On a warm summer day an apparently healthy man went for a swim in a freshwater lake. Minutes after he entered the cold water, he experienced pruritus, palpitations, and syncope. Rescued and hospitalized, he was found to have a generalized urticarial eruption, a flushed face, tachycardia, and hypotension. Recovery was complete within four hours, but subsequent application of an ice cube to his skin produced immediate local urticaria, even where cold water ran down his back (Figure).
The following differential diagnosis of cold hypersensitivity was considered:
Syphilitic paroxysmal cold hemoglobinuria.
Presence of cold hemagglutinins.
Essential cold urticaria.
A test for cryoglobulins was negative. A serologic test for syphilis was nonreactive, and cold hemolysins, present in syphilitic paroxysmal cold hemoglobinuria, were not demonstrated in the serum. Cold hemagglutinins, such as those in primary atypical pneumonia, produce problems of diminished blood supply, but do not result in