Food intolerances and allergies are increasingly hot topics. There’s no denying how many parents worry about potential allergy symptoms in their baby. But beware of self-diagnosis! It’s not uncommon for parents to compare their situation with other families, except that the reality is that every child is different, and a professional’s overall assessment of an infant may be quite different in the end, and recommendations may also vary as a result.

For babies fed commercial formulas, how many parents change milk formulas several times without knowing if their baby’s symptoms are really associated with food intolerance or allergies? How many breastfeeding moms think that their milk isn’t good for their baby? Too many!

Allergy Types

Two types of allergies exist—more acute types and more chronic types. Each person is different, so it’s unclear what quantities need to be absorbed or how frequently to provoke an intolerance or allergic reaction.

Acute Types

The acute form is better defined but less frequent. The baby can react within four hours after consuming milk. This allergy provokes automatic vomiting, sometimes diarrhea with mucus and possibly blood in their stool. However, before concluding an allergy in similar cases, according to the paediatrician Dr. Jack Newman, you have to examine your baby as a whole. Ensure that lower milk production isn’t the cause of the blood and mucus in the baby’s stool. You will notice this if you increase your breastfeeding frequency and the blood and/or mucus disappear. If this is the case, you have your answer.

Chronic Types

The chronic type is more frequent but less clear, with clinically vague symptoms. When you eliminate the allergen or sensitivity for 2–3 weeks and the baby’s symptoms disappear, this is a more chronic type of allergy.

First, few acute allergies to breast milk exist. A baby fed with their mother’s milk for the first four months of life has a much lower risk of developing allergies throughout their lives. This milk is better adapted to the baby’s immature gastrointestinal system because it’s easy to digest and absorb.

Diet to Prevent Allergies?

Initially, a pregnant or breastfeeding woman won’t have dietary restrictions to prevent allergies in their baby. Based on the latest research, no scientific evidence for the prevention of allergies with an elimination diet is available.

Milk protein allergies or allergies to bovine proteins contained in breast milk can rarely provoke intolerance or allergic reactions in a baby. Only then are there benefits to suggesting a diet for the mother.

The most frequent allergen remains cow milk which can lead to allergies to bovine proteins. It’s not easy to know what precise elements in the milk cause reactions. We often speak of hypersensitivity to an ingredient, a milk component difficult to identify.

First, the mother must adapt their diet, which will eliminate proteins from dairy products (milk proteins) for at least 10–14 days to see if there’s a change in the baby.

It’s preferable to eliminate one thing at a time to uncover the sensitive agent. If we remove too many things at a time, it will be difficult to identify the possible cause of the symptoms. Then, if necessary, remove soya followed by eggs. The first two foods (milk and soy) are by far the most likely to be involved in an infant’s intolerance or allergy.

Wheat, corn and animal-based proteins (ex.: beef) come next.

If the baby has a severe reaction to the food, the mother might also avoid foods that contain even traces of this ingredient, but only if necessary.

Current studies (2023) show that removing milk only from breastfeeding mothers reduces symptoms in babies by 47% after one to two weeks. Withdrawing soy thereafter reduces symptoms by a further 40%, and after egg restriction, if necessary, reduces symptoms in the baby by a further 13%. Hence the importance of taking it one step at a time, to avoid restricting the mother’s diet for nothing.

Although there is still a popular belief in the importance of removing lactose (milk sugar) from a breastfeeding mother’s diet in the event of intolerance in the baby, it is not recommended to avoid it unless the baby has a diagnosed liver problem.

To ensure her nutritional intake and eliminate any deficiencies if food restriction lasts several weeks or months, the addition of a vitamin supplement for the mother may be necessary—calcium, vitamin D, iron and sometimes proteins. Consulting a nutritionist who practices in pediatrics is also a very good idea for personalized guidance, based on your unique situation with your baby. After 3-6 weeks we will usually see a difference in the baby’s symptoms and it’s at 12 months that the vast majority of intolerances in infants are resolved.

Imagine a baby that reacts to their mother’s milk, which is easy to digest. How will they respond to the formula? You will need a very special formula which features partially hydrolyzed or completely deconstructed proteins where proteins are broken down into amino acids for very fragile and sensitive children. Depending on the baby’s reaction.

