Cholinergic urticaria is a subcategory of physical urticaria (aka hives) that is a skin
rash brought on by a hypersensitive reaction to body heat
. Symptoms follow any stimulus to sweat such as exercise , heat from the sun, saunas, hot showers , spicy foods which may cause an increase in body temperature or even stress due to blushing or anger. Some people only have symptoms during the winter months where their body temperature rises when it is unacclimatized to heat.