Identification of IgE-mediated food allergy and allergens in older children and adults with asthma and allergic rhinitis.

Background and objective. Prevalence of immunoglobulin (Ig) E-mediated food allergy is primarily reported for certain pediatric populations and adults. The present study was aimed to investigate the relative prevalence of food allergy and allergens in older children and adults with asthma and allergic rhinitis. Methods. Patients (12-62 years) were screened using standard questionnaire and skin prick-test (SPT) with common foods and aeroallergens. Specific IgE level was determined by enzyme linked immunosorbent assay (ELISA) and allergy was established by blinded food challenges. Results. Of 1860 patients screened, 1097 (58.9%) gave history of food allergy. Of the history positive patients skin tested (n=470), 138 (29.3%) showed a marked positive reaction to food extracts. Rice elicited positive SPT reaction in maximum number of cases 29 (6.2%) followed by blackgram 28 (5.9%), lentil 26 (5.5%), citrus fruits 25 (5.3%), pea 18 (3.8%), maize 18 (3.8%) and banana 17 (3.6%). The SPT positive patients showed elevated specific IgE levels (range: 0.8-79 IU/mL) against respective food allergens than normal controls (0.73 IU/mL, mean±2SD). Food allergy was confirmed in 21/45 (46.6%) of the patients by blinded controlled food challenges. The prevalence of food allergy was estimated to be 4.5% (2.6%-6.34%) at 95% confidence interval (95% CI) in test population (n=470). Sensitisation to food was significantly associated with asthma (p=0.0065) while aeroallergens were strongly related to rhinitis (p<0.01). Conclusions. Food allergy is estimated to be 4.5% in adolescents and adults with asthma, rhinitis or both. Rice, citrus fruits, blackgram and banana are identified as major allergens for inducing allergic symptoms.

Relevance of serum IgE estimation in allergic bronchial asthma with special reference to food allergy.

Studies suggest the importance of serum total and specific IgE in clinical evaluation of allergic manifestations. Such studies are lacking in Indian subcontinent, though a large population suffer from bronchial asthma. Here relevance of serum total and specific IgE was investigated in asthmatics with food sensitization. A total of 216 consecutive patients (mean age 31.9 years, S.D. 11.8) were screened by various diagnostic testing. Out of 216 patients, 172 were with elevated serum total IgE (201 to > 800 IU/ml). Rice elicited marked positive skin prick test reactions (SPT) in 24 (11%) asthma patients followed by black gram 22 (10%), lentil 21 (9.7%) and citrus fruits 20 (9.2%). Serum total IgE and specific IgE showed significant correlation, p = 0.005 and p = 0.001, respectively, with positive skin tests. Blinded food challenges (DBPCFC) with rice and or black gram confirmed food sensitization in 28-37% of cases. In summary, serum total IgE of 265 IU/ml or more with marked positive SPT (4 mm or more) can serve as marker for atopy and food sensitization. Specific IgE, three times of normal controls correlates well with positive DBPCFC and offers evidence for the cases of food allergy.