An Update and Review

physical urticarias are a unique subgroup of chronic urticarias in which wheals can be repeatedly induced by various physical stimuli. Heat, cold, pressure, light, increase in core body temperature, water, and vibration have all been implicated as the provoking stimuli in certain patients. To the clinician, these conditions are of interest because they may represent from 77c to 17% of the cases of chronic urticaria.' The frustrated clinician must cope with being unable to identify provoking stimuli in up to 80% of the cases of chronic urticaria.' Therefore, the physical urticarias are diagnosable entities not to be missed. The clinical investigator is challenged by the reproducibility of lesions in these patients, facilitating sequential sample collection for immunologie and pharmacologie studies. The physical urticarias are united as a group and are distinguished from other forms of chronic urticaria by their frequent occurrence in young adults, the short dura¬ tion of their episodic lesions, the sharp limitation of these lesions to the areas of physical stimuli, the tendency not to occur at night, the inducibility by physical stimuli, and their general unresponsiveness to corticosteroids given for systemic effect.'Two important reviews by Duke3-4 appeared in the 1920s on physical allergies as causes of dermatoses. He carefully observed patients with solar urticaria (urticaria Solaris), cold urticaria (hiemalis), dermatographism or mechanical irritation urticaria (dermographica), mental and physical exertion and heat urticaria (calorica), and heat contact urticaria (ab igne) and established a framework for classi¬ fication and discussion of the physical urticarias. These disorders vary greatly in their relative frequency of occurrence. Warin and Champion- reviewed 554 cases of urticaria and reported that 8.5% were symptomatic derma¬ tographism and 5.1% were cholinergic urticaria; all other physical urticarias constituted 3.4% of the cases. They also stressed that, in some patients, more than one type of physical urticaria may coexist. For example, cholinergic