Lactose Intolerance or Allergy

Lactose (milk sugar) intolerance or allergy is very rare for babies and is often associated with family history and genetics. There’s about one case in 1 million.

In the latest research, this is a lactase deficit rather than lactose intolerance. This missing enzyme, which digests milk sugar (lactose), leads to reactions in newborns. It’s not a defence reaction by their immature immune system like with more severe food allergies. Even if you give the baby this enzyme orally, it seems to not really change anything. Given the infrequency of this situation, the mother doesn’t need to stop breastfeeding. However, we can suggest consulting to get proper support for the breastfeeding experience with the baby and be thoroughly evaluated.

Parents contact me regularly to say that they changed their baby’s formula three times over a three-week period because their baby is intolerant or allergic. Why do they say this? Because they noted that their baby cried at night or that their stool was a bit hard. Wrong! You shouldn’t self-diagnose intolerance or allergies in a baby and change their formula without getting a recommendation from a health professional. We note that many parents change the baby’s formula but remain in the same composition category. So, they changed the company, but they gave them similar milk.

The baby’s gastrointestinal system needs time to adapt to milk. Both for breast milk and formulas, the system must learn to digest it and absorb it. Generally, allergy signs develop over time. Repeated contact is needed to get these reactions. Most of the time, you will see reactions occur gradually over a few weeks. Are my baby’s reactions or discomfort normal? Alternatively, is it a food intolerance or allergy? Yikes! How can parents know?

What is a Food Allergy?

Allergy to a food

We talk about food allergies when there is an inadequate and excessive immune response following contact (by eating it) with an ingredient in a food (often proteins), which then repeats each time the food is consumed.

When a baby shows an allergy to a food, it is their immune system (the body’s defence mechanism which can be identified by IgE-mediated) that starts up. It is activated to fight an undesirable invader contained in this food and provokes a moderate to severe reaction each time the food is ingested. At the start, in a young baby, the reaction can be progressive during repeated contact with the allergen. The signs will be more automatic after a certain time. A mixed allergy can also be identified, with additional clinical signs such as skin reaction (e.g. eczema), esophagitis or gastritis (inflammation of the esophagus and/or stomach in response to allergen absorption).

A milk allergy is without a doubt more frequent in a baby as milk protein is the first given to a newborn and affects 2.5% of them.

In the case of a milk allergy, you can observe the appearance of symptoms in a couple of minutes up to 2 hours, and the reaction will last a couple of hours or less.

Given there is a freeing of antibodies in the blood circulation when there is an allergy, we can diagnose more severe allergies, called IgE-mediated, by a blood test, a skin test (Pick test or with a stamp) and also with an oral provocation test. For the oral provocation test, it is usually done in the hospital supervised by a medical team in order to react quickly after the allergen food is ingested and document the reaction of the child in a controlled setting.

When we talk about serious allergies to a food with an anaphylactic type response (immediate hypersensitivity), the reaction can be almost automatic, within the minutes or two hours that normally follow the ingestion and sometimes contact with the food. The evolution remains unpredictable. The reactions can be gastro-intestinal, mouth, respiratory tract, cardiovascular system, central nervous system, eyes and skin in 80-90% of cases. They can be very severe and place the child’s life in danger. Avoidance and an epinephrine self-injector are the treatments based on the child’s age.

Food intolerance

Intolerance (also called IgE-non-mediated type allergy or without medication) leads to discomfort or gastro-intestinal symptoms and occur after the ingestion of certain foods with variable intensity (discomfort, diarrhea, constipation, irritability, mucus). These reactions are increasing in babies and remain irritating as there are no tests to diagnose an intolerance. Most of the time, digestive symptoms that lead us to this conclusion, even if the skin and respiratory system can also be affected. For very young children, intolerance to cow milk proteins is without a doubt the most frequent as it is the first foreign protein introduced to the newborn’s diet.

An intolerance does not provoke the baby’s immune system like a severe allergy, and there is no anaphylactic shock. But the intolerance can provoke an inflammatory reaction in the intestines within hours or days follow exposure and also lead to discomfort in the baby.

