Food intolerance in children

The IgG-based tests sold direct to parents - and they're widely marketed, often professional-looking, and not cheap - have no good evidence base. The British Dietetic Association, the British Society for Allergy and Clinical Immunology, the European Academy of Allergy and Clinical Immunology, and every credible allergy body I'm aware of has stated this clearly.

As those bodies explain, IgG antibodies to foods are a normal part of the immune response. Having IgG antibodies to a food simply means you've eaten that food. It doesn't indicate intolerance. These tests commonly flag multiple foods as 'positive', leading families to restrict their child's diet unnecessarily - sometimes severely. Children are sometimes put on diets restricted to fewer than ten foods based on a commercial test result, with no clinical basis for any of the restrictions.

This can lead to nutritional deficiencies, eating anxiety, and sometimes missed genuine diagnoses (the symptoms attributed to 'intolerance' sometimes turn out to be coeliac disease or IBD that wasn't investigated because everyone assumed it was 'food intolerance'), and money wasted on testing that doesn't deliver what it promises.

Lactose intolerance is the most common genuine food intolerance and it deserves its own discussion. Primary lactose intolerance develops as lactase enzyme activity naturally decreases after weaning - this happens to most of the world's population to some degree, but the timing and severity vary by ethnicity and genetics. In the UK, it's less common than in many other populations but it's still not rare, particularly in children of Asian, African, Middle Eastern or Southern European heritage.

Secondary lactose intolerance can also develop temporarily after a gut infection, during active coeliac disease, or during IBD flares - the gut lining is damaged and lactase production drops until it heals. This is usually temporary and resolves as the gut recovers.

Identifying it involves a structured dietary trial and reintroduction — straightforward in principle but best guided by a dietitian to ensure the diet stays nutritionally adequate throughout. A consultation walks you through the process and interprets the results clearly.

Beyond lactose, common areas of concern include dairy protein (different from lactose - this is an immune reaction and therefore an allergy, not an intolerance), gluten (which should always prompt coeliac testing first), FODMAPs (fermentable carbohydrates that can cause gut symptoms in sensitive individuals), and histamine.

For any suspected intolerance, the approach is the same: structured elimination, careful monitoring, and planned reintroduction. These protocols need to be practical for families and nutritionally safe, which is why professional guidance matters. A consultation gives you a clear plan — what to remove, what to eat instead, what to monitor, and how to reintroduce — tailored to your child.

The other thing I always check is whether the symptoms might have a different explanation entirely. Functional abdominal pain, constipation, stress-related gut symptoms, and genuine conditions like coeliac disease (see Coeliac UK for further information) or IBD can all present with symptoms that get labelled 'food intolerance'. Making sure we're not missing something important is part of the assessment.