Advice on preventing food allergy changed substantially following trial evidence, and the reversal is worth understanding since older advice still circulates.
The previous guidance
For a period, guidance in several countries recommended delaying introduction of allergenic foods.
Which was based on reasoning rather than on trial evidence, and allergy rates continued rising during the period it was in force.
What changed it
An observation that allergy to a specific food was much less common in a population where it was introduced early than in a comparable population where it was avoided.
Which prompted a randomised trial that found early introduction substantially reduced allergy development in high-risk infants.
Subsequent trials examined other foods with results supporting earlier introduction.
Guidance in several countries changed accordingly.
The current position
National guidance now generally recommends introducing allergenic foods during the weaning period rather than delaying, alongside other foods.
Specific recommendations differ between countries, particularly regarding infants at higher risk who may be advised to seek medical advice first.
Which means the guidance for your country is what should be followed, and it is published by the relevant health service.
The dual allergen exposure hypothesis
The leading explanation for how allergy develops.
Exposure through damaged skin, particularly in eczema, may promote sensitisation.
Exposure through the gut may promote tolerance.
Which would mean that a child with eczema encountering a food on their skin before eating it is at higher risk, and it explains why eczema is a strong risk factor.
Evidence is consistent with the hypothesis and it is not fully established.
Allergy against intolerance
Distinct mechanisms frequently confused.
Allergy involves an immune response and can cause rapid severe reactions.
Intolerance involves difficulty digesting a food and causes discomfort rather than immune reaction.
Which matters because the management differs entirely, and because self-diagnosed intolerance leading to unnecessary exclusion carries nutritional risk in children.
Testing
Skin prick and blood tests measure sensitisation rather than clinical allergy.
Which means a positive test in someone who eats the food without reaction does not indicate allergy, and testing without clinical suspicion produces misleading results.
This is why untargeted testing is not recommended, and why diagnosis requires clinical assessment and sometimes supervised challenge.
Commercially marketed intolerance tests measuring various markers have no established validity and are not recommended by allergy organisations.
Anaphylaxis
A severe rapid reaction requiring immediate treatment with adrenaline and emergency medical help.
Children at risk are prescribed auto-injectors, and training in their use for the child, family and school is essential.
Which includes knowing that adrenaline should be given early rather than held back, and that emergency services should always be called even if symptoms improve.
Where to get advice
Any suspected allergy should be assessed by a doctor rather than managed through elimination.
This describes how the evidence developed and is not clinical advice, and decisions about introducing foods to an individual child should involve a health professional where there is any risk factor.
Eczema
The strongest single risk factor for food allergy development.
Which has driven interest in whether treating eczema effectively reduces allergy development, with trials producing mixed results.
Effective eczema management is worthwhile regardless, and undertreatment with topical steroids due to unfounded fear is documented and causes avoidable suffering.
Outgrowing allergies
Several common childhood allergies are frequently outgrown, with rates varying substantially by allergen.
Which is why periodic reassessment is part of allergy care, and why lifelong avoidance should not be assumed without review.
Others are more commonly lifelong.
Immunotherapy
Controlled exposure under medical supervision to build tolerance.
Which has evidence for some allergens and is done only in specialist settings, since reactions occur.
It should never be attempted independently, and unsupervised reintroduction of a known allergen is dangerous.
School and settings
Allergy management plans, staff training and access to emergency medication are what make a setting safe.
Which parents can ask about specifically rather than assuming, and requirements differ by jurisdiction.
Breastfeeding
Its relationship with allergy development has been studied extensively with mixed findings.
Which means the evidence does not support strong claims about allergy prevention specifically, and breastfeeding is recommended for other well-established reasons.
Maternal avoidance of allergenic foods during pregnancy or breastfeeding is not recommended for allergy prevention, having been examined and not supported.
Environmental allergies
Distinct from food allergy, covering pollen, dust mites, animals and moulds.
Which develop on a different timescale and are managed differently, generally through avoidance where practical and medication.
Asthma frequently coexists, and asthma management is a separate matter with its own guidance that should be followed closely.
Labelling
Regulations require specified allergens to be declared, with rules on emphasis in ingredient lists.
Precautionary statements about possible cross-contamination are generally voluntary and unstandardised, which makes them difficult to interpret.
Reading labels
Ingredient lists rather than front-of-pack claims, since formulations change and previous safety does not guarantee current safety.
Which means checking every time rather than once, particularly for products bought regularly.