An intolerance can sometimes affect only the large intestine (distal colon), a situation that often occurs in the first 4 to 6 weeks of a baby’s life. This is considered the least severe form of intolerance. In a certain number of children, intolerance will continue to progress towards the small intestine, and in the worst case, affect the entire digestive system, from the esophagus to the anus. In the case of intolerance, the baby has no growth problems, gains weight adequately and is generally healthy.

The intolerance cannot be detected in blood or by skin tests as there are no antibodies circulating due to a case of an intolerance. This is why we would try to find the food that seems to create the undesired reactions in the baby a try to eliminate it from the breastfeeding mother with an elimination or exclusion diet. If the baby drink commercial formulas, you have to adjust the formula with proteins partially or strongly hydrolysed to help the baby digest and absorb. After 2-4 weeks will we see if the situation seems to improve or not for the baby. For a breastfeeding mother, it is useless to remove too many things at a time and deprive the mother of foods that do not affect the baby. For the baby, start by eliminating milk given that milk proteins are the most frequent allergen, then, if only necessary, soya then beef. Next, we’ll eliminate soy (if necessary), then eggs, and if necessary (in very rare cases) we’ll remove wheat, corn and beef.

If the baby’s reaction to cow milk protein is rather slight (discomfort is present, without other major symptoms), the simple fact of diminishing daily milk sources in the breastfeeding mother will improve the situation, above all if the mother consumes too many portions of dairy products in a day (recommended 3-4).

If the baby’s reaction to cow milk proteins is rather severe (vomiting, blood in stools, severe diarrhea, dermatitis, breathing difficulties or generalized urticaria), the exclusion diet for the mother will be stricter and requires the elimination of all sources of milk, even trace, in many products sold and consumed in our everyday diet – cereal, bread, soup, sauces, candy, vinaigrettes, etc.

You should almost always start by removing all sources of cow milk protein (milk, cream, cheese, yogurt), because it is the most extensive allergen in Canada. If you do not note a change, you have to examine what other food could cause reactions in the baby and eliminate it for at least 7-10 days because normally it takes 3-6 days to completely remove the cow milk proteins from breastmilk.

To gradually reintroduce traces of bovine protein via dairy products into the diet of a breast-feeding mother who has been on the avoidance diet for at least 3 months, ideally you should wait until the baby is over 6 months old before attempting to reintroduce the allergen, and then only if there have been no significant symptoms for 3 weeks. If symptoms recur, wait another 3 to 4 weeks before attempting to reintroduce the food (12 months if the baby is very fragile or born prematurely).

It is never advisable to restrict the diet of a new breast-feeding mother as a preventive measure, even if there is a history of intolerances or allergies among siblings.  Avoiding food puts the child at even greater risk over time.

Here’s a useful tool for all moms on an eviction diet, made by Allergie Québec (in french only).

In Canada, we often noted crossed allergies, like goat and sheep milk at 90%, soya 10-15%, beef 10% and other rarer allergies, such as oats, eggs and other grains (barley, corn and wheat), a vegetable (ex.: avocado), other meats and fish are other possible allergens, in order of importance. In Australia, rice is the larges allergen, and in the US soya.

In the case of more serious reactions, it is often advised to see a nutritionist that specialises in pediatrics, or even an allergist if needed.

Food journal

It is a good idea to keep a food journal to follow up with a nutritionist, doctor or allergist. If a baby reacts to an allergen, they could be more likely to react to other sources of nutrients with an allergen potential, like a different cereal for example (other grain, reaction).

This is why when we introduce solid foods for a baby that shows intolerance or allergies in the first months of like, we suggest slowly introducing new foods while not delaying them. You should start with vegetables and fruits that have a lower risk of reaction, and then add meats (never before 6 months of age) and cereals later. It is good to follow up with a nutritionist to see changes in the situation, a follow up for the growth of your baby over time with the addition of foods and their reactions. Parents need to be guided to know when to reintroduce milk proteins in the baby’s diet, and that can easily be around 9-12 months.

At the start, when the baby’s reaction to an allergen is slight and the baby’s condition has really improved with an elimination diet for the breastfeeding mother, try later, after the baby reaches six months, and reintroduce the food allergen in the mother’s diet (like traces of milk protein). You will try to note if the baby’s reactions reappear or not.

