ORIGINAL ARTICLES
Egg and milk allergy in asthmatic children: assessment by immulite allergy food panel, skin prick tests and double-blind placebo-controlled food challenges
M. Yazicioglu*, I. Baspinar**, Ü. Önes***, Ö Pala**** and U. Kiziler****
*Associate Professor of Pediatrics, Department of Pediatrics, Trakya Faculty of Medicine. Edirne. Turkey. **Research Assistant in Pediatrics, Trakya Faculty of Medicine. Edirne. Turkey. ***Professor of Pediatrics, Allergy Clinic of the Department of Pediatrics, Istanbul Faculty of Medicine. Istanbul. Turkey. ****Professor of Pediatrics, Department of Pediatrics, Trakya Faculty of Medicine. Edirne. Turkey. *****General Practitioner, Trakya Faculty of Medicine. Edirne. Turkey.
Correspondence:
Dr. Mehtap Yazicioglu
Konaklar mah., Sögüt sok.,
Petek Sitesi, GB Blok, Daire 18
Yenilevent 80620
Istanbul
Turkey
E-mail: yazicioglu@superonline.com
SUMMARY
There is a perception that asthmatic symptoms may be worsoned by ingestion of certain foods. This study aimed to investigate whether ingestion of cow''s milk or egg might induce respiratory symptoms in asthmatic children. Fifty asthmatic children aged 1.5 to 6 years old, with positive Immulite Food Panel FP5 test results were included in the study. Fifty healthy children within the same age group were accepted as control group. Total serum IgE levels were measured and skin prick tests for food allergens including milk and egg were performed. All of the subjects underwent oral, double-blind, placebo-controlled challenge with fresh egg and cow''s milk powder. Two medical histories were confirmed by double-blind, placebo-controlled challenge in 9 patients (22.2%). Skin prick tests were positive in 9 patients (18%) with milk and 18 patients (36%) with egg antigen. Two children experienced wheezing, one after ingesting milk and the other after egg challenge (4%). In the control group no positive reactions were seen with egg or milk challenges. Our findings confirm that food allergy can elicit asthma in children, but its incidence is low, even with major allergens such as egg and milk. History, specific IgE determinations and skin prick tests are not reliable in diagnosing food reactions. Since any diet can cause rapid deficiencies in infancy, diet restrictions must not be applied, without performing double-blind, placebo-controlled challenge.
Key words: Allergy. Children''s asthma. Cow''s milk. Egg.
INTRODUCTION
Food allergy is one of the causes of atopica dermatitis, of acute urticaria, of reactions of the gastro-intestinal tractus, and of acute systemic anaphylaxis. Its role in asthma appears to be less clear. Some investigators estimate that it is a frequent cause of asthma in children or adults, whereas other investigators believe it is unimportant (1). On the other hand, unnecessary elimination diets may have nutritional consequences, and hypoallergenic diets may be expensive for the families (2). Accurate diagnosis of food allergy is therefore essential.
In our study we planned to investigate the role of major food allergens, egg and milk (1, 3, 4), on asthmatic symptoms. Since history is not reliable (3, 5, 6), we included the children whose food screening test (Immulite Food Panel FP5) was positive. Nine of these children also had positive history of respiratory reactions provoked by ingestion of milk and/or egg. Double blind placebo controlled food challenges (DBPCFCs) and skin prick tests (SPTs) were performed in order to determine whether the results of immunologic tests correlated with the development of clinical hypersensitivity and the role of most prevelant food allergens, egg and milk in asthma were evaluated.
PATIENTS AND METHODS
Fifty asthmatic children, 27 male and 23 female, with a median age of 5 years (range 1.5 to 6), attending the Department of Pediatrics of Trakya Faculty of Medicine (Turkey) between December 1995 and December 1997, whose food specific IgE screening test (Immulite FP5) was positive were enrolled in the study. Nine of the patients also had a positive history of asthmatic reaction to milk and/or egg. No other asthmatic patients under investigation in our clinic reported respiratory symptoms after ingesting these foods. Asthma was diagnosed according to the criteria of the American Thoracic Society (7). The patients with foreign body aspiration syndromes, tuberculosis, cystic fibrosis, gastro-oesophageal reflux, and vascular ring associated with wheezing were excluded.
