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Whey and casein specific IgE and the cow's milk challenge test for atopic children
1Department of Pediatrics and Medical Research, Mackay Memorial Hospital, Taipei, Taiwan, R.O.C.
Insights
Many atopic children with IgE antibodies to cow's milk proteins tolerate milk. Food challenges confirmed tolerance, indicating RAST testing alone is insufficient for diagnosing milk allergy in children.
Area of Science:
- Pediatric Allergy
- Immunology
- Clinical Nutrition
Background:
- Atopic children often exhibit allergic conditions like asthma, eczema, and rhinitis.
- Cow's milk allergy is a common concern in this population.
- Elevated IgE antibodies to cow's milk proteins are frequently observed.
Purpose of the Study:
- To investigate the clinical relevance of IgE antibodies to cow's milk proteins in atopic children.
- To determine if these children tolerate cow's milk despite positive allergy tests.
- To assess the diagnostic utility of RAST FEIA compared to food challenges.
Main Methods:
- Screened 30 atopic children with suspected milk allergy using Pharmacia CAP system RAST FEIA.
- Identified children with IgE antibodies (Class II) specific to cow's milk proteins (casein, alpha-lactalbumin, beta-lactoglobulin).
- Conducted a 3-week cow's milk elimination diet followed by milk challenge tests.
Main Results:
- All 30 children had IgE antibodies to cow's milk proteins.
- Specific IgE antibodies were detected against casein, alpha-lactalbumin, and beta-lactoglobulin in varying combinations.
- None of the children exhibited significant allergic reactions upon milk challenge post-elimination diet.
Conclusions:
- Cow's milk proteins like casein, alpha-lactalbumin, and beta-lactoglobulin can all elicit IgE responses.
- Many atopic children with positive IgE tests to cow's milk can tolerate it.
- Double-blind placebo-controlled food challenges are essential for confirming milk allergy diagnoses.
Abstract:
We studied 30 atopic children who suspected of milk allergy by past history (age ranging from 1 yr 4 mo to 9 yr 6 mo, mean age: 5.03 yr.) diagnosed as having asthma, atopic dermatitis and/or allergic rhinitis. These 30 atopic children had been screened from the patients at our outpatient clinic by the Pharmacia CAP system RAST FEIA. All of them showed the presence of at least Class II (greater than 0.7 ku/l) IgE specific to proteins in cow's milk. Further analysis found IgE specific to alpha-lactoalbumin (alpha-LA) elevated in 1 patient (3.3%), 1 patient (3.3%) to beta-lactoglobulin (beta-LG), 4 patients (13.3%) to alpha-LA and beta-LG, 5 patients (16.7%) to casein, 8 patients (26.7%) to casein and alpha-LA, 11 patients (36.7%) to casein, alpha-LA and beta-LG. After 3 weeks' cow-milk-free diet, the patient's milk challenge test was performed at our outpatient clinic. According to the test result, none of these 30 atopic children showed clinical evidence of significant allergic reaction to cow's milk in the skin, the gastrointestinal tract or the respiratory tract either within two hours after the challenge test or within 3 days after they went home. We therefore conclude that: (1) No single major allergen is apparent in cow's milk: casein, alpha-LA and beta-LG all show a high proportion of positive reaction. (2) Many atopic children fully tolerate cow's milk, although they have high titer of IgE antibodies specific to cow's milk. The RAST test is only the first step to screen patients with suspected IgE-mediated allergies. To make sure, any positive reaction must be confirmed by the "golden standard" for diagnosis, i.e., the double-blind placebo-controlled food challenge.