A finger suddenly swollen purple may be suffering from purulent dactylitis, insect bite dermatitis, gouty arthritis and other diseases, may also be caused by trauma. 1. Purulent dactylitis: purulent dactylitis is generally caused by infection, the patient’s early finger manifested as mild to moderate swelling, redness, and accompanied by mild pain, with the development of the disease, the patient’s finger swelling aggravated and obvious tenderness, and some patients will also appear high fever, headache and other systemic symptoms. 2. Insect bite dermatitis: insect bite dermatitis is generally associated with mosquito bites, when the finger area is mosquito bites, the patient will appear early erythema, edema, with the development of the disease, the patient edematous erythema on the basis of blisters, and accompanied by intense itching. 3. Gouty arthritis: gouty arthritis is generally associated with genetic and metabolic factors, mainly purine metabolism disorders in the body and uric acid excretion disorders, the patient’s hand joints will appear obvious swelling, pain, skin reddening, elevated skin temperature and other symptoms, the majority of patients have a history of hyperuricemia or recently eat a lot of high purine food. 4. Trauma: When the finger area is impacted or squeezed by foreign objects, it may also lead to finger swelling and purple. If there are symptoms of discomfort, it is recommended to go to the hospital in time to find out the cause of the problem, and then follow the doctor’s instructions for treatment after a clear diagnosis.