Clinically, if the big toe is blackened, the first thing to look for is whether it is one toe or multiple toes at the same time and whether the fingers have similar symptoms. Clinically, we should observe whether there is localized numbness and pain in the toes after the big toe becomes black. In particular, the numbness is uncomfortable after activity. If similar symptoms of appeal occur in one toe unilaterally, it is considered to be caused by insufficient arterial blood supply. This is especially true if the patient has high-risk factors for atherosclerosis, such as hypertension, diabetes, and long-term smoking. Similar symptoms can occur if there is an impaired blood supply to the arteries of the big toe. Severe cases require treatment with possible amputation, and mild cases may require surgical intervention for revascularization. Other clinical infectious diseases can cause blackening of the big toe, such as fungal infections, commonly known as gray nails, which can present with similar symptoms. Such patients usually present with similar symptoms in the other toes in addition to the big toe. Clinical treatment with antifungal drugs must first be clearly diagnosed then standardized with fluconazole, voriconazole, etc. to achieve good results.