Food Intolerance in Children: What Parents Should Know
How to spot possible food reactions without cutting out half your child's diet
'My tummy hurts.'
Four small words every parent hears. Usually just as you are leaving for school, sitting down to dinner or finally getting everyone into bed.
Most childhood tummy aches are short-lived. But when the bloating, loose stools, constipation, headaches, skin flare-ups or tiredness keep returning, it is natural to wonder whether food is involved.
The difficult part is that food intolerance, food allergy, coeliac disease, reflux, constipation, infection and ordinary childhood eating patterns can look surprisingly similar. Removing foods at random might appear to be the quickest answer, but in a growing child it can create nutritional gaps, and may make the real cause harder to identify.
Contents
Food intolerance, food allergy or coeliac disease
Common signs of food intolerance in children
The symptom timing parents should record
Common food intolerances and lookalikes
What else can look like food intolerance
When should you speak to your GP
How food intolerance is investigated in children
A note about food intolerance testing
Why DIY elimination diets can backfire
Seven practical steps parents can take now
Making safe food swaps
How FIT can support your family
FAQs
Food intolerance, food allergy or coeliac disease
These terms are often used interchangeably online. Clinically, they mean very different things.
Food intolerance. A food intolerance usually involves difficulty digesting or processing a food or one of its components. It does not cause anaphylaxis. Symptoms are often dose-dependent and may appear several hours after eating, which makes patterns difficult to spot.
Lactose intolerance is a familiar example: insufficient lactase enzyme means lactose is not fully digested, leading to wind, bloating, cramps or diarrhoea. Some children tolerate a small amount but react to a larger portion.
Food allergy. A food allergy involves the immune system. IgE-mediated reactions often begin within minutes to two hours and may cause hives, swelling, vomiting, wheezing or breathing problems.
Non-IgE-mediated food allergy can be delayed and may look more like intolerance, with eczema, vomiting, diarrhoea, constipation, reflux, feeding difficulties or poor growth.
Important: sudden swelling of the lips, mouth, tongue or throat, breathing difficulty, collapse, marked drowsiness or a rapidly worsening reaction requires emergency help. Call 999 and use prescribed adrenaline immediately according to your child's allergy action plan.
Coeliac disease. Coeliac disease is an autoimmune condition triggered by gluten. It can cause gut symptoms, fatigue, iron deficiency, mouth ulcers, poor growth and many less obvious symptoms. It is neither an allergy nor an intolerance.
Do not remove gluten before coeliac testing. Blood tests may be inaccurate once gluten has been reduced. Speak to your GP while your child is still eating gluten and continue it during the diagnostic process unless their medical team advises otherwise.
Common signs of food intolerance in children
There is no single 'food intolerance symptom.' Look for a repeatable pattern rather than one bad day.
Recurring tummy pain, cramping or bloating
Excessive wind
Loose stools or diarrhoea
Constipation or changes in stool pattern
Nausea
Headaches
Unexplained tiredness or reduced energy
Mouth ulcers
Symptoms that appear after a larger, but not necessarily a tiny, amount of a particular food
Mood, concentration and sleep can change when a child feels uncomfortable, but these symptoms are non-specific. Irritability after lunch does not prove a food reaction. The more useful clue is whether the same combination of food, timing and physical symptoms repeats.
The symptom timing parents should record
What was eaten and drunk, including sauces, snacks and portion sizes
What time it was eaten
When symptoms began and how long they lasted
Bowel frequency and stool appearance
Skin, breathing or swelling symptoms
Sleep, stress, illness, medication and activity
Whether the same food has been tolerated at other times
A two-week diary often reveals more than a list of 'good' and 'bad' foods. It can show whether symptoms relate to portion size, constipation, rushed eating, school-day anxiety, a stomach bug or several ingredients eaten together.
Common food intolerances and lookalikes
Lactose intolerance. Can cause wind, bloating, cramps and diarrhoea after dairy containing lactose. It can be temporary after gastroenteritis because lactase sits on the gut lining and may fall while the intestine recovers. Lactose intolerance is different from cow's milk protein allergy, and many hard cheeses contain very little lactose.
