Milk known as Doodh (Hindi), Halu (Kannada), Pal (Tamil/Malyaalam), Pala (Telugu) causes allergies in about 0.05% of our population.
Cow’s milk contains around 30-35 grams of proteins/litre of about 25 different varieties. Any of these proteins may act as an allergen. These proteins are broadly divided into caseins (80%) and serum (whey) proteins (20%).
- The major allergenic milk proteins are:
- Caseins (Bos d 8, which is a combination of Bos d 9 to Bos d 12)
- Beta-lactoglobulin (Bos d 5) and
- Alpha-lactalbumin (Bos d 4)
- The other characterised allergenic milk proteins are:
- Caseins: alpha s1 (Bos d 9), alpha s2 (Bos d 10), beta (Bos d 11), kappa (Bos d 12)
- Whey: bovine serum albumin (Bos d 6), immunoglobulins (Bos d 7), lactoferrin.
Cross reactivity: Cow’s milk allergens cross reactivity with milk of other mammals such as goats, sheep and buffalo. Milk from non/bovid mammals (mare,donkey,camel) shows better tolerance in some patients. Bovine serum albumin (Bos d 6) may cross react with raw beef, but is lost on cooking being heat sensitive.
CMPA (Cow’s Milk Protein Allergy) are amongst the most common food allergies in all age groups. The prevalence of CMPA (estimated) in the first year of life is 1.6-3%, and decreases to less than 1% in children aged 6 years or older. Majority of the CMPA patients outgrow their condition. Children who out grow of their CMPA become tolerant to milk in baked form before fresh milk products as baking reduces protein allergenicity.
Allergy to milk may manifest as an IgE mediated, non-IgE mediated or mixed manifestations. Typical IgE-associated symptoms appear immediately or within 1-2 hours after milk ingestion and affect the skin, the respiratory system, the GI tract and/or appear as systemic anaphylactic reactions in severe cases. Milk is the third most common food after peanuts and tree nuts that causes anaphylactic reactions, accounting to 10-19% of all food-induced anaphylactic cases.
In non-IgE mediated disease the clinical symptoms affect mainly the gastrointestinal system including enterocolitis, proctitis, proctocolitis, enteropathy, irritable bowel syndrome, eosinophilic esophagitis and constipation. Respiratory symptoms and atopic dermatitis may also be seen (less commonly) in this presentation. The clinical manifestations of mixed manifestations may appear as atopic dermatitis and eosinophilic gastroenteropathies (esophagitis and gastroenteritis).
