The main reasons for a sudden, hard and painful swelling of the chin include the following: First, it is considered to be caused by swollen lymph nodes in the neck, mostly due to acute lymphadenitis. The chin is distributed with a large number of lymph nodes, if due to the recent decline in body resistance, or eat more spicy and stimulating food, etc., will stimulate the lymph nodes in the neck reactive hyperplasia, enlargement caused by acute lymph nodes, and then cause the chin suddenly swollen and very hard, very painful, etc.. It can be clarified by going to the quintuplegia department of the hospital and doing ultrasound examination of the neck, and it needs to be treated with the application of antibacterial drugs for symptomatic anti-inflammation. Secondly, it is considered to be caused by the infection of soft tissue boils on the chin, mostly due to the recent decline in resistance and other causes of subcutaneous soft tissue infection on the neck, and then the formation of subcutaneous boils and sudden swelling of the chin and very hard and painful. If the boil has become pus or an abscess has formed, an incision and drainage will be required.