Effects of cromolyn on codeine-induced histamine release in vivo.

Cromolyn has been shown to inhibit histamine release from mast cells induced by various stimuli in vitro. However, the local effects of cromolyn on codeine-induced wheal and flare skin reactions are not well understood. Intradermal injection of codeine induced prominent whealing in almost all humans. We studied the effect of local cromolyn injection on codeine-induced skin reactions, histamine release, and ultramicroscopic changes in mast cells in 10 volunteers. The finding in this study showed that injection of a 2% cromolyn solution before or together with the codeine injection does not affect the subsequent skin reactions, histamine release and ultramicroscopic changes of mast cells.