Fructose and other fermentable carbohydrates. Some children struggle with large amounts of fructose or other fermentable carbohydrates. Fruit juice, dried fruit, apples, pears, onions, garlic, wheat-based foods and some sweeteners can contribute to bloating or altered stools in susceptible children. That does not mean all these foods should be removed together.
Wheat or gluten symptoms. Symptoms after bread or pasta might relate to coeliac disease, wheat allergy, wheat fructans, portion size or another part of the meal. Coeliac disease and allergy need appropriate medical assessment before a 'gluten intolerance' label is applied.
Food additives. Some additives or naturally occurring food chemicals may trigger symptoms in a small number of children, but broad additive-free or low-histamine diets can become extremely restrictive. These should not be a first-line DIY experiment.
What else can look like food intolerance
Constipation, even when a child still passes stool regularly
Reflux or functional abdominal pain
Coeliac disease
IgE- or non-IgE-mediated food allergy
A stomach infection or temporary post-infectious lactose intolerance
IBS or altered gut fermentation
Inflammatory bowel disease
Medication effects
Anxiety, school stress or disrupted sleep
Eating very quickly, large portions or excessive fruit juice
This is why symptoms alone cannot give a reliable diagnosis.
When should you speak to your GP
Book a GP appointment when symptoms keep returning, interfere with school or sleep, or lead you to consider removing a major food group. Seek prompt medical assessment for:
Weight loss, faltering growth or delayed puberty
Blood or black colour in the stool
Persistent vomiting or diarrhoea
Severe or localised abdominal pain
Difficulty swallowing or food becoming stuck
Persistent fever, marked lethargy or dehydration
Iron deficiency, pallor or unexplained fatigue
Night-time symptoms that repeatedly wake your child
A strong family history of coeliac disease, inflammatory bowel disease or severe allergy
How food intolerance is investigated in children
There is no single test that diagnoses every food intolerance. The appropriate route depends on the suspected mechanism.
Start with a detailed history. Timing, dose, repeatability, growth, eczema, asthma, bowel pattern and family history guide the next step.
Exclude medical conditions first. Your GP may consider coeliac screening, allergy assessment, stool tests, blood tests or referral depending on symptoms.
Use targeted testing where appropriate. Hydrogen breath testing can sometimes help assess lactose or fructose malabsorption. Skin-prick or specific-IgE blood tests assess immediate allergy, not food intolerance.
Trial one structured change. For suspected delayed food allergy, NICE describes a two- to six-week elimination followed by planned reintroduction, with appropriate dietetic guidance. Intolerance trials should also be targeted and time-limited.
Reintroduce. Improvement during avoidance is only half the information. A planned reintroduction helps determine whether the food genuinely caused the symptoms and what amount is tolerated.
A note about food intolerance testing
No food intolerance panel can diagnose coeliac disease or an IgE-mediated food allergy. Those require the correct medical pathway.
At FIT, any testing is interpreted alongside the child's symptom history, current diet, growth, medical investigations and nutritional requirements. A result is never a licence to remove multiple foods indefinitely. The value lies in expert interpretation, a focused plan and structured reintroduction, not simply receiving a list of foods.
If a child has rapid reactions, breathing symptoms, swelling, severe eczema, poor growth, blood in the stool or suspected coeliac disease, medical and specialist assessment takes priority.
Why DIY elimination diets can backfire
Children are building bones, muscle, organs and brains. Removing dairy, wheat, eggs or several foods together can reduce energy and protein, calcium and iodine, iron and B vitamins, vitamin D, fibre and microbiome diversity, and confidence and flexibility around food.
Restriction can also increase anxiety at parties, school dinners and family meals. The aim is not to create a 'perfect' diet. It is to identify the smallest necessary change while keeping your child nourished and included.
Seven practical steps parents can take now
Do not remove several foods at once. You will not know which change helped.
Keep a detailed 14-day diary before changing the diet, unless a clinician has advised immediate avoidance for safety.
Photograph labels and meals. Brand recipes change and hidden ingredients matter.
Check growth. Record recent height and weight and share any changes with your GP or practitioner.
Replace before you remove. Plan the nutritional substitute first, especially for milk, wheat or multiple staple foods.
