Milk Intolerance In Babies

Milk Intolerance In Babies

Milk Intolerance In Babies

If your baby is gassy, cranky, and passes loose stools, you might worry that he is not tolerating his baby formula, or reacting to something in you have eaten. Find out what the symptoms of intolerance are, foods and food chemicals that cause intolerance, and how to manage this problem.

What is an intolerance?

Food intolerance is a digestive system response rather than an immune system response (as is the case for food allergies). Gastro-intestinal (GI) symptoms develop as a reaction to something within a food that a person is unable to properly digest due to an enzyme deficiency, or unable to absorb, or which irritates the stomach or intestinal tract.

Food intolerance is a ‘dose-related’ condition. Reactions vary in intensity depending on the amount of the food consumed. Symptoms don’t usually occur until a certain amount (threshold) of the food is eaten. The amount varies between individuals.

Signs and symptoms of milk intolerance 

Symptoms are usually confined to the gastro-intestinal (GI) tract.

Physical signs:

  • diarrhea is the most common sign;
  • constipation in some cases;
  • bloating;
  • extreme flatus;
  • poor growth - depending on the frequency of exposure.

Behavioral symptoms:

  • irritability;
  • sleep disturbance;
  • feeding refusal.

Symptoms can be delayed for up to 12 to 24 hours after exposure to the problematic food.

These signs and symptoms can also occur for many other reasons. So it’s important to have your baby seen by a doctor.


Foods that cause intolerance 

Milk is the most common source of food intolerance. But other foods can also cause symptoms linked to intolerance.

Food is composed of protein, carbohydrate, fat and various nutrients as well as a number of natural chemicals. Reactions can occur to any of these components.


The incidence of milk protein intolerance is much higher for formula-fed babies compared to breastfed babies. There are many different kinds of food proteins. The type of proteins in milk varies between species. All baby formulas, other than highly specialized hypoallergenic formulas, are based on cows’ or goats’ milk or soy protein. The protein and other nutrients in cows’ and goats’ milk and soybeans are “humanized” to make baby formulas more like breastmilk. However, it’s not possible to replicate the nutrients of milk produced by humans. Some babies have trouble digesting the proteins from other species or plants such as soy.

Note: In regards to breastfed babies, there is an abundance of myths and misconceptions linking babies’ GI symptoms and irritability to their mothers’ consumption of milk proteins and other foods. The likelihood of a breastfeeding mother’s diet being responsible for her baby’s symptoms of intolerance is very low. GI symptoms and distress experienced by exclusively breastfed babies is infinitely more likely to due to lactose overload as a result of oversupply syndrome.


Carbohydrates such as lactose, fructose, sorbitol and others can cause food intolerance.

The milk of all mammals, i.e. humans, cows, goats and others, contains lactose. While it's extremely rare for babies to suffer from lactose intolerance, except temporarily during and following gastroenteritis, lactose overload is a common cause of GI symptoms displayed by healthy, thriving babies during the early months of life. (See Lactose overload for reasons.) 

Its for the very reason that fructose (found in fruits) and sorbitol (found in prunes) are often poorly digested by babies, and thus have the potential to cause diarrhea, is why fruit and prune juice is often recommended as a treatment for constipation. (See Carbohydrate intolerance for more)


Some babies with rare metabolic disorders are not able to adequately absorb the fat in regular infant formulas and require specialized formula. 

Other foods

Cheese, yogurt, chocolate, egg, wheat and other grains that contain gluten, flavor enhancers, food additives and natural salicylates found in strawberries, citrus fruits and tomatoes are also linked to food intolerance.

Who is at risk of intolerance?

Babies, children and adults can be troubled by food intolerances. Babies are particularly vulnerable due to immaturity of their digestive systems. Immaturity can limit a baby’s ability to produce sufficient quantities of particular dietary enzymes to match the type or amount of food consumed. Whether a baby reacts or not, can depend on the type and amount of food he is given. Babies’ threshold is much lower compared to adults.

The percentage of babies affected by milk intolerance is unknown. Some experts estimate that up to 8 percent of babies and children could be intolerant to one or more foods. Others believe the figure could be higher.

Diagnosis and treatment of milk intolerance in babies

Present day tests are of little benefit in the diagnosis of milk protein intolerance. Generally, there are no physical signs observable by health professionals. Diagnosis is usually based on the parents’ description of physical signs (diarrhea, gassiness etc.), baby’s behavior, and baby’s response to treatment.

