Raynaudphenomenon (Raynaud phenomenon) is due to cold or emotional stimulation of the small terminal arteries of the human limb, resulting in vascular vasospasm causing distal limb ischemia and hypoxia, followed by a series of processes in the limb color change due to increased acidity and relief of vasospasm. If the artery of the finger limb encounters cold, it will spasm, and the blood flow into the limb will be greatly reduced, so the end of the limb will appear white; if the ischemia reaches a certain time, the local tissue ischemia and hypoxia will be aggravated, and the color of the end of the limb will turn cyanotic and purple, and become a state of bruising; at this time, the acid that can cause vasodilation will increase, so that the spasmodic blood vessels will relieve diastole, and the blood supply will return, then the color of the end of the limb will The color of the end of the limb returns to normal. It is common in cold areas in the north, and is more common in young women; when contacting cold water or cold objects such as laundry, the above changes occur at the ends of the fingers of the limbs, and this condition is called Raynaud’s phenomenon.