A case study on the induction of clinical tolerance in cold urticaria.

The mechanism(s) by which repeated cold challenge in a patient with idiopathic acquired cold urticaria resulted in the induction of clinical tolerance to cold stimuli was studied. Plasma histamine levels, mast cell ultrastructure, and the cutaneous response to intradermal injections of morphine, histamine, and substance P were examined before and after the induction of tolerance. Plasma histamine levels draining cold-challenged, clinically tolerant skin were markedly diminished compared to histamine levels obtained during cold-induced angioedema. Furthermore, electronmicroscopy of skin samples taken from tolerant skin after cold challenge revealed intact, largely normal appearing mast cells. Intradermal injection of mast cell secretagogues and vasoactive agonists into normal and tolerant skin sites resulted in similar whealing responses. Thus, these studies suggest that the state of clinical tolerance to cold stimuli is due neither to mast cell-mediator depletion or tachyphylaxis of the cutaneous vasculature to vasoactive agonists. It appears likely that tolerance may be due to the induction of a specific state of unresponsiveness of mast cells to cold stimuli or possibly to depletion of a cold-induced cutaneous antigen capable of triggering mast cell degranulation.