Miconazole nitrate can cause several unpleasant side effects. They are usually limited to the area of application and can include burning, cramping, hives, skin irritation, vulval itching, rash and vaginal itching. This drug can also cause headaches, so it should be used with caution. Allergic reaction can occur and may involve redness, swelling and irritation. Seek medical attention if an allergic reaction causes swelling of the lips and tongue or difficulty breathing.