Accidental allergic reactions in children allergic to hen's egg.

BACKGROUND: Hen's egg is one of the main causes of food allergy in children. Accidental exposure is common in food-allergic patients. However, the few studies that analyze this problem focus mainly on peanut allergy. We sought to calculate the frequency of accidental exposure reactions in children allergic to hen's egg during a 12-month period, to analyze the clinical characteristics and circumstances surrounding the reactions, and to identify risk factors for the most severe reactions. METHODS: Ninety-two egg-allergic children (55 boys; median age, 52 months) were included in the study. A systematic questionnaire about accidental exposure was administered. Reactions were classified as mild, moderate, and severe. Egg white-specific immunoglobulin (Ig) E antibody titers were determined. RESULTS: Nineteen (21%) children had 24 reactions in the previous year (42% mild, 50% moderate, and 8% severe). Most reactions took place at home (50%) under routine circumstances (83%). Children with severe or moderate reactions had higher specific IgE levels to egg white (adjusted odds ratio for every 0.1-unit increase in the decimal logarithm, 1.15; 95% CI, 1.03-1.28; P = .008) and lower serum total IgE (adjusted odds ratio for every 1-unit increase in the decimal logarithm, 0.16; 95% CI, 0.05-0.54; P = .001) than those children with mild or no reactions. CONCLUSIONS: Reactions to accidental exposure are frequent in children with egg allergy. The proportion of severe or moderate reactions was 58%. The risk factors for such reactions included high titers of specific IgE to egg white and low titers of serum total IgE.

Phosphorylation reduces the allergenicity of cow casein in children with selective allergy to goat and sheep milk.

This study aimed to characterize the role of phosphorylation of caseins in selective allergy to goat milk (GM) and sheep milk (SM) in patients with good tolerance to cow milk (CM). We performed skin prick tests with milk and caseins from CM, GM, and SM and immunoblotting and specific immunoglobulin (Ig) E determinations with milk and casein from cow and GM and SM. Sensitization to milk and caseins from goat and sheep was demonstrated in all 3 patients by skin tests, determination of specific IgE, or both. Immunoblotting confirmed that GM/SM proteins but not CM proteins were involved in the allergic symptoms. IgE reacted with several protein bands from the caseins and milk extracts of both sheep and goat. Phosphorylation was involved in the different allergenicity of CM caseins. We report the implication of phosphorylation in the allergenicity of caseins involved in selective allergy to GM and SM.

Validity of specific IgE antibodies in children with egg allergy.

BACKGROUND: The demonstration of specific IgE antibodies to egg supports the existence of allergy to this food, but a correct diagnosis can only be obtained after a challenge test. Several studies have assessed different cut-off points in the level of these antibodies as predictors of clinical reactivity. OBJECTIVE: Validation of the specific IgE antibodies measured by the CAP System Fluorescence enzyme immunoassay (FEIA) technique in the diagnosis of egg allergy in children under 2 years of age. METHODS: A prospective study of 81 children with suspected egg allergy was performed. Specific IgE antibodies was quantified for egg white, egg yolk, ovoalbumin and ovomucoid. The diagnostic challenge test was carried out following the previously established criteria. The validity of the specific IgE antibodies was analysed using children with a negative diagnostic challenge test as control group. RESULTS: The prevalence of egg allergy in the group studied was 79% and egg white was the allergen that showed the greatest diagnostic efficacy. The sensitivity and positive predictive value of the prick test and of the CAP to egg white were excellent and the specificity and the negative predictive value had lower values. A level of > or = 0.35 KU(A)/L for specific IgE antibodies to egg white predicted the existence of reaction in 94% of the cases. CONCLUSIONS: Quantification of the specific IgE antibodies to egg white is useful in the diagnosis of egg allergy. In children under 2 years of age with a background of immediate hypersensitivity after egg ingestion and presence of specific IgE antibodies to egg white of > or = 0.35 KU(A)/L, diagnostic challenge test is not necessary to establish the diagnosis of allergy to this food.

Specific IgE levels in the diagnosis of immediate hypersensitivity to cows' milk protein in the infant.

