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PRACTICE: John R Apps and R Mark Beattie Cow’s milk allergy in children BMJ 2009; 339: b2275 [Full text]

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Cow's milk allergy

Judith A Langfield   (10 August 2009)

Challenges are not essential in the diagnosis of cow's milk allergy

Yousuf Karim, Zoe Adhya, Speciality Registrar in Immunology, Royal Surrey County Hospital   (28 August 2009)

Cow's milk allergy 10 August 2009
Judith A Langfield, Retired GP Bristol BS16 2QY Send response to journal: Re: Cow's milk allergy	At last, someone is taking this seriously. It was not until I was 41, that I discovered that I was allergic to cow's milk protein. I had been underweight since childhood, with unexplained bouts of vomiting and diarrhoea, abdominal pain, wheezing, migraine, and overwhelming tiredness. Please do not assume that children grow out of this. I certainly have not. I still react if I consume dairy products accidentally. Competing interests: Allergic to cow's milk protein.
Challenges are not essential in the diagnosis of cow's milk allergy 28 August 2009
Yousuf Karim, Consultant Immunologist Frimley Park Hospital GU16 7UJ, Zoe Adhya, Speciality Registrar in Immunology, Royal Surrey County Hospital Send response to journal: Re: Challenges are not essential in the diagnosis of cow's milk allergy	Dear Editor, Here we respond to several points made in the article by Apps & Beattie on cow’s milk allergy in children (1). The authors state that diagnosis of cow’s milk allergy should be confirmed by challenge, even in those at risk of severe reactions. In practice such confirmation is rarely done as it can be dangerous, is resource consuming, and is often unnecessary if there is a good history, positive test results (skin prick or specific IgE) and improvement with elimination of cow’s milk (2). Oral challenge should be reserved for cases where there is significant diagnostic doubt, and for determining whether a known food allergy has resolved. The authors imply a significant difference in positive predictive testing between specific IgE (sIgE) and skin prick testing (SPT), which is incorrect. Merely having a positive sIgE test does not have a positive predictive value (PPV) of as high as 90-95% as stated. The value of the specific IgE result may be important. The 90% PPV figure refers to having a value of cow’s milk sIgE > 2.5 kU(A)/L in infants less than 12 months (3). The sIgE threshold varies accordingly in different studies: Sicherer and Sampson noted a threshold for milk of 15 kU(A)/ L in children mean age 5 years which could predict clinical reactivity with >95% certainty (4). There are also similar studies assessing the size of a wheal in SPT above which 95% of patients would have an allergic reaction to that food. Conversely, it is also possible to be clinically allergic to cow's milk with a low or even negative sIgE or SPT result. Non-IgE mediated milk allergy is not necessarily a type IV hypersensitivity reaction; in fact the exact immunopathophysiology is unknown(2). 1.Apps JR, Beattie RM. Cow’s milk allergy in children. BMJ 2009;339:b2275 2.Sampson H et al. AGA technical review on the evaluation of food allergy in gastrointestinal disorders. Gastroenterology 2001;120:1026-402. 3.Heine R et al. Cow’s milk allergy in infancy. Curr Opin Allergy Clin Immunol 2002;2:217-25 4.Sicherer S, Sampson H. Food allergy. J Allergy Clin Immunol 2006;117:S470-5 Competing interests: None declared