Studies of a family with "familial cold urticaria" indicate that the syndrome is not a true urticarial disorder, but appears to be a systemic reaction generated by cooling of the skin. The systemic reaction appears to be mediated by an unidentified humoral substance, probably not histamine. Leukocytosis is a constant accompaniment of the generalized reaction and seems to play a role in the pathogenesis of the skin lesions. The generalized reaction can be prevented by the prior administration of Pseudomonas polysaccharide complex (Piromen).
Tindall JP, Beeker SK, Rosse WF. Familial Cold UrticariaA Generalized Reaction Involving Leukocytosis. Arch Intern Med. 1969;124(2):129-134. doi:10.1001/archinte.1969.00300180001001