Feeding
Allergies and intolerances in the first year
Immediate and delayed reactions look completely different, and the difference determines what happens next.
Food allergy affects a meaningful proportion of infants, and a considerably larger proportion are placed on restricted diets without a diagnosis, which carries its own risks.
The two mechanisms
The distinction that determines everything else.
IgE-mediated allergy produces rapid reactions, typically within minutes to two hours: hives, swelling of lips, face or eyes, vomiting, coughing, wheeze, and in severe cases anaphylaxis.
It is what allergy tests detect.
Non-IgE-mediated allergy produces delayed reactions over hours to days: reflux-like symptoms, colic, blood or mucus in stools, chronic diarrhoea or constipation, eczema, food refusal and poor growth.
Skin prick and blood tests do not detect it, which is why testing frequently comes back negative in babies who genuinely have it.
Diagnosis is by supervised exclusion and planned reintroduction.
Anaphylaxis
The emergency, and worth knowing precisely.
Signs: difficulty breathing, noisy breathing or wheeze, swelling of the tongue or throat, hoarse voice, persistent cough, pale and floppy, or collapse.
Action: call emergency services immediately, lie the child flat with legs raised — or on their side if vomiting — and use adrenaline auto-injector if prescribed, into the outer thigh.
Do not stand the child up.
Anyone with a prescribed auto-injector should carry two, and everyone caring for the child should know how to use them.
Antihistamines treat mild reactions and do not treat anaphylaxis.
Cow's milk protein allergy
The most common infant food allergy, in both forms.
Management for formula-fed infants is an extensively hydrolysed formula, with amino acid formula for severe cases, prescribed rather than chosen.
For breastfed infants it is maternal exclusion of dairy with calcium and vitamin D supplementation and dietetic support.
Soya formula is not recommended under six months and a proportion of infants react to it as well.
Plant-based drinks are not adequate substitutes for infant formula.
Most children outgrow it, commonly within the first few years, which is why planned reintroduction under guidance — frequently using a milk ladder for non-IgE allergy — matters rather than indefinite avoidance.
Prevention
Where the advice reversed.
Introducing allergenic foods from around six months, alongside other solids, rather than delaying them, is now recommended in most guidance on the basis of trial evidence.
Once introduced, keeping them in the diet regularly matters, since tolerance requires continued exposure.
Infants with severe eczema or an existing food allergy are the highest-risk group and should discuss introduction with a clinician, since specialist advice or supervised introduction may apply.
Maternal avoidance of allergens during pregnancy or breastfeeding is not recommended for prevention.
Lactose intolerance
Frequently confused with milk allergy and quite different.
It is a digestive problem with the sugar in milk rather than an immune reaction to the protein.
Primary lactose intolerance essentially does not occur in infants, developing later in childhood or adulthood and varying substantially between populations.
Secondary lactose intolerance occurs temporarily after gastroenteritis and resolves.
Which means an infant with symptoms after milk is far more likely to have cow's milk protein allergy than lactose intolerance, and switching to a lactose-free formula will not help.
Testing
What is and is not valid.
Skin prick tests and specific IgE blood tests detect IgE-mediated allergy and are interpreted alongside the history — a positive test without symptoms indicates sensitisation rather than allergy, and acting on it can cause unnecessary exclusion.
Oral food challenge under supervision is the definitive test.
Not valid: IgG food intolerance tests, hair analysis, kinesiology, vega testing and similar, which are sold commercially and which allergy organisations advise against because they generate long lists of foods to avoid with no clinical basis.
The risks of unnecessary exclusion
Worth stating.
Restricted diets in infancy risk inadequate nutrition and growth, particularly where dairy is removed without replacement.
They increase family stress and cost.
They may reduce the chance of tolerance developing.
And they delay identification of the actual cause of symptoms.
Which is why exclusion should be a supervised, time-limited diagnostic step with a planned reintroduction, rather than a permanent decision made at home.
Living with a diagnosis
Practical points.
Learn to read labels, including for precautionary statements.
Inform nursery, family and anyone who feeds the child, in writing.
Have a written allergy action plan from the clinical team.
Carry medication where prescribed.
Get dietetic input, which is standard for infant food allergy and frequently omitted.
And arrange review, since most infant food allergies resolve and children are otherwise left avoiding foods unnecessarily for years.
General information only, not medical advice. Call emergency services for suspected anaphylaxis. Consult a clinician before excluding foods, and seek dietetic support for any diagnosed allergy.
