What is Milk Allergy?
Milk allergy is a reaction of the body’s immune system against milk and milk products. It is most often caused by the alpha S1-casein protein present in cow’s milk. Milk from sheep, goats, buffalo, and other mammals can also cause an allergic reaction in some people.
The overreaction of the immune system results in an allergic reaction. The immune system recognizes the protein in milk as foreign and produces histamine and other chemicals that lead to the symptoms of an allergy.
Milk allergy is the most common food allergy in children. Milk is one of the 8 types of food that cause 90% of allergies in children. Most children outgrow the allergy before adolescence.
Milk allergy is usually confused with lactose intolerance because of common symptoms. They’re not the same condition. Lactose intolerance is caused by the absence of an enzyme called lactase, needed to metabolize a milk sugar called lactose. Milk allergy is an allergic reaction to a protein present in milk.
Some people are allergic to almond milk or soy milk as well, which are commonly used as alternatives to cow’s milk. The right trigger of the reaction should be identified to manage the allergy.
Signs and symptoms are usually very mild and can be easily managed. The allergy can be life-threatening in rare cases where there is a severe allergic reaction like anaphylaxis. This impairs breathing and can send the body into shock if immediate action is not taken. Anaphylaxis can also lead to cardiac arrest.
If you’re allergic to milk, you may be at an increased risk of other food allergies like eggs, peanut or beef allergy, allergies to pet dander, pollen, or dust mites, which causes hay fever.
Symptoms of Milk Allergy
The symptoms vary from person to person and can usually occur immediately after consumption or after a few hours. The symptoms are common to those seen in other allergic reactions.
- Skin rash
- Diarrhea
- Wheezing
- Vomiting
- Hives
- Cough, sinus infection
- Swelling of lips and tongue
- Itching of lips and mouth
- Watery eyes
- Colic in babies
- Anaphylaxis in severe cases
The Genetics Behind Milk Allergy
Variations in certain genes have been observed in people with milk allergies. Studying these variations can help predict if a person has a higher risk of getting the allergy compared to other people.
IL2 Gene
The IL2 gene encodes a cytokine called interleukin 2, which is part of immune signaling in the body. It is involved in regulating white blood cells and is also a part of the body’s immune response against foreign bodies like microbes. Mutations in this gene have been found to be associated with milk allergy.
rs2069772
rs2069772 is an SNP found in the IL2 gene. The T allele is found in people who are allergic to cow’s milk.
TLR6 Gene
The TLR6 gene encodes a protein called toll-like receptor 6. This protein plays a major role in innate immunity, which is the first non-specific defense by the immune system against a foreign body. TLR6 is also involved in recognition of pathogens like bacteria and fungi. They trigger the immune system to produce chemicals necessary to fight the pathogens. Mutations in this gene have been found to be associated with milk allergy.
rs17616434
rs17616434 is an SNP found in the TLR6 gene. The C allele is found in people who are allergic to cow’s milk.
Non-Genetic Factors that Influence Milk Allergy
Age: Children are more prone to milk allergy. Allergic reactions are less likely to occur in older people.
Atopic dermatitis: Children who have this skin problem are more likely to develop a food allergy.
Pre-existing conditions: Any food allergy or other allergic diseases like asthma, hives, or eczema increases the risk of milk allergy.
Non-Genetic Factors that Influence Milk Allergy
Age: Children are more prone to milk allergy. Allergic reactions are less likely to occur in older people.
Atopic dermatitis: Children who have this skin problem are more likely to develop a food allergy.
Pre-existing conditions: Any food allergy or other allergic diseases like asthma, hives, or eczema increases the risk of milk allergy.
Diagnosing Milk Allergy
Skin-prick test: A small amount of liquid containing milk protein or milk protein extract is allowed to seep into the skin on the back or forearm by piercing. After 15-20 minutes, if signs of allergy like redness, raised welt are observed, the person is said to be allergic to milk.
Blood test: Blood sample is tested for the presence of allergic antibodies against milk protein. A newer type of blood test called component test is used to look for severe allergic reactions to specific proteins in milk.
Oral food challenge: Small amount of milk or milk powder is consumed under the supervision of an allergist or trained staff to see if any reaction occurs.
Managing Milk Allergy
The best way to manage any allergy is to avoid the allergen causing it. This can prevent severe allergic reactions.
Food products: Start reading the labels on food products. Look for casein, a milk derivative that is also found in tuna, sausages, and other non-dairy products. The other main milk protein to look out for is whey.
Several food items are marked as milk-free or non-dairy but can contain certain milk proteins or derivatives that can lead to allergies.
Make a list of all the products that contain milk or related proteins and avoid them.
Milk alternatives: For cooking or baking, milk can be easily substituted with water, juice, or other types of milk like soy or rice milk. Soy or rice milk can also cause an allergic reaction in some people.
If an infant is allergic to milk, the doctor would recommend hypoallergenic formulas that contain milk proteins broken down by enzymes. Depending on the level of breakdown, they are classified as partially, extensively hydrolyzed, or elemental formula. Amino acid-based formulas are also available. Talk to a doctor about what alternative would be best for your infant.
Allergy bracelet or necklace: Children should wear an allergy bracelet or necklace that informs people of the allergy, especially if the child can develop a serious reaction to milk.
Severe allergic reactions: Epinephrine in an auto-injector is usually used to treat anaphylaxis, which is a severe allergic reaction. This should be carried with a person susceptible to severe allergic reactions and used when symptoms start to occur.
Summary
- Milk allergy is a reaction of the body’s immune system against the protein present in milk. They are treated as a foreign substance and attacked by the immune system. Most children outgrow their symptoms as they grow old except in certain cases. Casein and whey are two milk proteins that are common causes of milk allergy in children.
- The symptoms of egg allergy are common to other allergies. Few symptoms are redness, wheezing, hives, and shortness of breath.
- Variations in certain genes are found to increase the risk of milk allergy. The T allele of rs2069772, an SNP found in the IL2 gene, and the C allele of rs17616434, an SNP found in the TLR6 gene, are known to increase your risk for milk allergy.
- There are a few tests that can be done to find out if the milk proteins are a trigger for your allergic reactions.
- The best way to prevent symptoms is to avoid the consumption of milk and related products. Make sure you know the ingredients present in the food you’re eating. Substitutes can be used in cooking, and hypoallergenic formulas can be used for infants.
References
https://www.healthline.com/health/allergies/milk
https://acaai.org/allergies/types-allergies/food-allergy/types-food-allergy/milk-dairy-allergy
https://www.mayoclinic.org/diseases-conditions/milk-allergy/symptoms-causes/syc-20375101
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4776421/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4340086/
https://www.genecards.org/cgi-bin/carddisp.pl?gene=IL2
https://www.genecards.org/cgi-bin/carddisp.pl?gene=TLR6
