Background: Although cow's milk allergy (CMA) and cow's milk intolerance (CMI) are two different terms, they are often used interchangeably, resulting in confusion both in clinical practice and in research reports.
Objective: To promote the appropriate differential use of the terms CMA and CMI.
Methods: Highlighting the differences in clinical and laboratory findings between CMA and CMI. Information was derived from reviewing the literature on these two topics, supplemented by the clinical experience of the author.
Results: CMA is an immunologically mediated reaction to cow's milk proteins that may involve the gastro-intestinal tract, skin, respiratory tract, or multiple systems, ie, systemic anaphylaxis. Its prevalence in the general population is probably 1 to 3%, being highest in infants and lowest in adults. Even though it can cause severe morbidity and even fatality, dietary elimination is associated with good prognosis. However, CMI should refer to nonimmunologic reactions to cow's milk (CM), such as disorders of digestion, absorption, or metabolism of certain CM components. The most common cause of CMI is lactase deficiency, which is mostly acquired during late childhood or adulthood. It has high racial predilection, being highest in dark-skinned populations and lowest in northern Europeans. Lactose intolerance is generally a benign condition, with symptoms limited to the gastro-intestinal tract, yet the primary acquired type lasts for a lifetime. Symptoms can be well ameliorated by reducing the intake of CM or using lactose-hydrolyzing agents.
Conclusions: Adverse reactions to CM should be differentiated into immunologic (CMA) and nonimmunologic (CMI). The latter is still a general term that comprises several conditions and requires further differentiation.