For roughly two decades, parents were advised to keep peanut and egg away from babies for as long as possible. That advice turned out to be not merely useless but backwards — and it is still being repeated by people who love you and mean well.
The old logic was intuitive: if a food can cause a reaction, keep it away until the child is stronger. In the early 2000s this was formal public health advice in both the UK and the United States.
Rates of peanut allergy rose anyway. Then somebody noticed something awkward — Jewish children in Israel, where a peanut-based snack is given to babies almost universally, had a fraction of the peanut allergy seen in Jewish children in London, where it was being carefully avoided. Same genetics, opposite outcomes.
The LEAP trial tested it directly, and the result was decisive enough to change guidance internationally. Early, regular exposure did not cause allergy. It substantially prevented it. Avoidance had been the thing driving the problem.
Introduce the common allergens from around six months, once your baby is showing the signs of readiness for solids — and once introduced, keep them in the diet regularly. Roughly once or twice a week is enough. Dropping a food out again for several weeks can allow sensitivity to develop.
Delaying beyond six to twelve months now appears to increase the risk of developing an allergy rather than reduce it.
UK law requires fourteen allergens to be declared on food. For weaning, four do most of the work: peanut, tree nuts, egg and cow's milk.
| Allergen | How to give it to a baby |
|---|---|
| Peanut | Smooth peanut butter thinned with warm water, milk or yoghurt. Or finely ground peanut stirred into purée. Never whole nuts, never a spoonful of thick butter. |
| Tree nuts (almond, cashew, walnut, hazelnut) | Smooth nut butters thinned down, or ground finely into food. Same rule — never whole, until at least five. |
| Egg | Well-cooked to start with — hard-boiled yolk is ideal. British Lion mark eggs may be given soft-cooked from six months; without the Lion mark, cook until solid throughout. |
| Cow's milk | In food from six months — yoghurt, cheese, milk in cooking. Not as a main drink until twelve months. |
| Wheat / gluten | Toast fingers, pasta, cereal. No reason to delay. |
| Sesame | Tahini thinned into food, or houmous. |
| Soya | Tofu, or soya yoghurt. |
| Fish and shellfish | Well cooked and meticulously boned. Shellfish thoroughly cooked, never raw. |
The others — celery, mustard, lupin, molluscs and sulphites — are far less common in a baby's diet and need no special scheduling. Introduce them as they naturally come up in family food.
If there is a reaction you need to know what caused it. Leave two or three days between new allergens.
Not at nursery, not at a party, not at bedtime. You want to be able to watch them for a few hours afterwards, awake, with nothing else going on — and with a clear head if you need to act.
A quarter of a teaspoon, mixed into something they already eat happily. Rub a little on the inside of the lip first if you want to be cautious, and wait a few minutes.
Quarter teaspoon, then half, then a teaspoon. There is no rush, but there is no reason to crawl either.
This is the part most often missed. Once introduced without a problem, that food needs to stay in the diet regularly — once or twice a week. Introducing peanut at six months and then not giving it again until they are two undoes much of the benefit.
Severe eczema in early infancy is the single strongest predictor of food allergy, and these are the babies for whom early introduction matters most — but also the ones where it is worth having a conversation first. Speak to your GP or health visitor before you start. They may want to introduce allergens under supervision, or refer you. Do not simply avoid: that is the response that made the problem worse in the first place.
Most reactions are mild, and most appear within minutes to two hours of eating.
What to do: Stop the food. Antihistamine if your GP has advised one. Contact your GP for advice and to arrange assessment before trying it again.
Call 999 and say anaphylaxis. Lie them flat with legs raised. If an adrenaline auto-injector has been prescribed, use it immediately — do not wait to be certain.
Not every food allergy is immediate. Non-IgE reactions can appear hours or even a couple of days later, most often as reflux, persistent loose or mucousy stools, blood in the stool, worsening eczema, or a baby who is simply miserable and not gaining weight. These are easily missed and easily dismissed. If a pattern keeps repeating with the same food, keep a written diary of what and when, and take it to your GP.
Plenty of ordinary weaning events get read as allergic reactions and are not.
If you are unsure whether something was a reaction, take a photograph. A picture of a rash is worth far more to a GP than a description of one three days later.