Fifty children, 27 male and 23 female, with a median age of 5 years (range: 1 to 6), without a history of recurrent infections, asthma or allergy and whose Immulite FP5 tests were negative were selected as controls.
None of the patients had received specific immunotherapy before or during the study. Informed consent was obtained from the parents for all the participants in the study.
A detailed history of allergic diseases investigating particularly the possible symptoms of food allergy and intolerance such as atopic dermatitis, acute urticaria, angioedema, acute anaphylaxis, gastrointestinal involvement was obtained from each patient.
Total serum IgE
Immulite Total IgE was measured by a solid-phase, two-site chemiluminescent enzyme immunometric assay (Diagnostic Products Corporation, Los Angeles, USA), according to the package insert.
Immulite Allergy Food Panel FP5E
Specific IgE antibodies to a panel of food allergens (egg, white, milk, codfish, wheat, peanut, soybean) were qualitatively detected by chemiluminescent enzyme-labeled immunoassay using Immulite Allergy Food Panel FP5E kit (Diagnostic Products Corporation, Los Angeles, USA), according to the test procedure.
Skin prick tests
Skin tests were performed by the prick method in all cases in asthma and control group. Glycerinated whole hen''s egg 1:20 w/v and cow''s milk (raw and pasteurized) 1:20 w/v, histamine hydrochloride 10 mg/ml, and diluent/negative control, (ALK-Allergologisk Laboratorium, Denmark) were applied to the patient''s volar surface of the forearm. The reactions were recorded after 15 minutes and a wheal diameter 3 mm larger than the wheal diameter of the negative control was considered a positive reaction. All the children tested had positive control (histamine) wheals larger than 3 mm. None of the patients was under treatment that might modify skin tests.
Placebo-controlled DBFC
Prior to testing all subjects discontinued asthma medications as suggested by Sampson et al (8). Milk and egg were eliminated from the diet for 2 weeks before testing.
All challenges were performed in a double-blind, placebo-controlled fashion in a manner similar to that reported by Norgaard et al (9), and Baehler et al (10) with slight modifications. The patients were challenged only when free of symptoms and in fasting state. All challenge phases were performed in a specialized hospital unit, where appropriate medication and resuscitation equipment were directly available. Challenge constituents comprised fresh hen''s egg and cow''s milk powder bought locally.
Active challenges with egg contained between 0.5 g to 50 g of whole egg. The boiled egg was concealed in a vehicle of lactose-free soy and beef hydrolysate based formula (Pregomin, Milupa) and dextrose solution (50 g dextrose/L). Doses ranging from 0.5 g to 50 g were concealed in 100 to 250 ml of the vehicle. In the placebo challenges diluted egg was substituted by equal volumes of glucose solution. Active and placebo solutions were randomly labelled as A or B, in order to blind the family and the medical team. The appearance of the active and placebo material was similar, satisfactorily maintaining the blinded nature of the challenge. Increasing quantities were administered orally every 30 min, such as 0, 0,5 g, 5 g, 50 g.
Challenges with milk were prepared in essentially the same manner and administered one week later. 250 ml of the dextrose solution was mixed with semi-elemental formula (Pregomin) and 10 g milk powder as active challenge, or milk powder was substituted by equal volume of glucose as placebo, labelled as milk A or B, in a random and blinded fashion. Increasing quantities were administered orally every 15 min, according to the following schedule: 1 drop, 0.5 ml, 1 ml, 2.5 ml, 5 ml, 10 ml, 20 ml, 30 ml, 60 ml. Active or placebo challenges were carried out separately, one in the morning, and the second in the afternoon.
All patients were clinically followed by a physician for 4 hours after the challenge. If no reaction ensued, the patient returned home 4 h after the beginning of the second part of the DBPCFC. When objective signs appeared (positive challenge), the challenge was stopped and treatment was given if required. Objective symptoms included cutaneous reactions (urticaria and/or pruritic, erythematous, morbiliform rashes), gastrointestinal reactions (nausea, abdominal pain, emesis and/or diarrhoea), or respiratory reactions (rhinoconjunctivitis, laryngeal edema/tightness and dysphonia; and dyspnoea, cough, wheezing, and chest tightness) (11). It was not possible to evaluate the patients by spirometry since they were too young to perform these tests adequately. The patient was considered clinically tolerant to the food if a dose of 50 g of egg and 10 g milk powder (corresponding to approximately 250 ml of cow''s milk) produced no objective symptoms during challenge.
