing acute upper respiratory tract infections’, Cochrane Database of Systematic Reviews. Available via PubMed: https://pubmed.ncbi.nlm.nih.gov/36001877/
Das, R., Thatal, B. and Tamang, B. (2026) ‘Dietary fiber in pediatric gastrointestinal health: a narrative review of evidence and challenges’, Clinical and Experimental Pediatrics, 69(6), pp. 456–472. https://pubmed.ncbi.nlm.nih.gov/42198920/
Department for Education (2026) Pupil attendance in schools: autumn term 2025/26. GOV.UK Explore Education Statistics. https://explore-education-statistics.service.gov.uk/find-statistics/pupil-attendance-in-schools/2026-week-2-autumn-term-25-26
Department for Education (2026) Pupil absence in schools in England: academic year 2024/25. GOV.UK Explore Education Statistics. https://explore-education-statistics.service.gov.uk/find-statistics/pupil-absence-in-schools-in-england/2024-25
NHS (2024) Colds, coughs and ear infections in children. https://www.nhs.uk/baby/health/colds-coughs-and-ear-infections-in-children/
NHS (2024) Vitamins for children. https://www.nhs.uk/baby/weaning-and-feeding/vitamins-for-children/
Patel, S. et al. (2022) ‘Benefits of dietary fibre for children in health and disease’, Archives of Disease in Childhood. https://pubmed.ncbi.nlm.nih.gov/35277379/
Venter, C. (2023) ‘Immunonutrition: Diet Diversity, Gut Microbiome and Prevention of Allergic Diseases’, Allergy, Asthma & Immunology Research, 15(5), pp. 545–561. https://pubmed.ncbi.nlm.nih.gov/37827976/
Venter, C. et al. (2022) ‘Role of dietary fiber in promoting immune health: An EAACI position paper’, Allergy. https://pubmed.ncbi.nlm.nih.gov/35801383/
Prather, A.A. et al. / systematic review evidence summarised in: ‘The relationship between duration and quality of sleep and upper respiratory tract infections: a systematic review’ (2021). https://pubmed.ncbi.nlm.nih.gov/33997896/
