Specific sensitization to Dermatophagoides pteronyssinus and cutaneous reactivity to histamine in Brazilian children

The immediate hypersensitivity cutaneous test is a recognized method for etiologic diagnosis of allergic diseases. It is easily conducted, painless and can be quickly interpreted, making it deal for use with children. However, its low positivity in infants limits its use this population. The purpose of our study was to evaluate the skin reactivity to atopic and non-atopic children of different ages to increasing concentrations of histamine and to an extract of Dermatophagoides pteronyssinus (Dpt). Atopic children (A, n = 217) and non-atopic children (C, n = 198), under 15 years of age were grouped by age and administered skin prick tests. Increasing concentrations of histamine (1, 9, 81 and 243 mg/ml) and Dpt (10,000 AU/ml) were applied to the forearm. Skin reactions were recorded after 15 minutes and expressed as the mean of the largest wheal and its midpoint perpendicular diameter. Cutaneous reactions were observed in the early phases of life with a progressive increase observed in both groups. Significant differences were noted between the two groups starting at 48 months of life. As the concentration of histamine was increased, we observed a higher level of cutaneous reactivity in younger children. Comparative analysis of cutaneous reactivity to the histamine solution (1 mg/ml) and the Dpt extract showed parallelism between them and wheals with diameters larger than 3 mm after 12 months of age. We concluded that the skin prick test with Dpt is reliable in atopic children after 1 year of age. Reactivity to higher concentrations of histamine was observed after 3 months of age for all children. However, considering all age groups, the skin reactivity in atopic children to histamine (1 mg/ml) was more precocious when compared to controls.