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Milk Allergy, Milk Intolerance or Lactose Intolerance?

The terminology used for allergies and intolerances is frequently used interchangeably. The terms milk allergy, milk intolerance and lactose intolerance are often thought of as one and the same. But the truth is, they are three different conditions with different physiological processes. Subsequently, each condition requires a different testing method. Today we’re exploring exactly what those differences are, and how to tell them all apart.

The Difference Between the three conditions

Milk Allergy and Milk Intolerance

Food Allergies and intolerances are immune-mediated responses. This means that the reactions are caused by your body producing antibodies (AKA immunoglobin [1]) in response to a certain food’s proteins. This happens because the body has perceived the food item as a threat, and is sending those antibodies in, to ‘deal with’ the problem (the same way a mob boss would send his goons to ‘deal with’ a nuisance). 

The antibodies produced through a food allergy or intolerance are IgE and IgG, respectively [2]. You can test for these antibodies with blood sample testing. 

Lactose intolerance

Whilst a milk allergy and a milk intolerance are immune-mediated requiring blood allergy testing or intolerance testing, lactose intolerance is enzyme-mediated, meaning symptoms occur due to an insufficiency of the enzyme lactase [3]. In this case, a breath test checking for excess levels of methane and hydrogen is required.

Symptoms of each condition

Milk Allergy

Whilst all three conditions could result in symptoms which can be debilitating such as bloating, stomach cramps, vomiting and diarrhoea, only a milk allergy has the potential to be life-threatening[4]. For most people, allergies cause symptoms such as congestion, swelling, hives or vomiting, but for some, they can be as severe as an anaphylactic shock which can be fatal. If you suspect you or a family member has an allergy to milk, then allergy testing is highly recommended, particularly if you, or they, also have asthma.

Symptoms of a milk allergy can include;

  • Diarrhoea
  • Hives
  • Itchy, water eyes (often red)
  • Swelling of the lips, tongue, eyes, or face
  • Tight chest
  • Vomiting

Milk Intolerance

Milk intolerance is a condition associated with high levels of the antibody IgG and can, therefore, be identified through blood testing [5]. It can cause various digestion-related symptoms and do can often be confused with lactose intolerance. However, symptoms are not limited to the digestive tract, as nausea, headaches and even hives are common for those suffering from milk intolerance. 

Symptoms of milk intolerance can include;

  • Bloating
  • Constipation
  • Diarrhoea
  • Fatigue
  • Headaches or migraines
  • Nausea
  • Skin rashes and eczema

Lactose Intolerance

Lactose intolerance is an inability to break down the sugar, lactose, due to an insufficiency of the enzyme lactase. This inability causes the production of excess gases, hydrogen and methane, resulting in digestive discomfort. The levels of these gases can be tested through a breath test to identify the condition.

Symptoms of lactose intolerance can include;

  • Bloating
  • Diarrhoea
  • Excessive gas
  • Feeling sick
  • Stomach cramps or pains

Impact on Diet

The dietary implications of these conditions depend upon which one you have. With a milk allergy, it is recommended that you eliminate all milk products from your diet on an on-going basis. 

In the case of milk intolerance, your results may indicate that you are intolerant to certain milk products but not others, for example, milk but not cheddar cheese. This is due to the differing levels of proteins and bacteria in the various milk products. An initial period of elimination of 4 weeks is recommended, following this you may be able to successfully reintroduce the items however, this is highly individual. Many people choose to continue abstinence or reduce their intake of the intolerant milk products as they feel better for it. 

With lactose intolerance it is not always necessary to remove all milk products, this is because certain milk products, such as aged hard cheese, butter or probiotic-rich plain yoghurt have very little lactose in them, but this depends upon the severity of your lactose intolerance.

Telling them apart

The crucial differences in these conditions; milk allergy and milk intolerance are immune-mediated, producing antibodies that can then be tested for. Lactose intolerance is an insufficiency of the digestive enzyme lactase and can be tested for using a breath test. If you suspect your symptoms relate to a milk allergy or milk intolerance, convenient home to lab allergy and intolerance testing kits are available for you to quickly identify any existing conditions.


[1] Justiz, A.A. and Kamleshun Ramphul (2020). Immunoglobulin. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK513460/ [Accessed 5 Mar. 2020].

[2] Waserman, S., Bégin, P. and Watson, W. (2018). IgE-mediated food allergy. Allergy, Asthma & Clinical Immunology, [online] 14(S2). Available at: https://aacijournal.biomedcentral.com/articles/10.1186/s13223-018-0284-3 [Accessed 5 Mar. 2020].

[3] Malik, T.F. and Panuganti, K.K. (2019). Lactose Intolerance. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK532285/ [Accessed 6 Mar. 2020].

[4] Nih.gov. (2017). Allergies: Overview. [online] Available at: https://www.ncbi.nlm.nih.gov/books/NBK447112/ [Accessed 6 Mar. 2020].

[5] Lin, S., Yang, X., Xing, Y., Wang, X. and Li, Y. (2019). The Clinical Application Value of Multiple Combination Food Intolerance Testing. Iranian journal of public health, [online] 48(6), pp.1068–1073. Available at: https://www.ncbi.nlm.nih.gov/pubmed/31341848 [Accessed 5 Mar. 2020].