Increased skin temperature is commonly associated with erythermalgia. Erythromelalgia is a disorder caused by excessive vasodilation of the extremities and is characterized by paroxysmal redness, increased skin temperature and burning pain in a warm environment. Primary cases are more common. It is a rare disease. Patients are mostly children or 40 years old. In the 433 cases reported in Guangzhou, young women were the most common, accounting for 92.86%, with a male to female ratio of 1/13. Diagnosis: The disease is most common in young adults aged 20 to 40 years, with more males than females, and can be acute or chronic, involving both extremities at the same time, with both feet being more common. It is characterized by redness of the toes, soles, fingers and palms, increased arterial pulsation, increased skin temperature, and unbearable burning pain. The pain is usually worse at night and lasts for several hours. Heat, elevated ambient temperature, movement, standing, foot drop or stroking of the affected limb can lead to clinical attacks or increased symptoms; rest, elevation of the affected limb, exposure of the affected limb to cold air or immersion in cold water can reduce or relieve the pain. Patients are reluctant to wear shoes and socks and to put their limbs under the covers, and are afraid of medical examination. There may be objective sensory loss, thickened finger (toe) nails, and muscle atrophy, but rarely ulceration or gangrene of the extremities. In long and/or severe cases, symptoms are not limited to the extremities, but may extend to the entire lower extremity and involve the upper extremity. The diagnosis can often be made by the paroxysmal appearance of redness, swelling, heat and pain in both feet under certain triggers. Based on the characteristic clinical manifestations, the diagnosis of erythema limbosum is not difficult. The disease is approximately 60% primary. The others can be caused by true erythrocytosis, hyperthyroidism, systemic lupus erythematosus, hypertension, alcoholism, pernicious anemia, thrombo-occlusive vasculitis, gout, rheumatoid arthritis, venous insufficiency, peripheral neuritis associated with diabetes, as well as thallium, mercury or arsenic poisoning and pellagra, which are called “secondary erythematous limb pain. This is called “secondary erythematous limb pain”. Differential diagnosis of elevated skin temperature: 1. Temporary erythematous limb pain Vascular disease after complete arterial bypass grafting, with the restoration of distal perfusion pressure, there can be significant reactive congestion in the ischemic area. This phenomenon is called “transient erythema limbosum” and may last for several days or even weeks. Fever (feVer, pyrexie) is a pathological increase in body temperature, which is caused by the upward shift of the thermoregulatory center of the body in response to the action of thermogenic agents, and is the most common clinical symptom and an important clinical manifestation in the process of disease progression. It can be seen in a variety of infectious and non-infectious diseases. It has a typical fever pattern and course, specific clinical features, and is generally easy to diagnose; however, some patients with fever have a long fever duration, no specific signs, and lack of information with diagnostic significance, and are often called fever of unknown origin (FUO). After clinical observation and special examination, most of them can finally be diagnosed clearly, but in about 10% of patients, the diagnosis is still not clear despite various examinations, and the course of the disease is delayed for several months. 3.Flaccid fever Flaccid fever means that the body temperature is persistently above 39 degrees, with large fluctuation, and the temperature fluctuation range is more than 2 degrees within 24 hours, but all of them are above the normal level. 4.Persistent fever When the oral temperature is higher than 37.3℃ or the anal temperature is higher than 37.6℃, and the change between one day is more than 1.2℃, it is called fever. According to the level of fever, the following clinical gradations can be distinguished: low fever 37.4℃～38℃ moderate fever 38.1℃～39℃ high fever 39.1℃～41℃ super high fever 41℃ or more, lasting for more than 4 weeks, is persistent fever. 5.Central fever Central fever refers to fever produced by abnormalities in the thermoregulatory center due to central nervous system lesions. 6, heart fire Heart fire in Chinese medicine refers to the internal heat of the human body. It is often manifested as the five hearts are irritable and hot, dry throat, dry mouth, mouth and tongue sores and other symptoms. Chinese medicine has the heart in the ground for the fire said so called. 7, irregular fever Some febrile diseases have their own special heat type, which occurs in the extreme stage of febrile diseases. The fever type has certain clinical significance in diagnosis and differential diagnosis. Irregular fever means that the fever is not regular and does not last for a certain period of time. It can be seen in a variety of pulmonary diseases, cardiothoracic pleurisy. Patients are advised to wear porous sandals, the feet should not be covered during nighttime sleep, and the feet should avoid exposure to warmth, especially dry heat, as much as possible. Those with heavy seizures can move to a place where the temperature does not reach below the critical temperature that causes painful attacks. However, it is not advisable to use ice or ice water local cooling methods to relieve the attack, so as not to damage the blood vessels and peripheral nerves of the extremities, but to sustain or aggravate the attack.