Tell school or nursery only what is known. Keep suspected intolerance separate from diagnosed allergy and provide a formal allergy action plan where required.
Review and reintroduce. A childhood diet should not remain restricted by default when tolerance may change.
Making safe food swaps
If dairy is removed, choose an age-appropriate fortified alternative providing calcium and iodine where possible; many organic plant drinks are not fortified. Rice drinks are not recommended as a main milk drink for children under five because of arsenic levels. Children under two need individual professional guidance before replacing breast milk or formula.
If wheat is removed after appropriate screening, maintain fibre and energy with foods such as certified gluten-free oats, potatoes, rice, quinoa, buckwheat, corn, pulses, nuts and seeds as age-appropriate and tolerated.
If eggs or several proteins are removed, deliberately replace protein, iron, choline and other nutrients rather than relying on 'free-from' snack products.
How FIT can support your family
Parents do not need another confusing list from the internet. They need a clear sequence, sensible safeguards and meals their child will actually eat.
FIT support may include a detailed review of symptoms, diet, bowel patterns and medical history, guidance on which concerns should go back to the GP or allergy team, a targeted, not blanket, testing strategy where appropriate, a nutritionally complete elimination and reintroduction plan, family-friendly meal, lunchbox and snack ideas, and support interpreting labels and managing school, parties and eating out.
Not sure where to start? Book a free 15-minute Personalised FIT Health Review or explore FIT testing and consultation packages. Our Advanced Food Intolerance Assessment can support a targeted, expert-interpreted approach where testing is appropriate.
For practical food ideas, visit the FIT Recipe Hub. For persistent bloating and bowel changes, read What Is Gut Dysbiosis?
Frequently Asked Questions
Can a child suddenly develop a food intolerance? Yes. Tolerance can change, and temporary lactose intolerance can follow gastroenteritis. But new symptoms should still be assessed rather than assumed to be food-related.
What is the most common food intolerance in children? Lactose intolerance is one of the best recognised, although prevalence varies by age and ethnicity. Cow's milk allergy is different.
Can food intolerance cause behaviour problems? Pain, poor sleep or urgent bowel symptoms can affect mood and concentration, but behaviour change alone does not diagnose intolerance.
Should I cut out gluten if my child has tummy aches? No. Discuss coeliac testing with your GP first while your child is still eating gluten.
Can my child grow out of an intolerance? Some intolerances are temporary or dose-dependent. Review and planned reintroduction help avoid unnecessary lifelong restriction.
Can a food intolerance test diagnose an allergy? No. Immediate food allergy requires an allergy-focused clinical history and, where appropriate, skin-prick or specific-IgE testing interpreted by a qualified clinician.
References:
NHS. Food intolerance.
NHS. Food allergy.
NICE. Food allergy in under 19s: assessment and diagnosis (CG116).
NICE. Diagnosing non-IgE-mediated food allergy (QS118).
Raising Children Network. Food intolerance in children and teenagers.
Coeliac UK. Getting diagnosed.
Don’t forget to pin it.
The FIT takeaway
Recurring symptoms deserve attention, but not panic, blame or a fridge full of unnecessary 'free-from' food.
Record the pattern. Rule out allergy and coeliac disease. Protect growth and nutritional adequacy. Change one thing at a time. Then reintroduce with purpose.
Because the goal is not simply to remove a food. It is to help your child feel well, eat confidently and thrive.
Take the free Find Your FIT Quiz to discover which test or programme suits your symptoms, or book a free 15-minute Personalised FIT Health Review with Becki for a direct, no-obligation conversation about where to start.
About Becki Hawkins
Becki Hawkins, BSc (Hons), mBANT, CNHC, is the founder of FIT Nutrition & Testing Clinic and a Registered Nutritional Therapist with over 20 years of experience. She specialises in evidence-based personalised nutrition and functional testing, helping clients uncover the root causes of digestive issues, hormonal imbalances, and unexplained symptoms. Becki combines clinical expertise with culinary creativity, translating complex test results into practical, delicious nutrition plans that work in real life. Her approach is simple: test, don't guess. Because guessing doesn't heal. Knowing does.