Redness and swelling of the inner thigh along the medial side to the anterior side of the calf may be caused by lower extremity dengue, contact dermatitis, trauma and other reasons. 1. Lower extremity salpingitis: salpingitis is mostly caused by type B hemolytic streptococcus infection, which mainly involves lymphatic vessels. Bacteria can invade through the skin or mucous membrane minor injury, will cause edematous erythema, clear boundaries, the surface is tense and shiny, rapidly expanding to the surrounding. Enlargement of lymph nodes and varying degrees of systemic symptoms may occur. It may cause erythema of the inner thigh along the medial side to the anterior side of the calf. 2. Contact dermatitis: due to contact with certain easily sensitized or irritated substances lead to skin metamorphosis or irritation reaction, resulting in edematous erythema, itching and other symptoms. It can also cause redness and swelling of the inner thigh along the inner side to the front side of the calf. 3. Trauma: local skin wounds caused by external forces, accompanied by redness, swelling, tingling and other symptoms, may also lead to the inner thigh along the medial to anterior calf redness and swelling. Redness and swelling along the inner side of the inner thigh to the front of the calf, there may be other reasons, need to go to the hospital in time for further examination to confirm the diagnosis.