Studies of atopic patch tests

35 patients were patch-tested for 72 h with house dust mite, timothy- and birch-pollen, Cladosporium herbarum and hen's egg white allergens, prepared in a cream in concentrations up to 1,000 times the concentration used for skin prick testing. 6 patients developed a total of 10 positive reactions. All the strong positive patch-test reactions occurred in patients with a strong positive skin prick test to the same allergen. Immunohistochemical studies of biopsied positive patch-test reactions demonstrated a mononuclear cell-infiltrate in the upper part of dermis, consisting mainly of T-cells, with a slight predominance of T-helper-cells as compared to T-suppressor cells, and about 10% CD1 positive cells. No significant responses were obtained in peripheral blood mononuclear cell-cultures stimulated with the various allergens. A positive patch-test reaction to birch-pollen was successfully transferred passively to a non-allergic-recipient, suggesting that the positive reaction may depend upon sensitizing factor(s) in the serum.