There is a reduction of alpha 1-antichymotrypsin as seen in some other forms of urticaria, and eruption is improved with danazol. This has prompted some to argue for proteases as a cause of histamine release. While mast cell release seems to be involved, there is less eosinophilic, major basic protein than in many other forms of urticaria. One report showed positive immediate sensitivity to sweat with passive transfer. Some investigators, but not others, have reported positive passive transfer.
Autonomic functions are normal.
One patient developed an accentuated response in a positive copper test site, perhaps from vasodilatation or perhaps augmentation of neurologic stimulation. In one study muscarinic receptors were reduced but binding was normal. Thermography ostensibly shows the areas of involvement. Treadmill exercise produces a sensation of generalized skin warmth, followed by pruritus, erythema, urticaria, and transient respiratory tract symptoms consisting of shortness of breath or wheezing or both. Rise in residual volume was also detected.