This is like an oral provocation. We note if the child, despite the fact that their digestive tube as matured at around 9 months, remains fragile vis-à-vis the cow milk protein. If the reaction returns, the food is stopped again and the allergen can be reintroduced after the baby has been symptom-free for 3 weeks. If the baby’s reaction was severe, wait until after 1 year of age or even more depending on the case, with directions from an allergist. We will go very gradually. On the scale of reintroducing milk proteins, you can start with traces of milk in a cooked recipe, such as muffins or cookies. Next, a recipe with more milk, such as in pancakes or omelet, and gradually, if the breastfed baby is still symptom-free, we can move on to cheese on pizza and finish with milk to drink or with a portion of yogurt, ice cream or cheese.

When certain foods and allergens are introduced, a child may react more intensely and develop enterocolitis syndrome. This is induced by food proteins, also known as SEIPA. In fact, this syndrome refers to an inflammation of the mucous membrane of the small and large intestine (the colon), and when the system reacts to a food, in this case, it’s a reaction of the child’s immune system. In this syndrome, vomiting and/or diarrhea often occur 2 to 3 hours after ingestion of the food concerned and can lead to severe dehydration and complications for the child. Dairy products and soy are the two allergens most associated with SEIPA. Sporadic follow-up with an allergist and nutritionist is advisable, and in most children, the syndrome resolves spontaneously before school age.

For babies that receive commercial formula and react to it, you have to document their medical history and then see if a milk that is easier to digest can be suggested if necessary.

5% of newborns manifest allergic reactions compared to 3-4% of adults. A high number of food allergies diagnosed before 3 years of age will disappear over time.

Origins of Food Allergies

Most often food allergies result from combinations of genetics and environment (family medical history). If the two parents have allergies, the child has a 40–60% chance of developing them. If one parent has allergies, 20–40% chance. Finally, if the parents don’t have allergies, the child has a 5–10% chance.

Babies have a higher risk of developing food allergies when their parents, brothers or sisters:

• Have episodes of severe eczema with persistent patches;
• Have already been diagnosed with food allergies;
• Or have been diagnosed as asthmatic or suffer from seasonal allergies like hay fever.

This shows predisposition, family history of reactions to potential allergens. The foods with the highest level of allergens in children are:

• Products containing cow milk proteins;
• Soy;
• Eggs.

Wheat, corn and beef come next. Peanuts, nuts and fish & seafood follow, at smaller scales of sensitivity.

Research studying food allergies indicates no consensus about cross-reactivity often noted with cow milk protein, bovine protein (beef) and soya. Considering family history, when an allergic child is already present, you need to act on symptoms faster for another baby from the same parents.

As mentioned earlier in this post, however, it is not recommended (2023 update) to restrict the diet of a mother breastfeeding her new baby, even if there is a history of allergy or intolerance in the family. Restricting or delaying a newborn’s exposure to certain food in the breast milk could ultimately put it at greater risk of developing allergies, despite good intentions.

Besides the hereditary aspect, a baby can have an immature intestine with inadequate or excessive defences against proteins normally inoffensive for most people. This can explain an allergy occurring with early exposure to certain allergens before six months of age. The “allergen” protein makes the immune system react, and the body goes on the defensive producing antibodies (chemical substances) that circulate in the blood. This produces different clinical signs and symptoms.

Signs of a Food Allergy

The symptoms of a food allergy can vary from one child to another and in intensity. When a baby is in contact with an allergen, they will react by producing antibodies and could present the following signs:

• Rashes on their body;
• Eczema or urticaria;
• Skin swelling (ex.: swollen eyes, bloated face, swollen lips);
• Constant congestion or nasal dripping, even if their general condition is fine and they don’t have an infection;
• Eyes water or itch;
• Fast, shallow breathing. To be supervised as the immune system reaction can affect the respiratory tract and cause severe and dangerous respiratory difficulties.

In babies, two hours after ingesting the food, you might see:

• Vomiting either instantaneously or within a couple of hours after ingesting the allergen;
• Cramps and diarrhea (not to be mixed up with an exclusively breastfed baby’s stool which is often runnier);
• Sometimes persistent constipation (with or without anal fissure);
• Blood (or mucus) in their stool (unless they have an anal fissure);
• Systematically cries each time they’re exposed to the allergen.

