Lactose Intolerance and Cows’ Milk Protein Allergy
Claire Schwarz, Research Dietitian, Great Ormond Street Hospital, London
Lactose Intolerance (LI) and Cows’ Milk Protein Allergy (CMPA) are terms often used interchangeably when infants and children have adverse gastrointestinal reactions to dairy products. However, these are two distinctly different conditions and careful consideration should be given to the appropriate clinical use of these diagnostic terms. Both fall under the remit of food hypersensitivity, as defined by two scientific reports1,2 (Figure 1), but have different pathophysiology. It is vital that paediatric health professionals understand the differences between LI and CMPA, use appropriate terminology, and understand the diagnosis and treatment pathways for each.
Definition and clarification of terms
Lactose, a disaccharide, is the predominant carbohydrate found in mammalian milk. To be effectively utilized, it must be hydrolysed by lactase to produce galactose and glucose3. A marked reduction in lactase in the intestinal brush border (lactase deficiency), results in lactose malabsorption. Lactose intolerance (LI) describes the symptoms that occur a result of lactose malabsorption e.g. abdominal distension, flatulence, abdominal cramping and diarrhoea4,5. LI is therefore not immune mediated, but is a result of lactase deficiency (LD).
Two main types of LD exist. Primary LD occurs in up to 70% of humans and is attributable to decreased lactase activity. This normally only becomes apparent in mid childhood, although the decline of lactase occurs at varying rates and between different ethnic groups3. By age 16 most people of non Caucasian heritage will be at least partially intolerant. Secondary LD results from injury to the intestinal villi within the small bowel, causing subsequent loss of lactase activity, e.g. acute gastroenteritis and gastrointestinal enteropathies. This is usually transient, resolving within a few weeks6.
CMPA is an immune mediated reaction, occurring when cows’ milk protein elicits an immunological response at presentation7. The prevalence varies between 1.9% - 4.9%7,8, and can be IgE-mediated (immediate reaction) or non-IgE- mediated (delayed reaction). CMPA allergy induces symptoms affecting the gastro-intestinal (GI) tract, skin, and respiratory tract. These include anaphylaxis, GI symptoms including: nausea, vomiting, abdominal pain/ cramping, diarrhoea and bloody stools; also urticaria, angio- oedema, acute dermatitis, and occasionally malabsorption and weight loss6,7.
Table 1 tabulates the classification and symptoms of food hypersensitivity in context of IgE- and non-IgE reactions9.
How do we identify and treat LI?
Diagnostic tools for LI include hydrogen breath tests, along with tests for stool reducing substances8. However in clinical practice these are not always performed. A good medical and symptom history is crucial in diagnosing any food hypersensitivity, including LI and CMPA. Trialling a lactose free diet is useful in suspected primary LI. ESPGHAN guidelines do not recommend it for transient secondary intolerance. Lactose- containing foods are eliminated and then slowly and incrementally reintroduced to tolerance. Symptom improvement when avoiding lactose indicates LI, provided other causes have been excluded.
How do we identify and treat CMPA?
Diagnosing CMPA is not always straightforward. IgE-mediated CMPA is diagnosed by skin prick tests, measurements of specific serum IgE levels (SpIgE) and a detailed clinical history. An elimination diet and subsequent food challenge confirms diagnosis9. Non-IgE-mediated CMPA diagnosis is somewhat more challenging. Skin prick tests and Specific IgE’s are frequently negative, therefore an elimination diet is used as the main diagnostic tool9,10.
May 12, 2014 - 08:02 AMHow did the Irish Food Allergy Network (IFAN) come about?
I noticed increasing numbers of infants and toddlers presenting with suspected food allergy at my HSE based dietetic clinic from 2000, a time when there was a massive “black hole” in national allergy services. Families were struggling to cope not to mention me as a DIetitian. The associated burden of care and quality of life issues for affected families were huge and significant.