Since the beginning of summer, there has been a significant increase in the number of patients with dermatophytosis, especially in the lower extremities. Patients often present with localized skin redness and swelling of the lower legs, increased skin temperature, and in some cases, significant burning-like pain and generalized fever. Patients who come to the clinic often suffer from tinea pedis, or have localized skin breakdown, or have a decreased immune system due to exertion. In order to assist patients to clarify the principles of diagnosis and treatment of this disease, the causes, clinical manifestations and our experience in diagnosis and treatment are summarized as follows: Dermatophytosis is an acute inflammatory infection of the lymphatic network of the skin, caused by the infestation of Streptococcus hemolyticus type B. The prevalent sites are the lower extremities and the face. Patients often have some kind of skin or mucous membrane lesions, such as skin injury, tinea pedis, oral ulcers, sinusitis, etc. After the onset of the disease, the skin of the lymphatic network distribution area appears inflammatory reaction, the lymph nodes in the drainage area are also often involved, the lesion spreads quickly, the systemic reaction is more severe, but there is rarely tissue necrosis or septicemia. The lesion spreads quickly and the systemic reaction is severe, but there is rarely any tissue necrosis or pus. The onset of the disease is rapid, with chills, fever, headache and general discomfort at the beginning. The lesions are mostly found on the lower extremities and appear as a flaky red rash, slightly elevated, bright red, slightly lighter in the middle, and more clearly defined. There is local burning pain, and when the lesion extends to the periphery, the central redness subsides and changes to brownish-yellow. Some of the lesions may blister, and the nearby lymph nodes are often enlarged and painful to the touch, but the skin and lymph nodes are rarely septic and ruptured. After treatment, the lymphatic vessels may become blocked and lymphatic stagnation may occur due to recurrence of the lesion. Repeated attacks of lymphatic edema in the lower extremities can lead to thick skin and swollen limbs, even developing into “elephantiasis”. Treatment: Rest in bed and elevate the affected limb. Local hot and humid compresses of 50% magnesium sulfate solution can be applied. Theoretically, penicillin is the most effective antimicrobial drug, but in actual clinical treatment, the causative organisms are often resistant or insensitive to penicillin, so many patients who come to the clinic have already applied penicillin in outside hospitals, but the effect is not obvious. Our experience is: for those with limited lesions and mild symptoms, cephalosporin antibiotics can be given to achieve good results; if the lesions are extensive or the symptoms of redness, swelling, heat and pain are obvious, cephalosporin and silicone antibiotics should be applied in combination. Adequate dosage of drugs is needed, and it often takes 1 to 2 weeks of continuous treatment to completely control the symptoms. After the local and systemic symptoms have disappeared, the patient still needs to take oral antibiotics for 1 week to avoid their recurrence. Treatment of triggering factors such as tinea pedis is required at the same time to help avoid recurrence.