Lactose intolerance is a physiological response to poorly digested and/or absorbed lactose in the gut due to lactase deficiency or inactivity. This does not involve the immune system, sticking to causing issues in a child’s digestive system.⁶

In contrast, cow’s milk protein allergy is an adverse immune system reaction to cows’ milk protein that can be either immunoglobulin E (IgE) or non-IgE mediated.⁶ Although their symptoms may be similar in some cases, intolerance is not the same as an allergy. An allergy can cause a severe allergic reaction and anaphylactic shock, whereas intolerances usually do not cause such a reaction.⁷

Lactose intolerance and cow’s milk protein allergy are often incorrectly used interchangeably due to similarities in the gastrointestinal clinical symptoms.³ Misdiagnosis or delayed diagnosis may result in inappropriate treatment options and/or unnecessary dietary restriction.³