Which condition involves the immune system rather than an enzyme deficiency?

A milk allergy is a condition that involves the immune system as it is an allergic reaction to proteins found in milk. In this case, when a person with a milk allergy consumes milk, their immune system mistakenly identifies the proteins as harmful, leading to an immune response. This can result in symptoms such as hives, digestive issues, or even anaphylaxis, which is a severe, life-threatening reaction.

In contrast, the other options relate to digestive issues primarily caused by enzyme deficiencies or reactions that do not involve the immune system in a similar manner. For example, lactose intolerance results from a deficiency in lactase, the enzyme that breaks down lactose, leading to digestive discomfort without an immune response. Celiac disease does involve the immune system, but it specifically relates to a reaction to gluten, rather than being a straightforward food allergy. Food intolerance refers to a variety of non-immune related reactions to foods, including digestive upset. Thus, a milk allergy distinctly represents an immune system response.