If the challenge result was positive, children were kept in the hospital for 12-24 hours according to the course and severity of the symptoms. If the challenge results was negative, parents were asked to openly give these foods to the children at home for 4 days and to fill in a diary card with a score for clinical symptoms.
Statistical Analysis: statistical analyses were made using Mann-Whitney U test, and X2 test and Fisher''s test.
RESULTS
The data on age and sex, and the results of total serum IgE determinations, food specific IgE screening by the Immulite FP5 test and SPTs with egg and milk antigens for patient and control groups are given in table I. The mean (± SD) ages of the patient and control groups were 4.61 ± 1.35 and 4.27 ± 1.50 years, respectively; there was no significant difference either in age or sex distribution between the two groups.
| Table I Characteristics of the patients in asthma and control group | ||||
| Asthma group (n = 50) | Control group (n = 50) | Statistical evaluation | ||
| Age (years) | Mean ± SD | 4.61 ± 1.35 | 4.27 ± 1.50 | |
| Median | 4 | 4 | p = .29 | |
| Range | 1.5-6 | 1-6 | ||
| Male | 27 (54%) | 27 (54%) | ||
| Sex | p = 84 | |||
| Female | 23 (46%) | 23 (46%) | ||
| Total serum IgE | Mean ± SD | 480.53 ± 621.30 | 60.69 ± 61.22 | |
| Median | 222 | 38.65 | p = .00 | |
| Range | 7.70-2829 | 7-268 | ||
| Positive | 50 (100%) | | ||
| IMMULITE FP5 | p < .00 | |||
| Negative | | 50 (100%) | ||
| + | 9 (18%) | 4 (8%) | ||
| SPT with milk | p = .12 | |||
| | 41 (82%) | 46 (92%) | ||
| + | 18 (36%) | 4 (8%) | ||
| SPT with egg | p < .00 | |||
| | 32 (64%) | 46 (92%) | ||
| + | 9 (18%) | | ||
| History of asthmatic reactions with egg and/or cow''s milk | | 41 (82%) | 50 (100%) | p < .00 |
The mean (± SD) total serum IgE concentrations were 480.53 ± 621.30 IU/ml (median, 222; range, 7.10 2829) in the patient group and 60.69 ± 61.22 IU/ml (median, 38.65; range, 7 268) in the control group, the difference being significantly high (p = .00). The Immulite FP5 test result was positive in 50 of the patients and none of the controls.
The skin test results were positive in 9 cases (18%) with milk antigen (raw or pasteurized) and in 18 cases (36%) with egg antigen in the patient group. In the control group, skin-test results were positive in 4 cases (8%) with milk (raw or pasteurized) and in 4 cases (8%) with egg antigens. Two of 9 patients whose skin tests with milk extracts were positive also had history of respiratory reactions such as cough and wheezing with milk ingestion. The positive history of egg related respiratory symptoms were 6 in 18 cases with skin test positivity.
In the patient group, DBPCFC reproduced wheezing in one case with milk and in another case with egg. The asthmatic symptoms started between 90 and 120 minutes after the beginning of food challenges and responded to ß2-agonist therapy in a short period. In these two patients urticarial reaction and pruritus accompanied respiratory symptoms. In the control group all challenges were negative.
DISCUSSION
Many children with asthma have had foods eliminated from their diet based upon vague associations, lists of foods that supposedly cause asthma, and even based upon skin test panels of foods (3). Foods might trigger respiratory symptoms (1, 3, 4, 12, 13), or they can increase airway hyper-responsiveness without inducing acute asthma (11). They can also cause severe anaphylactic reactions. However unnecessary elimination diets will cause rapid nutritional deficiencies in young children. Therefore accurate diagnosis of food allergy is essential.
As with most medical disorders, a thorough medical history is the initial step in diagnosing adverse food reactions (2, 6). The medical history is extremely useful, especially in acute reactions, but it can be unreliable in chronic disorders such as atopic dermatitis and asthma. In several series, less than 50% of reported food-allergic reactions could be verified by isolated DBPCFCs (3, 5, 6). In our study egg and milk related asthma was proved by DBPCFCs in only 2 of 9 (22.2%) patients with positive histories of respiratory symptoms following ingestion of these foods.
