Milk allergy and other food allergies are defined by The National Institute for Allergy and Infectious Diseases (NIAID) as “an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food”.1

Immune-mediated milk and other food allergies are classified as either imumunoglobulin E (IgE) mediated 2 or non-IgE mediated 2, based on the mediating immune system response and the presentation and symptoms. There may also be a clinical overlap between some food allergy presentations; these are classified as mixed IgG and non-IgE-mediated allergies.1

IgE mediated
eg acute urticaria, oral allergy syndrome
Non-IgE mediated
eg food protein-induced, enteropathy, coeliac disease
Mixed IgE and non-IgE mediated
eg eosinophilic gastroenteritis
Cell mediated
eg allergic contact dermatitis
eg lactose intolerance
eg caffeine
eg scombroid fish toxin
eg sulfites

Adapted from Boyce et al. 2010.1

Diagnosing and managing cows’ milk allergy

Diagnosing and managing cows’ milk allergy

In Australia and New Zealand, the Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional society of clinical immunology and allergy specialists. ASCIA has developed a number of educational resources to help health professionals and patients understand, prevent and treat allergic diseases, including cows’ milk protein allergy. Health professionals can visit the ASCIA website to review the associated symptoms presenting as a range of syndromes. ASCIA also provide information on appropriate immunological and morphological studies needed to reach a correct diagnosis. In May 2016, ASCIA released new infant feeding and allergy prevention guidelines. In these guidelines, partially and extensively hydrolysed infant formula are not recommended for the prevention of allergic diseases.

Briefly, diagnosis of an IgE-mediated immunological response is most often made on clinical grounds supported by standard diagnostic tests such as skin prick tests (SPT) or serology for antigen-specific IgE testing. This can be confirmed by oral challenge, but a positive test coupled with a clear history of a reaction is usually sufficient to confirm a diagnosis.3 Management of cows’ milk allergy can be complex, with even trace amounts of cows’ milk protein capable of eliciting an allergic reaction. First-line management involves complete avoidance of cows’ milk and any of its products. While cows’ milk protein allergy is usually outgrown during early childhood, in some cases it persists into adulthood.

Most gastrointestinal cows’ milk allergy syndromes are non-IgE associated.4 Non-IgE or cell-mediated reactions are not detected using the standard diagnostic tests (SPT or antigen-specific IgE testing). Instead, these are confirmed with a thorough clinical history followed by elimination of the suspected food allergen and observed resolution of symptoms. If diagnosis remains uncertain, further confirmation can be achieved by challenging with cows’ milk under medical supervision and observing relapse.

Perceived cows’ milk protein allergy

Perceived cows’ milk protein allergy is reportedly more than 5-fold higher than that detected by accepted diagnostic tests and protocols.5 This difference could be explained in part by some of those with perceived cows’ milk protein allergy expressing symptoms associated with non-IgE-mediated reactions, which may take time to diagnose (i.e. cows’ milk protein elimination and observed resolution of symptoms) and may escape initial detection.

An alternative explanation is that for some patients who have outgrown their cows’ milk allergy, gastrointestinal symptoms may persist following lactose-free cows’ milk intake.6