A study of allergen-specific IgE antibodies in Indian patients of atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) is a chronic, relapsing, pruritic dermatitis frequently associated with the hyperproduction of IgE to various allergens. Identification of these allergens is possible by various laboratory investigations. AIM: The present study was designed to assess these allergen-specific antibodies in the diagnosis of AD in the Indian context. METHODS: This prospective study comprised 50 patients of AD. The diagnosis was made clinically after satisfying Hanifin and Rajka's criteria. Serum IgE levels were estimated and specific IgE antibodies were measured for 20 food allergens and aeroallergens. RESULTS: Serum IgE was elevated in 88% of the patients. The highest elevation of mean IgE levels was seen in the 10-20 years age group. Sixty five percent of the children under the age of ten years were positive to one or more food allergens. Food allergens were more often positive in the < or = 10 years age group and specific antibodies to inhalants were seen more frequently in the older age groups. Specific antibodies to apples were found in all age groups. CONCLUSION: Antibodies against apples and hazelnuts were the more commonly seen specific antibodies in children. Incidence of positivity was much higher in children when compared to earlier studies. Identification of food allergens can be an important factor in the diagnosis of AD in children in India. Positivity to inhalant allergens in the older age groups was lower in this study. The allergen profile with regard to inhalants in Indian patients was similar to that of earlier studies.

Skin manifestations and immunological parameters in childhood food allergy.

According to Hansen's contact rule, the digestive system should be considered as the main shock organ, yet in food allergy, this is not the case. Very often specific food triggers clinical manifestations not involving the digestive system; that is, reactions are manifested either in the respiratory system, as asthma or rhinitis, or in the skin. In these cases the BALT (broncho-alveolar lymphoid tissue) and GALT (gastrointestinal lymphoid tissue) units play a basic role in the sensitizations. The purpose of this study was to determine the most frequent skin manifestations of food allergy among children, and the most frequently involved foods. We also thought it interesting to evaluate the diagnostic reliability of the different standard immunological parameters utilized by the study team in food allergy. All patients underwent intracutaneous tests with 12 groups of the most frequent food allergens, as well as serum IgE, antigen-specific IgE against foods, and antigen-specific histamine release tests. Antigen-specific IgG4 determination was performed in some cases. The results obtained confirmed previous studies, the most common manifestations being: angioedema (48%), followed by urticaria (31%) and atopic dermatitis (21%). Regarding the frequency of sensitization to different food allergens, in mono- or polisensitization, fish and egg stand out in our environment. Certain food allergens are more frequently responsible for specific skin manifestations. Thus, for fish sensitization, the most frequent skin manifestation is atopic dermatitis (50%); for egg sensitization, angioedema is the most frequent skin manifestation (50%); and for milk, urticaria (50%). Finally, and in agreement with previous works regarding the diagnostic reliability of in vitro techniques, we found that the histamine release test offered the highest percentage of diagnostic reliability. Only for sensitization to milk proteins did antigen-specific IgE demonstrate higher reliability. Once again, we stress that our main problem is the lower reliability of skin tests against food allergens than against inhalant allergens. We emphasize the importance of food as a major factor in the etiopathogenesis of atopic dermatitis, as well as the need to complement the study, when possible, by means of the in vitro techniques described.