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What is the Connection Between Breastfeeding and Allergies?

Breastmilk has a plethora of immunological effects to give your baby the best start in life. It contains stem cells, antibodies to help your baby fight viruses or bacteria and 415 proteins! It is also a great way to build a connection with your baby through skin-to-skin contact.

Recent studies suggest there are links between allergies and breastfeeding. It is unusual for your baby to be allergic to your breastmilk itself. However, after you have eaten particular foods, you may witness specific indicators (which we will discuss later) in your baby.

This blog post is intended to inform you of the relationship between breastfeeding and allergies, the signs to look for and how to avoid them!

A mother hugging a crying baby
Food allergies can be a distressing experience for both the baby and the parents.

How Does Breastfeeding Cause Allergies?

First of all, an intolerance means that the baby cannot digest a specific food. This usually causes problems like tummy ache, diarrhoea, bloating or headache. It can be pretty unpleasant, but it’s not life-threatening.

An allergy is much more severe because it involves a response of the immune system (our body's defence system) against a specific food. Usually, food is not recognized as a threat by our system. Still, some particles (called allergens) in the food can elicit an improper production of antibodies and a cascade of effects which can go from a mild rash on the skin, to more serious problems like a swelling in the throat (which can potentially cause suffocation) or to an anaphylactic shock which require immediate medical attention.

Babies can develop allergy or intolerance to some specific food in the same way as an adult can do. Between 4 and 6% of children might have some sort of intolerance or allergy. Most of the time, the problem becomes evident when the baby is weaned and comes in direct contact with the food and only 0,04 – 0,5% of babies show allergy when exclusively breastfeeding. So, the overall chance that your baby might be allergic to something present in the breastmilk is quite low.

In general, breastfeeding seems to protect against allergies or intolerances. This is still a quite debated point in the scientific community, but data are showing that babies exclusively breastfed are less common to show the problem than baby fed on formula milk. This is because formula milk is based on cow’s milk proteins which could trigger the reaction. That’s another good reason to breastfeed exclusively your baby for the first 6 months of life.

Another interesting thing about allergies in babies is that it has a genetic background. It’s indeed more common for a baby to have the problem if one or both the parents or a sibling have a history of allergy or intolerance to some food. So, just by looking at the direct family, it’s possible to say if a baby is at a higher risk of developing allergies.

But how does it work? How is it possible to have this problem with breastmilk?

The food a mother eats is processed into the stomach, and the gut digests it and decomposes it into nutrients that are then absorbed into the bloodstream. Usually, small nutrients cannot cause any reaction in the system. However, big food particles can be absorbed into the bloodstream. For instance, in the case of cow’s milk protein intolerance, big proteins pass into the mother system. From the bloodstream, they pass into the breastmilk and finally into the baby’s system to cause an allergic reaction or intolerance.

Most Common Food Allergies

The most common cause of an allergy to food is cow’s milk. Other foods like fish/seafood, soy, egg, peanut or tree nuts, fruits and grains are all prevalent allergens. Other foods commonly eaten by breastfeeding mothers, such as citrus fruits, additives and artificial colourings, are more likely involved in either irritation or intolerance.

Signs of Intolerance

Allergies/intolerances can cause several visible signs. Keep your eye out for the following:

  • A rash that is red and itchy

  • Eyes, lips, and face may swell

  • Vomiting, stomach ache, diarrhoea, colic or constipation

  • Blocked or runny nose

  • Eczema that will not respond to treatment


If your baby exhibits any of the previously mentioned indicators of an intolerance or allergy and they are exclusively drinking breast milk, they are likely intolerant to something you are eating.

One way to establish the problematic food is by following an elimination diet. An exclusion or elimination diet attempts to exclude suspect foods from a person's diet that are triggering an allergic reaction. It may be difficult to fully remove foods because they can appear as an unexpected ingredient in processed or baked foods. Cow's milk products, for example, can be used in dairy products and in a variety of other foods. Unfamiliar names are often used to mask the food object.

To relieve their babies' symptoms, mothers can try removing one allergen at a time to discern if there is any change, or they can adopt a low allergen diet. The benefit of the elimination diet is that it can be used to diagnose the problem and as a cure!

Intolerance should be diagnosed by your doctor and can also be confirmed by a blood test to confirm the presence of a natural immune response against the particular food.

But what if the elimination diet is done just for the sake of preventing the possible allergy? You might wonder if it would be worth doing an elimination diet even if you are not sure if your baby is intolerant to some specific food, especially if in the family there is somebody else already allergic. The problem is that elimination diets are difficult to stick to and are advised to be done under the guidance of a dietitian to maintain the mother's health. It’s indeed important to supplement your diet with calcium (1,5g a day) and a multivitamin if you are following this elimination diet. The bottom line is that an elimination diet is something that mothers should do only under medical advice and after a careful assessment of the specific case to weigh risks and benefits.

The same thing applies to pregnancy when an elimination diet could avoid allergies in the baby later on in life. This approach does not seem to be advisable because the benefits are not much compared to the risk of weakening the mother’s health if essential food like dairy and eggs are removed from the diet. Some guidelines do advise though the exclusion of peanuts especially at the end of pregnancy because this food is not necessary, and it could potentially lead to allergy.

Lactose Intolerance

Lactose intolerance is a condition in which the body is unable to absorb lactose. Since breast milk is high in lactose, and babies are normally well equipped to digest it, true lactose intolerance in babies is extremely rare. Lactose intolerance may be inherited as a result of a metabolic disorder (a rare but severe health risk) or acquired as a temporary condition due to a variety of factors.

Is being intolerant to lactose the same as being allergic to cow’s milk?

Lactose intolerance or lactose overload is not the same as having a reaction to traces of cow's milk protein that enter breast milk from the mother's diet. However, a long-term food allergy may harm the lining of the stomach, which produces the enzyme required to digest lactose, resulting in lactose overload symptoms.

Lactose overload and cows' milk allergy can also occur simultaneously. Since lactose is added to breast milk in the breast, removing lactose from a mother's diet would not improve a baby's lactose overload symptoms. If the main problem is a reaction to cow's milk protein, eliminating lactose-containing foods would likely alleviate the symptoms because cow's milk proteins and lactose are commonly contained in the same foods.

How to Treat a Milk Allergy

Many children outgrow milk allergies by the age of one, and most babies who have milk allergies outgrow these by the age of three.

As it’s mentioned earlier, the elimination diet is both important to establish the cause of the problem and to fix it. An elimination diet done approximately 2 to 4 weeks should be enough to see the issue disappear, and if this is the case the mother has to stick to the diet until the end of breastfeeding. If the elimination diet fails, then more test will be needed to understand what’s wrong.

In case it’s needed to supplement breastfeeding with formula, a hypoallergenic formula should be given to the baby. These formulas, also called Protein Hydrolysates, have been processed in a specific way to eliminate or reduce the substances causing the allergy.

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