The demonstration of food allergen specific IgE antibodies by prick tests or in vitro tests are commonly employed as the second step in the diagnosis of food allergy (2). Food allergen extracts currently available are not standardized, and their stabilities are usually poorly determined (1). False negative results have been reported with SPT in infants under 1 year of age (14), while false positive results are common in children with atopic dermatitis (15), and with extracts that contain irritative substances (16, 17). In recent studies the concordance between a positive prick test and positive challenge was reported to be better with fresh foods than commercial extracts, and fresh foods were proposed to be used for primary testing for egg, peanut, and cow''s milk sensitivity (18). However, in general, SPTs have been reported to have high sensitivity and negative predictive accuracy, whereas specificity and positive accuracy were poor (5, 8, 19-22). The titration of food-specific IgE is available only for certain foods, and the sensitivity of the test is not yet known for most unpurified food allergens (1, 8). No diagnostic advantage of radioallergosorbent test (RAST) alone or in combination with prick skin testing, over prick testing in the evaluation of food hypersensitivity in children was reported and RAST was proposed to be reserved for those patients for whom SPT cannot be performed (8). On the other hand, RAST may not be efficacious for diagnosing in food allergy when total IgE value is greatly elevated (23). SPTs and RASTs are sensitive indicators of food-specific IgE antibodies but poor predictors of clinical reactivity. However, in a recent study, Sampson et al (24) reported that by measuring the concentrations of food-specific IgE antibodies with CAP System FEIA, it was possible to identify a subset of patients who are highly likely to experience clinical reactions to egg, milk, peanut, or fish.
Multiscreen tests have been developed for detecting specific IgE antibodies against most common food allergens simultaneously. Adler et al (25) investigated food specific antibodies by multiple allergosorbent chemiluminescent assay (MAST-CLA) in asthmatic children and compared the results with parental perceptions, skin prick tests, and RAST results. MAST-CLA was discrepant with RAST and/or skin tests in 27.6% of the subjects. The poor correlation between the tests was probably due to the different origins of the allergen extracts used for each test. Poor stability of some allergens on the cellulose threads of the MAST-CLA pipette could contribute to poor test sensivity. On the other hand non-specific binding to the cellulose threads of the pipette may explain the positive MAST-CLA results in patients without symptoms or positive SPT and RAST. Atopic individuals sometimes demonstrate IgE sensitization without ever having had symptoms and others whose symptoms have resolved may retain detectable IgE antibodies.
Moneret-Vautrin et al (26) evaluated the use of two multitests CAP RAST fx5 and fx10 in the diagnosis of food allergy in children. The authors proposed the use of CAP RAST fx5 which is eventually to be completed by a CAP RAST, as first approach of food allergy in children. They stressed the point that prick tests have to be carried out subsequently, in order to select properly allergens responsible for food allergy.
In our study the agreement between Immulite FP5 test and oral provocation tests were 2/50 (4%). The positivity of Immulite FP5 test might be due to other food antigens included in the test panel. Since we didn''t perform oral challenges with other food extracts the correlation between FP5 test and food challenges were found to be low. On the other hand, we accepted asthmatic reactions as positive result, which differed from the other studies reported. SPT was positive in 23 patients with extracts of egg and milk, however in only 2 of 23 cases (8.70%) DBPCFC was positive. Non immune mechanisms are also responsible for food induced respiratory reactions, but we didn''t observe any asthmatic reactions in patients whose SPTs were negative.
Since there are not currently available well standardized commercial extracts and the immunologic parameters are not correlated with clinical findings, DBPCFC appears to be the best method used for diagnosing food allergy, as first reported by May (27) in mid 1970''s. However, DBPCFC is time consuming for both the patient and physician and is without risk (24). Therefore DBPCFC must be performed in a hospital, where emergency care is immediately available, and therefore must be restricted to limited cases and very selected conditions.
Novembre et al (4) screened asthmatic patients by clinical histories, skin testing, RAST analyses, and blinded food challenges. Of 140 asthmatic children evaluated, 8 (5.7%) had documented positive oral food challenges, including wheezing.