It’s important to note that even if a baby’s stools contain mucus or a small amount of blood on a very temporary basis, this does not automatically mean that the baby has a food intolerance or allergy. However, if these signs persist for more than 4 weeks, medical investigation is required. It’s important to always look at the baby’s general condition, which tells us a lot about his or her state of health before concluding whether or not a child has a food intolerance or allergy.

When should you be worried?

• When swelling affects the face, mouth, tongue, lips;
• When the general health of your baby declines;
• When there is weight loss or a slowing of the growth curve;
• When the baby suddenly vomits;
• When the baby has difficulty breathing;
• When their voice changes, becomes a bit husky;
• When their lips or face become paler or bluish;
• If the baby is weak or faints.

In these cases, call 911 immediately.

What to do after an allergic reaction?

What should you do when dealing with an allergic reaction?

• Continue breastfeeding (eliminating dairy products, then soy (and then eggs if necessary) at intervals of 2-3 weeks between them, to see if there’s a noticeable change in the baby. Then, in rare, more serious cases, remove wheat, corn and beef last.. The rest of the diet remains varied;
• A breastfeeding mother starting an elimination diet for dairy products needs a dietary supplement of 1000 mg calcium/day and 400 UI vitamin D to compensate for their dietary restrictions;
• You shouldn’t delay introducing solid food for babies that have already shown intolerance or allergy signs. At 4–6 months, babies can eat cereals, fruits and vegetables if required. At six months, you need to start solids for all babies for their iron intake (meat, enriched cereals) required for their growth;
• Don’t give them foods that seem to provoke an allergic reaction but give them others. You shouldn’t stop feeding them solid foods if the baby is over six months of age;
• Don’t delay introducing other nutrients considered as potential allergens, such as fish, nuts or eggs. Scientifically speaking, it’s not beneficial to delay the introduction of foods for the prevention of allergies (British Columbia, Health Line BC, 2013). According to the latest December 2022 data from the Canadian Society of Allergy and Clinical Immunology, peanuts and eggs are the top two allergens to give a baby after 6 months of life;
• If the baby drinks formula and shows signs of allergies, see a doctor before changing. You can be prescribed hypoallergenic (or strongly hydrolysed) formula preventing skin reactions such as eczema or asthma. This special formula digests easier than more traditional cow milk or soya milk and can help delay or diminish symptoms. Sometimes you can use soy milk, but always after six months;
• For severe allergies, the doctor or allergist can prescribe formulas made with amino acids;
• Returning the allergen food in the diet after a severe reaction by the child (milk, bovine, soy or other proteins) depends on each child, the allergen in question, their entire history and the response they had. Only your doctor or allergist can tell you when to reintroduce it. Sometimes, it will be after one year of age and sometimes even 2–3 years, when the child will be able to indicate their discomfort. Some children will eat in a secure environment with the specialist and their team, ready to react in case of strong reactions;
• The use of probiotics (Lactobacillus reuteri) is being studied to help babies calm their crying, especially when breastfeeding. Today, we still don’t understand how probiotics function, but the results seem to show an improvement in their crying and help their immature intestine build the intestinal barrier (intestinal microbiota);
• Attention: Soya, rice or almond drinks aren’t good alternatives for sensitive newborns. Additionally, you should avoid goat or ewe milk, because the protein resembles that of cow milk. So not before 12 months.

Here is an interesting link from the Canadian Society of Allergy and Clinical Immunology to a handy document for you parents.

It’s not easy to diagnose an allergy in a very young child. Your observations of your baby can play an essential role in helping health professionals build their history and collect data needed to understand the problem to advise you.

Please keep an eye out for signs of allergies, especially if you have them in the family. Importantly, before changing your baby’s diet, consult people who can guide you. Don’t forget that these changes may lead to more undesirable reactions in your baby.

For more information on the subject, visit the Allergies Québec website at the following link: https://allergies-alimentaires.org/en/.

For more information, please watch the live video Milk Intolerance and Allergy where we respond to parents’ questions and concerns.

Finally, you can print the Guide to Introducing Solid Foods to an Infant (in french), where you can check off foods as you introduce them to your baby. You can also consult the Pediatric Nutritionists website which offers an introduction table of allergens with lots of very interesting tips.

Talk soon,

Marie Fortier
The Baby Expert

Updated article : April, 2024.