I have never heard of Botox causing blood clots in the leg or elsewhere. Some of the more common potential side effects are headache, droopy eyelid, crooked smile, dry mouth, fatigue, pain, swelling, or bruising at the injection site. Botox is very safe when properly administered. Potential risk factors for developing a blood clot in the leg (DVT) include prolonged bedrest or prolonged sitting (e.g., driving or flying), smoking, birth control pills, pregnancy, obesity, heart failure, inflammatory bowel disease, an inherited blood-clotting disorder, and cancer. Your primary care physician will be able to help in ascertaining the cause. Best regards, Dr. DuPont