There is often great confusion regarding cow’s milk allergy (CMA) and Lactose Intolerance, with the terms often used interchangeably despite both being separate disorders and very distinct.
As described above, food allergies such as cow’s milk allergy are a form of food intolerance that involves the immune system. Lactose intolerance describes a form of food intolerance caused by deficiency of a specific enzyme and does not involve the immune system- see section on lactose intolerance for more information.
Cow’s milk allergy is caused by an abnormal immune response to harmless milk proteins and generally results in the rapid appearance of symptoms after consumption of cow’s milk.
Despite some similarities between the proteins found in human and bovine milks, cow’s milk proteins can still be recognised as “foreign” by the human immune system.
In the majority of individuals the immune system recognises these proteins as harmless and tolerates them in the body, however in CMA individuals, the immune system becomes sensitized and reacts to the proteins by mounting a damaging inflammatory response.
Types of cows milk allergy
Cow’s milk allergy (CMA) is often divided into cow’s milk protein allergy (CMPA) where there is clear evidence of involvement of the immune system, and cow’s milk protein intolerance (CMPI) where there is no involvement of the immune system.
Allergies to milk are broadly classified into immunoglobulin E (IgE)-mediated allergy, and non-IgE mediated allergy.
IgE-mediated allergy is commonly referred to as “immediate hypersensitivity” as the onset of symptoms occurs within minutes to an hour following exposure to the allergen (in this case protein).
Non-IgE-mediated CMA reactions are usually “delayed” with the onset of symptoms occurring from 1 hour to several days after ingestion of milk; hence it is often called a “delayed hypersensitivity”.