Eli5: Why is one of the causes of urticaria cold temperatures?


How can temperature cause an anaphylactic reaction? Is it something already in the skin that reacts to the cold?

In: 1

from http://www.mayoclinic.org/diseases-conditions/cold-urticaria/symptoms-causes/syc-20371046:

No one knows exactly what causes cold urticaria. Certain people appear to have very sensitive skin cells, due to an inherited trait, a virus or an illness. In the most common forms of this condition, cold triggers the release of histamine and other chemicals into the bloodstream. These chemicals cause hives and sometimes a whole-body (systemic) reaction.

I can also add that histamine is what causes allergy symptoms (many allergy medications are anti-histamines). Urticaria is a common symptom of allergy.