Cow’s Milk Allergy

Cow’s milk allergy can occur in anyone, including adults. However, it is a condition that more commonly affects the paediatric population. Diagnosis for cow’s milk allergy can be difficult and can often be confused with cow’s milk/ lactose intolerance. 

In this article, we’ll highlight the differences and similarities between milk allergies and milk intolerance, the underlying causes of a cow’s milk allergy, common questions that one may encounter, and practical ways to deal with cow’s milk allergy.

Is milk allergy and milk/lactose intolerance the same thing?

No, a milk allergy and milk/lactose intolerance are different. 

Milk allergy is an immune response to milk proteins. The body mistakenly identifies these proteins as harmful, producing specific antibodies against it. Upon repeated exposure to these proteins, the immune system triggers an exaggerated antibody response, leading to a cascade of chemical immune reactions, which manifest as signs and symptoms of milk allergy.

A lactose intolerance occurs due to the lack of the enzyme lactase, which is needed to digest lactose — a sugar found in milk. A milk protein intolerance is a non-allergic sensitivity to milk proteins, such as casein or whey. 

How can I differentiate milk allergy from milk/lactose intolerance?

In milk/lactose intolerance, one develops unpleasant gastrointestinal symptoms when they are unable to digest lactose effectively due to reduced amount of lactase.

The poorly digested lactose in the gut is subsequently being fermented by gut bacteria causing uncomfortable irritable-bowel-syndrome-like symptoms such as:

• Bloatedness
• Abdominal cramps
• Diarrhoea
• Constipation
• Nausea

Contrary to milk or lactose intolerance, an individual with a true milk allergy will not be able to tolerate any amount of milk, while in the case of lactose intolerance, one may still be able to tolerate a small amount of milk.

Types of milk allergy responses

Immediate IgE related

This type of allergy can occur very fast within seconds to minutes upon consumption of cow's milk. In IgE related allergy response, once the body is exposed to the 'allergen' protein, there will be an immediate trigger of a cascade of inflammatory allergic response and release of IgE antibodies, leading to an acute allergic reaction.

Delayed IgE related

This type of allergy tends to occur slower over a period of hours up to 3 days after consumption of cow’s milk. The immune response tends to develop progressively over time, and usually this is non-IgE related, immune response can often drag on with symptoms for days to even weeks. One commonly confused the symptoms of delayed response with milk/lactose intolerance.

What are the signs and symptoms of cow’s milk allergy?

Milk allergy symptoms can occur within the first few months of human life (within the first 6 months of life), though less commonly symptoms can occur in adulthood. There is a spectrum of severity of milk allergy symptoms, making nailing the diagnosis difficult.

Rapid reaction 

Within hours after consumption of milk. Symptoms include:

• Itchy and tingly lip, mouth throat
• Swelling of the face, lips, tongue, throat, eyes
• Difficulty in breathing
• Wheezing
• Vomiting
• Rashes (hives) on the body
• Anaphylaxis

Delayed reaction

From hours to days after consumption of milk. Symptoms include:

• Abdominal pain and cramps
• Nausea and vomiting
• Diarrhea
• Blood in the stool

Anaphylaxis

An immediate, dangerous fulminant allergic response within seconds to minutes after consumption of milk. Symptoms include:

• Difficulty in breathing
• Facial swelling and flushing
• Swollen throat/ Closing of airway
• Laboured breathing
• Fainty/ Dizziness/ Feeling of impending loom
• Body rash (hives)
• One must seek medical aid immediately as delay in reversing the allergy can be fatal. 

What causes cow’s milk allergy?

Cow’s milk is a rich source of nutrients for the body, with over 20 beneficial proteins.

In milk allergy, the body's immune system reacts to protein that is found in the milk, particularly in 2 types of proteins — casein and whey.

Casein protein is the main emulsifier in milk and it makes up 80% of the protein in cow’s milk and 20-60% of proteins in human milk. Casein is also found in high quantities in cheese, and can be used as a food additive/ emulsifier to stabilise processed food. 

Whey protein is the left over from milk when it is coagulated during the formation of cheese. Whey protein makes up 20% of cow’s milk, and about 60% of human milk. Whey protein is made up of 2 major proteins known as alpha-lactalbumin, beta-lactoglobulin. 

