The bulge on the leg may be caused by insect bite reaction, lipoma, folliculitis and other diseases. 1. Insect bite reaction: common in mosquitoes, mites, lice, flea bites, often occurring in the waist, buttocks and limb extensor surfaces, localized redness, swelling, blisters, erythema, firm papules and other symptoms, so the patient’s leg bulge may be the reaction to insect bites. 2. Lipoma: the etiology of this disease is not clear, often occurring in the thighs, upper arms, neck, etc., there will be obvious localized masses, which can be manifested as bulging bags on the legs. 3. Folliculitis: this disease is mainly caused by the infection of hair follicle microorganisms, such as Staphylococcus aureus. The main manifestation is a red papule centered on the hair follicle, which can occur in any area where there is hair, therefore, the patient will have a bulge on the leg. Patients with bulging legs are advised to visit a hospital to determine the exact cause.