Simvastatin is generally well-tolerated and side effects are rare. Minor side effects include constipation, diarrhea, fatigue, gas, heartburn, and headache. Major side effects include abdominal pain or cramps, blurred vision, dizziness, easy bruising or bleeding, itching, muscle pain or cramps, rash. This could be an allergic reaction to the drug. It will stop if the drug is withdrawn. You need to inform your doctor about this development. He might want to substitute it with another. It cannot be a time coincidence unless you had the itching prior to starting the drug. You could apply an anti-itch lotion or cold compresses on the skin to soothe the areas. If itching persists after you stop the drug for a few days, then you may take anti-histamines to treat it