Whey protein is commonly seen in yoghurt and protein supplement (in building muscle mass). Whey protein can also be used as a food thickener.

What type of food commonly has cow’s milk protein?

Common foods with milk protein include:

• fresh cow’s milk
• evaporated/UHT/condensed milk
• butter
• ghee
• cheese
• yogurt
• margarine
• ice cream
• cream
• curds
• calcium or sodium caseinate
• whey powder
• whey protein
• skimmed milk powder
• non-fat milk products
• lactoglobulin
• lactoalbumin

Reading food labels is important to pick up any cow’s milk protein content. If you are eating out, beware of possible milk in the food content. 

Extra caution should be taken if eating out in coffee shops, pizza shops and ice cream places. If in doubt, it is worth highlighting any history of food allergy or food restrictions to the restaurant staff.

How can I diagnose cow’s milk allergy?

A good history with a clear timeline of exposure to milk allergens and presentation of the allergic symptoms is suggestive of cow’s milk allergy. Nonetheless, in the practical world, this can be much more difficult as one may be exposed to other food substances or environmental allergens or symptoms can be confounded with underlying intolerance.

Allergy tests may not be foolproof either, but may facilitate the history of presenting complaints:

• Skin prick test — A quick way of introducing the allergen protein onto the skin to look out for any allergic skin reaction. This can be performed on most patients safely.

• Blood specific-IgE RAST test — A quantitative method to screen for milk protein specific IgE in a person’s blood stream. RAST test is also able to differentiate the type of milk protein (casein/ whey) that one may be allergic to.

• Oral food challenge test — Milk protein is introduced with caution to the patient to monitor for any signs and symptoms of allergy. This should not be attempted at home and should only be done under proper supervision by the health care provider in view of risk of anaphylaxis and possible requirement of resuscitation.

You are advised to discuss any concerning symptoms with your doctor so that they can provide guidance on which tests can be offered to you to evaluate your condition further.

What is the treatment for cow’s milk allergy?

As there are no antidotes for cow’s milk or food allergies, the treatment is by eliminating the culprit allergen — milk from the diet.  

In situations when one has inadvertently consumed milk, medication such as antihistamine and steroid can reduce or abort allergic symptoms. In severe allergic response or anaphylaxis, one will require adrenaline injection or medical emergency to reverse the allergy.

As cow’s milk allergy is commonly seen in children, it is imperative to ensure the child still receives a healthy balanced diet and is taking supplements to replace the common nutrients that are found in milk. 

Breastfeeding is encouraged especially if the infant has cow’s milk allergy. 

As cow’s milk protein can be passed from mother who consumed it to the child through breast feeding, the mother should avoid food that contains cow’s milk protein if the infant has cow’s milk allergy. 

Alternative options such as soy formula milk may not be useful as some children may also have soy protein allergy. Due to high protein allergy cross-reactivity, those with cow’s milk protein are usually not suitable to take goat’s milk as well.

Understanding and determining the allergic components in milk proteins can aid prudent food selections to avoid allergy.

What have I learnt today?

• There are overlapping symptoms between cow’s milk allergy and lactose intolerance. However, the underlying cause and treatment plan for both conditions differ.

• Cow’s milk allergy is more common in children though it can affect adults as well.

• Symptoms of cow’s milk allergy can range from mild gastrointestinal discomfort to severe allergic systemic symptoms involving airway compromise, generalized rash or even anaphylaxis.

• Cow’s milk allergy can be caused by allergenic protein casein and whey.

• Allergy testing can be beneficial in differentiating milk allergy and lactose intolerance when the clinical picture overlaps between the two conditions. 

• Eliminating culprit milk allergen from diet and optimizing of symptomatic relievers are keys in management of milk allergy.

References:

1. Edwards CW, Younus MA. Cow Milk Allergy. [Updated 2023 Jun 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK542243/
2. Regula P, Agress A, Rosenstreich D, Rubinstein A, Ramesh M. Adult-onset IgE-mediated cow's milk allergy-a rare phenotype. J Allergy Clin Immunol Glob. 2023 Jul 8;2(4):100142.
3. https://allergyasthmanetwork.org/food-allergies/milk-allergy/