BACKGROUND: A milk-free diet with substitute formula should be established when immediate symptomatic hypersensitivity to cows' milk protein (CMP) is diagnosed, and therefore an accurate diagnosis is very important. OBJECTIVE: This study aims to find the optimal cutoff values for specific IgE antibody levels that discriminate between allergic and tolerant infants by using cows' milk and its principal proteins as allergens. METHODS: A prospective study was carried out on 170 patients under 1 year old (mean, 4.8 months). These patients were seen consecutively over a 4-year period in our outpatient clinic and for the first time because of a reaction suggesting immediate hypersensitivity after ingestion of cows' milk formula. A clinical history, prick test with cows' milk and its proteins (alpha-lact-albumin, beta-lactoglobulin, and casein), determination of specific IgE antibodies with the CAP system FEIA for the same allergens as for the prick test, and a challenge test according to the diagnostic protocol were performed in all of the children. A study of validity of the prick test (cutoff point, 3 mm) and CAP system by using different cutoff points in the specific IgE values for cows' milk and its proteins were also analyzed. RESULTS: Prevalence of immediate symptomatic hypersensitivity to CMP in this study was 44%. When both the whole milk and its principal milk proteins were used in the prick test, the negative predictive value was very high, and a negative value excluded allergy in 97% of the patients. When the different cutoff points of the specific IgE for milk were analyzed, 2.5 KU(A)/L had a positive predictive value of 90% and 5 KU(A)/L had a positive predictive value of 95%. CONCLUSIONS: When diagnosing immediate hypersensitivity to CMP in infants, negative skin test responses exclude allergy in most of the patients. If the prick test response is positive, specific IgE levels for cows' milk may be helpful. If these values are 2.5 KU(A)/L or greater, the challenge test should not be performed because of its high positive predictive value (90%).

Evaluation of drug-related hypersensitivity reactions in children.

Patients with drug reactions are often referred to allergists for "allergy". Skin testing and clinical history seem to have a good negative predictive value, however, although drug challenge could be dangerous, it is the only way to confirm the diagnosis. We aimed to demonstrate that most children with a history of non-life-threatening drug reactions do not have a true drug allergy and examined the use of drug challenge in childhood. Patients with reactions were referred to our clinic by pediatricians. In 1 year, 354 reactions were studied in 239 children. Patients were classified according to their positive or negative history of drug allergy. Skin prick testing was done in all cases. Exclusion criteria for challenge included drug anaphylaxis, Stevens-Johnson syndrome, systemic reactions with severe concomitant illness, beta-inhibitor drug therapy or positive skin test to the implicated drug with a positive history. It was found that the beta-lactam antibiotics were involved in 50% of suspected reactions, aspirin in 10% and sulfonamides in 9%. Histories were considered positive only in 25%. Drug challenges confirmed only 4% of all reactions. It was concluded that drug challenge may be the gold standard for most childhood reactions that are considered to be allergic, non-life-threatening and drug-related. Only 4% of these suspected reactions were exclusively caused by drug allergy.

Relationship between pollinosis and fruit or vegetable sensitization.

The prevalence of vegetable sensitization in children with pollinosis (Group A; n = 48) and the prevalence of pollen sensitization in children with fruit or vegetable allergy (Group B; n = 42) were studied by means of prick-test and determination of serum specific IgE to several pollens, fruits and vegetables. Fifteen patients from Group A (31%) showed sensitivity to fruits and/or vegetables, but only three of them had any symptoms after ingestions. Twenty nine patients from Group B (69%) showed pollen sensitization, mainly to grass and Compositae pollen. An association was found between sensitivity to Compositae pollen and sensitivity to several fruits and vegetables (Compositae, Fagaceae, Brassica, Betulaceae and Leguminoseae).

Urticaria induced by caffeine.

Caffeine has rarely been reported as the cause of allergic reactions. We describe a 10-year-old child who developed urticaria after the intake of coffee and cola beverages. The prick test and the oral challenge test with caffeine were both positive. Nevertheless, the oral challenge test with theophylline, another methylxanthine, was negative.

Asthma with sulfite intolerance in children: a blocking study with cyanocobalamin.

Sulfites have been implicated as the cause of bronchospasm in some subjects with asthma. However, there is still no universally accepted explanation of the pathogenesis of these reactions. We have studied five children with asthma with metabisulfite intolerance confirmed by oral challenge testing. The challenge test with metabisulfite was repeated after premedication of all the patients with 1.5 mg of oral cyanocobalamin. In four of the five patients treated with cyanocobalamin, bronchospasm did not develop in the second metabisulfite challenge. The possible mechanisms are discussed.