Onorato and colleagues (1) investigated 300 asthmatic patients (7 months-80 years). A total of 25 patients had either a history or skin tests or RAST suggestive of food allergy, and 20 of these patients underwent blinded food challenges. Documented wheezing was recorded in six (2%) of cases.
Oehling and colleagues (28) diagnosed food induced bronchospasm in 8.5% of 284 asthmatic children evaluated. In 74.8% of cases, a single food (especially egg) was responsible for the positive food challenge.
Bock (3) reviewed respiratory reactions confirmed by food challenges in children evaluated over an 18-year period. Of 410 asthmatic children with histories of adverse reactions to foods, 279 presented a history of one or more foods triggering asthma. Of the 279 subjects evaluated for food induced asthma, 67 (24%) exhibited wheezing as one of the symptoms elicited, but only five patients (2%) had wheezing as an isolated symptom. No delayed or late-phase asthmatic reactions were seen during DBPCFC.
In a study of 320 patients (6 months to 30 years) with atopic dermatitis and food allergy, James and his group (13) provoked respiratory symptoms, including wheezing, in 17% of these patients receiving double-blind, placebo-controlled food challenge. However, clinically significant bronchospasm (decrease in FEV1) was rare, and no late phase asthmatic response was observed.
In most clinical studies investigating the role of food allergens in asthma, the results of the food challenges varied depending on the age of the patients, the population studied, the clinical diagnosis, the number of the food allergens tested, the time of observation after the challenge, and evaluated target organ.
In our study asthma was reproduced by food challenges in two subjects only, and late asthmatic reactions were not seen. However, it must be kept in mind that, food-induced allergic reactions can increase airway hyperresponsiveness and may do so without inducing acute asthmatic symptoms or spirometric changes (11). Some food allergens must always be tested in a wheezing infant even if the infant is exclusively breast fed since allergenic foods eaten by the mother can be transferred into the breast milk (29), or the child can be sensitized in utero (30).
As a conclusion, we can say that foods can trigger asthma. However, the incidence is low even in patients whose food screening tests were positive. In our study, the incidence was proved to be low in an age group in which food allergens were suggested to have more important role in asthma. However, in order to avoid unnecessary diet restrictions, history or specific IgE tests must be confirmed by food challenges in suitable conditions. In future the new techniques for in vitro testing and better purified and standardized allergen extracts for prick testing may be helpful in diagnosing IgE mediated food reactions.
RESUMEN
Existe una percepción de que la ingestión de determinados alimentos puede agravar síntomas asmáticos. Este estudio fue realizado para determinar si la ingestión de leche de vaca o huevo puede inducir síntomas respiratorios en niños asmáticos. Se estudiaron 50 niños asmáticos de edades comprendidas entre los 1,5 y 6 años, con resultados positivos a la prueba Immulite Food Panel FP5. El grupo de control incluyó 50 niños sanos de la misma edad. Se midió la concentración de IgE total en suero y se realizaron pruebas cutáneas con alergenos alimentarios, incluyendo leche y huevo. Todos los sujetos se sometieron a prueba de provocación oral con huevo fresco y leche de vaca en polvo en condiciones de doble ciego y control por placebo. Dos historias clínicas fueron confirmadas por una prueba de provocación doble ciego y controlada por placebo en 9 pacientes (22,2%). Las pruebas cutáneas fueron positivas en 9 pacientes (18%) para antígeno de leche y en 18 pacientes (36%) para antígeno de huevo. Dos niños presentaron sibilancias, uno después de ingerir leche y el otro después de la prueba de provocación con huevo (4%). Los niños del grupo control no presentaron reacciones positivas a las pruebas de provocación con huevo o leche. Nuestros resultados confirman que las alergias alimentarias pueden acompañarse de síntomas asmáticos en niños, pero su incidencia es baja, incluso en alergenos tan importantes como el huevo y la leche. La historia clínica, determinaciones de IgE específica y pruebas cutáneas no son métodos fiables para diagnosticar las reacciones alimentarias. Por otro lado, como cualquier restricción de alimentos puede originar deficiencias rápidamente en la infancia, éstas no deben ser aplicadas sin haber realizado una prueba de provocación doble ciego, controlado con placebo.
Palabras clave: Alergia. Asma en niños. Leche de vaca. Huevo.
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