Cow’s Milk Allergy: A Complex Disorder

Abstract

Cow’s milk allergy (CMA) is a complex disorder. Numerous milk proteins have been implicated in allergic responses and most of these have been shown to contain multiple allergenic epitopes. There is considerable heterogeneity amongst allergic individuals for the particular proteins and epitopes to which they react, and to further complicate matters, allergic reactions to cow’s milk are driven by more than one immunological mechanism. Finally, the incidence and dominant allergic mechanisms change with age, with IgE-mediated reactions common in infancy and non-IgE-mediated reactions dominating in adults. The complexity of CMA has lead to many public misconceptions about this disorder, including confusion with lactose intolerance and frequent self-misdiagnosis. Indeed, the prevalence of self-diagnosed CMA in the community is 10-fold higher than the clinically proven incidence, suggesting a sizable population is unnecessarily eschewing dairy products. Avoidance of dairy foods, whether for true or perceived CMA, carries with it nutritional consequences and the provision of appropriate nutritional advice is important. In this review, the epidemiology and natural course of CMA is discussed along with our current understanding of its triggers and immunological mechanisms. We examine current strategies for the primary and secondary prevention of allergic sensitization and the ongoing search for effective therapies to ultimately cure CMA.

• CMA
• milk proteins
• allergy
• breast-feeding

• CMA = cow’s milk allergy
• CMI = cow’s milk intolerance
• DBPCFC = double-blind, placebo-controlled food challenge
• eHF = extensively-hydrolyzed formulas
• GALT = gut-associated lymphoid tissue
• IgE = immunoglobulin E
• IL-10 = interleukin-10
• pHF = partially-hydrolyzed formulas
• RAST = radioallergosorbant test
• SPT = skin prick test
• TGF-β = transforming growth factor-beta
• Th1 = T helper cell-type1
• Th2 = T helper cell-type 2
• T reg = regulatory T cell

Key teaching points:

• Cow’s milk allergy is an inflammatory response to milk proteins and is distinct from lactose intolerance.

• CMA is more prevalent in infants (2–6%) than in adults (0.1–0.5%), and the dominant immunological mechanisms driving allergic reactions change with age.

• The prevalence of self-diagnosed CMA in the community is substantially higher than the incidence reported in blinded and controlled challenge trials, suggesting that a proportion of the population is unnecessarily eschewing dairy products

• Breast-feeding is the best preventative strategy, although it cannot eliminate the risk of allergic sensitization in infants.

• Management of CMA involves avoidance of dairy during the duration of the disease, and the provision of appropriate nutritional advice is important to prevent nutritional deficiencies, particularly for parents of young children who have dairy withdrawn from their diet due to either diagnosed or perceived CMA.

Key teaching points:

• Cow’s milk allergy is an inflammatory response to milk proteins and is distinct from lactose intolerance.

• CMA is more prevalent in infants (2–6%) than in adults (0.1–0.5%), and the dominant immunological mechanisms driving allergic reactions change with age.

• The prevalence of self-diagnosed CMA in the community is substantially higher than the incidence reported in blinded and controlled challenge trials, suggesting that a proportion of the population is unnecessarily eschewing dairy products

• Breast-feeding is the best preventative strategy, although it cannot eliminate the risk of allergic sensitization in infants.

• Management of CMA involves avoidance of dairy during the duration of the disease, and the provision of appropriate nutritional advice is important to prevent nutritional deficiencies, particularly for parents of young children who have dairy withdrawn from their diet due to either diagnosed or perceived CMA.

Financial support provided by Dairy Australia for milk protein allergy research at Food Science Australia is gratefully acknowledged.