Formula-fed babies

Diagnosis is complicated by the fact that the same GI symptoms occur in the case of lactose overload, cows’ milk protein intolerance and secondary lactose intolerance following a gastro-intestinal infection, and other causes. 

Treatment typically involves a “let’s try this and see” process. The first step is to switch baby to a hypoallergenic formula(which are lactose-free and contain proteins that are already broken down) or soy infant formula (which contain no cows’ milk proteins and are lactose-free). Because around 50 percent of babies who react to cows’ milk proteins will also react to soy proteins, most babies suspected of cows’ milk protein allergy or intolerance are switched to a hypoallergenic formula.

Note:  The diagnosis of protein intolerance is often believed to be confirmed if baby’s GI symptoms disappear after switching to a soy or hypoallergenic formula. However, these formulas will also relieve symptoms due to lactose overload, which occurs as a result of overfeeding. (Lactose overload problems experienced by formula-fed babies can generally be resolved through appropriate feeding management and seldom requires dietary change).

Breast-fed babies

Diagnosis of milk protein intolerance in a breastfed infant can be a complicated process because a baby could react to more than one food eaten by the mother. 

Treatment begins with eliminating milk and dairy from the mother’s diet. If this fails to improve the situation, she might then be advised to restrict soy and a number of other foods.

Note: If the cause of baby’s GI symptoms is due to lactose overload and not milk protein intolerance, maternal dietary restrictions will make no difference. Lactose in breastmilk is not influenced by maternal diet. Lactose will be present in breastmilk irrespective of whether the mother consumes milk and dairy or not.


Through a thorough history of the onset of symptoms, baby’s, and a breastfeeding mother’s diets, medications taken by each, and by exploring parent’s infant feeding and settling practices, the cause of baby’s GI symptoms and/or distress can usually be identified. However, this process is time consuming and most health professionals are not trained to advise parents on infant feeding and sleeping management, and so it's typically assumed the cause of a baby’s distress is physical.

There is of course, a small percentage of babies who experience digestive and growth problems as a result of cows’ milk protein intolerance. However, based on my experience, many irritable newborn babies are misdiagnosed with milk protein intolerance by parents and health professionals simply because they are unaware of lactose overload and behavioral reasons for infant distress. If your baby has GI symptoms, rule out lactose overload, first.

I also often see healthy, thriving babies diagnosed with cow’s milk protein intolerance despite having no GI signs that point to a food intolerance. A diagnosis made based on the fact that baby often cries, has trouble sleeping, or because he/she fusses or reject feeds. Usually the diagnosis of milk protein allergy or intolerance in this situation is part of the “let’s see if this helps” process after medications to treat colic and/or reflux have proven unsuccessful. If there are no physical signs of intolerance, then intolerance is unlikely to be the cause. (See our articles on crying, over-tiredness, bottle-feeding problems and feeding aversion.)

Consequence of misdiagnosis 

Formula fed babies

A misdiagnosis in the case of a formula-fed baby is not a big change in regards to an effect on his health. He was already receiving formula, but now receives hypoallergenic formula instead. He might not like the bitter taste of hypoallergenic formula to start with, but if that’s all he’s offered he will drink it. Rejection might occur after he starts eating solids, and discovers other foods taste much better than his formula.

Parents could be financial disadvantaged if they have to pay full price for hypoallergenic formula, which costs around 3 times as much as regular infant formula. Some national and private health schemes subside the cost of hypoallergenic formula for parents. 

Breastfed babies

Misdiagnosis provides a greater disservice to breastfeeding mothers and their babies. Once headed down the path of maternal dietary restrictions, if baby’s situation does not improve, it's tempting for a mother to make further and further dietary restrictions. Some breastfeeding mothers survive on severely restricted diets, which over time negatively impacts on their health. If their health is adversely affected by dietary restrictions, many mothers feel they have no option other than to cease breastfeeding and switch their baby to hypoallergenic formula. Baby and mother are then deprived of the benefits associated with breastfeeding. Many mothers grieve as a result of not achieving their breastfeeding goals.

It would be a real shame if any mother is erroneously advised or decides to restrict her diet, and for any baby to be switched from breastfeeding to hypoallergenic formula, if the cause of baby’s symptoms is not due to foods eaten by the mother. It happens, all too often!

Written by Rowena Bennett

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