Mainly due to exercise, heat, mental stress, eating hot drinks or alcoholic drinks, the deep body temperature rises, prompting acetylcholine to act on mast cells and get sick. It is characterized by the appearance of round papules with a diameter of 2 ~ 4 mm several minutes after stimulation, with different degrees of redness around them, which are often distributed in the upper torso and upper limbs and do not merge with each other. Conscious itching, tingling or burning sensation, sometimes only severe itching without skin lesions, can disappear within 0.5 ~ 1 hour. Occasionally accompanied by general symptoms caused by acetylcholine (such as salivation, headache, bradycardia, miosis, spasmodic abdominal pain and diarrhea), severe dizziness can cause syncope. 1:5000 When acetylcholine is used for skin test or scratch test, wheal can appear at the injection site, and small satellite wheal can appear around it.