Milk Allergy versus Milk Intolerance

Created: December 15, 2015. - Reviewed: January 24, 2016.

If baby is often irritable, and also displays signs of tummy toubles, milk allergy and intolerance is often suspected as the cause. Breastfeeding mothers restrict their diets and formula-fed babies' formula is switch... often multiple times.  Understanding the difference between allergy and intolerance could spare your baby from a trial and error process as you try to pinpoint the cause. 

Milk Allergy versus Milk Intolerance
Rowena Bennett

Rowena Bennett

  • Registered Nurse
  • Registered Midwife
  • Child Health Nurse
  • Mental Health Nurse

Rowena over 20 years experience assisting parents to resolve well baby care problems.


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Allergy or intolerance?


There are several digestive disorders related to milk. The most common include:


  • Lactose overload
  • Lactose intolerance
  • Cow's milk protein intolerance (CMPI)
  • Milk and soy protein intolerance (MSPI)
  • Cow’s milk protein allergy (CMPA)


The terms ‘allergy’ and ‘intolerance’ are often used interchangeably, but they not the same. The cause and treatment differs.


It can be difficult to tell these disorders apart because some physical signs will be the same for all of these disorders, as are behavioral symptoms such as irritability and wakefulness.  However, there are usually signs that vary.


Lactose overload (also called transient lactase insufficiency) is a feeding management problem and not a digestive disorder.  The reason for inclusion in this article is because the GI symptoms linked to lactose overload are often mistakenly attributed to digestive disorders such as lactose intolerance and milk protein allergy or milk protein intolerance (and also colic and reflux).





                  TYPICAL SIGNS OF


Lactose overload


A normal body response to excessive amounts of lactose due to oversupply of breastmilk or overfeeding via bottle.

Breastfed: 2/3 of all breastfed babies during the first 3 months.

Formula-fed: Unknown.

Incidence is highest in first 3 months due to active sucking reflux, which increases risk of overfeeding.


· Breastfed babies: Frequent watery, explosive bowel motions.

· Formula-fed babies: Sloppy, foul-smelling stools.

· Extreme flatus. (Farting)

· Average to above average growth.

·  Mucous and blood in stools in prolonged and severe cases.

·  Milk regurgitation (reflux) may or may not be visible.  Extreme reflux may be linked to overfeeding, which in turn causes symptoms of lactose overload.

· See lactose overload for more signs and symptoms.


Feeding management.

Lactose intolerance


Due to low levels of lactase (the digestive enzyme needed to break down lactose).

Primary lactose intolerance at birth is extremely rare.

Secondary lactose intolerance following gastro-intestinal infection, unknown incidence.

· Frequent diarrhea.

· Weak, lethargic baby.

· Poor growth

· Lactose intolerance does not cause vomiting, however, vomiting or reflux can occur for other reasons.

Continued breastfeeding


lactose-free formula.


Milk or soy protein intolerance


Due to inability to adequately digest (break down) the problematic food protein.

Breastfed: Unknown. Incidence significantly lower compared to formula feeding due to protein type. 

Formula-fed: 1:10 suspected of food intolerance. This figure includes all forms of food intolerance, lactose and protein from milk and food.

· Diarrhea

· Poor growth

· Protein intolerance does not cause vomiting, however, vomiting or reflux can occur for other reasons. See Milk protein intolerance for more.

Maternal dietary restrictions


infant formula based on an different protein source or

hypoallergenic formula.

Milk protein allergy


An abnormal immune system response to rid the body of harmless a protein allergen.

Breastfed: 1:250

 Formula-fed: 1:50

Increased risk for babies with family history of allergies.

· Vomiting

· Diarrhea

· Mucous and/or blood in stools

· Rash or eczema

· Coughing, sneezing, wheezing and/or breathing difficulties

· Poor growth

· See Milk allergy for other signs and symptoms.

Maternal dietary restrictions


hypoallergenic formula. 

Breastfed babies


While it is possible for a breastfed baby to have an allergic reaction or experience intolerance to cows’ milk protein or other food proteins eaten by his mother and transferred into her milk, the risk is significantly lower compared to formula-fed babies who receive cows’ or goats' milk-based infant formula and other food proteins such as soy directly.  The protein in breastmilk is softer, more easily digestible compared to proteins used in the production of infant formula.  Breastmilk also contains digestive enzymes that help a baby to digest the protein within breastmilk.


