Spider webs under the neck are called spider nevi, which are vascular moles formed by the dilation of the end branches of small arteries in the skin. The causes of cobwebs under the neck include normal physiological reaction, viral hepatitis or cirrhosis of the liver. 1. Normal physiological reaction: during puberty or pregnancy, women’s hormone secretion is strong, and it is very likely that the phenomenon of cobwebs under the neck will occur, which is a normal physiological reaction, and it can subside on its own. 2. Viral hepatitis: it is mainly caused by various hepatitis virus infections, which can be manifested as spider nevus on the neck, fatigue, loss of appetite, nausea or vomiting, and so on. 3. Cirrhosis: mainly due to the liver blood circulation obstacle or long-term bile accumulation, the patient may not only manifest as cobweb under the neck, but also accompanied by emaciation or diarrhea and so on. There are many other causes of spider webs under the neck, it is recommended to go to the hospital in a timely manner, after clarifying the cause of the disease, under the guidance of a professional doctor for standardized treatment.