How to introduce allergens

Why early, and why keep going

For years, parents were told to hold back foods like peanut and egg. Newer research found that waiting doesn’t prevent food allergy, and may make it more likely. A 2021 consensus from US and Canadian allergy societies recommends introducing both peanut and egg around 6 months, but not before 4 months, and introducing the other common allergens around the same time. The NHS also says delaying peanut and egg beyond 6 to 12 months may increase the risk of allergy to them.

Getting started is only half of it. Once your baby tolerates a food, keeping it in their diet regularly is what matters. The study behind the US peanut guidelines found that early peanut, with continued, regular servings, prevented peanut allergy in high-risk babies.

A varied diet in the first year may also help, according to the consensus. And if you’re breastfeeding, you don’t need to avoid allergens yourself unless you’re allergic to them.

The common allergens

In the US, the 9 major food allergens are peanut, tree nuts, egg, milk, wheat, soy, sesame, fish and shellfish. The NHS list for babies also includes foods with gluten (wheat, barley and rye), beans, lentils and peas, seeds, celery, mustard, and sulphur dioxide (sulphites), which is sometimes found in dried fruit and fruit juice.

See the safe first form of each allergen, and the full guides for egg and fish like salmon.

Talk to your doctor first if…

• your baby has severe eczema, or eczema that’s hard to control
• your baby has an egg allergy, has already had an allergic reaction to a food, or has another diagnosed food allergy

These babies have a higher chance of peanut allergy. US guidelines recommend they’re checked by their pediatrician or an allergist, sometimes with allergy testing, before peanut is introduced. Early introduction, often around 4 to 6 months, matters most for them, so ask soon. Don’t give the first peanut at home until your doctor has told you how.

For most other babies, the consensus says allergy testing is not required before you start.

How to offer a new allergen

1. Start with a few low-risk foods first. The AAP suggests foods like infant cereal or puréed fruit, so you know your baby is managing solids.
2. Pick a good day. Choose a day your baby is well, at home, when you can watch them for a couple of hours afterward.
3. Offer a small amount in a safe form, mixed into a food your baby already eats. For example, stir a little smooth peanut butter into infant cereal or purée, thinned with breast milk, formula or water.
4. One new allergen at a time. Wait a few days before the next new food, so you can tell what caused any reaction. The CDC suggests 3 to 5 days between new foods.
5. Keep it going. If there’s no reaction, increase the amount gradually and keep offering it as part of your baby’s usual meals.

Safe forms, and what to avoid

• Peanut and tree nuts: smooth nut butter thinned, or stirred into food, or peanut powder or finely ground nuts mixed in. Never whole or chopped nuts, and never spoonfuls of thick nut butter: they’re choking hazards. The AAP says not to give whole peanuts or tree nuts to babies or young children, and to wait for whole peanuts until at least 4 years; the NHS says no whole nuts under 5. Brazil nuts are the exception: one nut can have more selenium than the NIH upper limit for a baby up to 6 months, so they wait until 7 months, and then only a tiny finely grated amount. Use another tree nut for the first taste.
• Egg: well-cooked, such as hard-boiled and mashed, or a fully cooked omelet cut into strips.
• Milk: plain full-fat yogurt; pasteurized hard cheese like mild cheddar, grated or in thin slices; cottage cheese or cream cheese; or cow’s milk in cooking. Not as a main drink until 12 months. No chunks of cheese, and no brie, camembert or soft blue cheese.
• Soy: soft tofu strips or mashed tofu, or plain soy yogurt.
• Sesame: tahini thinned or stirred into food, or finely ground seeds. No whole seeds sprinkled on top.
• Wheat: well-cooked pasta, soft toast strips, or wheat infant cereal. No whole wheat kernels, or bread and crackers with whole seeds or nuts.
• Fish and shellfish: fully cooked. Fish flaked and checked for bones; shrimp finely minced into soft food (small pieces from around 9 months). Never raw or lightly cooked.

How much to keep offering

The AAP gives these examples of a regular portion once a food is tolerated: about 2 teaspoons of peanut butter or another nut or seed butter (thinned or spread thinly, never on its own), or about ⅓ of a well-cooked egg. Offer these as part of normal meals, not as a test you repeat once.

Signs of an allergic reaction

Reactions usually start within minutes of eating, but can take up to 2 hours. Some, like cow’s milk allergy, can take up to 3 days.

Mild to moderate: hives or a red, itchy rash, especially around the mouth; mild puffiness of the face or around the eyes; vomiting once, tummy pain or diarrhea; sneezing or a runny nose; eczema getting worse. If it’s only one of these, stop offering the food, stay with your baby and watch them closely for the next couple of hours, and call your pediatrician before you try it again. If signs show up in more than one part of the body at once, treat it as severe (below). Don’t cut out a major food like milk for good on your own: ask your doctor, who may refer you to a dietitian.

Severe (anaphylaxis): trouble breathing, wheezing, or a cough that won’t stop; swelling of the tongue or throat, lips or mouth that suddenly swell, a hoarse cry, drooling or trouble swallowing; turning pale or floppy, or very sleepy or unresponsive; or signs in more than one part of the body at once, such as hives with repeated vomiting.

If your baby has an epinephrine (adrenaline) auto-injector, use it right away, then call for an ambulance. Call 911.Call 999.Call your local emergency number (such as 112 in Europe or 000 in Australia). If you don’t have an auto-injector, call straight away. Keep your baby lying down, never standing or walking (on their side if they’re vomiting, head and shoulders a little raised if breathing is hard), and go to hospital even if they seem better. See signs of anaphylaxis.

Where US and UK advice differs

• Who should check with a doctor first. US guidelines single out babies with severe eczema, egg allergy or a previous food reaction. The NHS also advises talking to your GP or health visitor first if your baby has any eczema, or if there’s a family history of food allergy, eczema, asthma or hay fever.
• Runny eggs. In the US, eggs for babies should be fully cooked. The NHS says hens’ eggs with the British Lion stamp are safe for babies raw or lightly cooked. Other eggs, including duck, goose and quail, should be cooked until the white and yolk are solid.
• Nut butter. The AAP suggests thinning peanut butter into cereal, purée or yogurt. The NHS says to spread it onto a food such as toast (we suggest spreading it thinly). Both say never give it on its own.
• Waiting between foods. The CDC and the AAP’s starting solids guide suggest 3 to 5 days between new foods (the AAP’s allergen guide says at least a day). The NHS doesn’t set a number: it says one at a time, so you can spot a reaction.

Ready for the next step? See what to feed at 6 months and the baby feeding schedule.