Consider how milk or food proteins might enter breastmilk.  Protein eaten by the mother is broken down into protein molecules in her stomach and digestive tract before it is absorbed to her blood stream.  [If food proteins are not broken down into smaller protein molecules in the digestive tract, they are usually too large to be absorbed in the blood stream, and will be passed through the mother’s digestive tract.  An exception may be if the mother has ‘leaky gut’.]  Nutrients in the mother’s blood stream are first filtered by her liver and then face a further filtration system within the mother’s breasts.  This complex and highly sophisticated biological process produces milk with a low risk of containing allergens and even lower risk of containing food proteins linked to intolerance.


Note: Around 2/3 of healthy breastfed babies under the age of 3 months at some point experience gastro-intestinal symptoms linked to lactose overload.  The amount of lactose in a mother's milk is not affected by dietary restrictions.  Whether she drinks milk or eats dairy food or not, the amount of lactose in her milk will be the same. 

Get the diagnosis right


Present day diagnostic tests are unreliable when testing babies for allergy or intolerance.  Lactose intolerance tests will give false positive results for lactose overload.  Diagnostic tests for allergies are usually inconclusive for babies under the age of 12 months and for certain types of allergies.


Without the aid of reliable diagnostic tests, diagnosis is based on physical signs observed by doctor and parent, and the parent’s description of their baby’s behavior.  Hence, a diagnosis depends on what a parent or health professional thinks is the most likely cause based on their knowledge and experience.


A diagnosis is believed to be confirmed when physical signs and behavioral symptoms resolve following treatment.  Ideally, there will be elimination process to pinpoint the exact cause so that the baby and/or breastfeeding mother do not face unnecessary dietary restrictions.  However, in some cases the first line of treatment used by medicos is to switch baby to a hypoallergenic infant formula.  Hypoallergenic formulas, which are also lactose-free, will resolve GI symptoms associated with all of the above disorders including lactose overload.  While bypassing an elimination process, switching to hypoallergenic formula as the first step does not provide the benefits of identifying the actual cause.  It may even provide a disservice to baby and mother if breastfeeding needlessly ends.


It’s sometimes assumed that a baby is intolerant to lactose or cow’s milk protein if symptoms resolve after switching baby to a soy-based infant formula.  But soy infant formula is also lactose-free and as such will relieve GI symptoms associated with lactose overload.


NOTE:  Maternal dietary restrictions do not resolve GI symptoms linked to lactose overload.  The lactose content in breast milk is not influenced by maternal diet or dietary restrictions.


GI symptoms present

Lactose overload is the most common of all problems affecting the digestive tract of newborn babies.  This problem is distinguishable from the digestive disorders listed by the fact that baby is gaining weight, something that does not occur prior to milk allergy or a digestive disorder being effectively treated.


If your baby is thriving and physical signs relate primarily to her GI tract, (i.e. there are no signs such rashes, and breathing difficulties pointing to an allergy) you may find it beneficial to rule out the possibility of lactose overload before assuming her troubles are due to a milk allergy or intolerance.


GI symptoms absent

I often see babies who were diagnosed with milk allergy or intolerance despite the absence of physical signs that point to these conditions.  Breastfeeding mothers are advised to restrict their diets or cease breastfeeding and babies are switched to a hypoallergenic formula in the vague hope that this might resolve distressed behavior such as persistent crying, sleep disturbance, milk regurgitation or aversive feeding behavior.  A diagnosis of milk allergy or intolerance commonly occurs after medications to treat colic or acid reflux fail to resolve a baby’s troubled behavior.


In the case where there are no GI signs pointing to allergy or digestive disorder, dietary restriction or change is unlikely to improve the situation, and in fact may cause further deterioration of the status quo due to the unpleasant taste of hypoallergenic formula or as a result of ceasing breastfeeding.


See Why Others Fail to identify lactose overload and other behavioral feeding and sleeping problems commonly experienced by healthy babies.  [‘Behavioral problem’ implies a baby’s troubled behavior occurs in response to the circumstances, i.e. feeding and settling management.]


Written by Rowena Bennett

© Copyright 2004. All rights reserved. Permission from author must be obtained to copy or reproduce any part of this article.

How we can help!


To avoid stress and complications occurring as a result of what could potentially be needless dietary restrictions or changes, you need to be sure a diagnosis of milk allergy or intolerance is correct.


Bear in mind that a confirmed diagnosis and effective treatment does not guarantee your baby’s contentment.  Your baby, like other non-affected babies, can still experience behavioral feeding or sleeping problems, the most common of all reasons for infant irritability and sleep disturbance.


We can assist you to identify and effectively manage a lactose overload problem, as well as other causes of infant distress, broken sleep and feeding issues, potentially without the need for baby or maternal dietary restrictions.  (We won’t know if dietary restrictions are necessary until we have reviewed your baby’s case).  See consultation service for more.


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